CN116134175A

CN116134175A - Method for metallizing nonmetallic substrates and pretreatment composition

Info

Publication number: CN116134175A
Application number: CN202180052417.0A
Authority: CN
Inventors: B·迪尔布施; F·芬恩; C·C·费尔斯
Original assignee: Germany Aituoteke Co ltd
Current assignee: Germany Aituoteke Co ltd
Priority date: 2020-08-25
Filing date: 2021-08-23
Publication date: 2023-05-16
Also published as: JP2023539605A; US20230357932A1; WO2022043241A1; KR20230054853A; CA3190838A1; BR112023003111A2; EP4204601A1

Abstract

The invention relates to a method for metallizing a nonmetallic substrate, comprising steps (a) to (C), wherein step (a) is a pretreatment step for etching, and step (C) is a metallizing step. In step (a), a pretreatment composition comprising individual manganese (II), (III) and (IV) species is utilized. The invention also relates to a specific pretreatment composition.

Description

Method for metallizing nonmetallic substrates and pretreatment composition

Technical Field

Background

Nonmetallic substrates such as plastic substrates have a long history in modern technology. Typical applications are in the automotive industry and in sanitary applications.

However, there is a high demand for non-metallic/non-conductive substrates to be able to accept metallic layers. Generally, the corresponding method is to first surface modify the substrate surface, commonly referred to as etching. Typically, a sensitive balance is required to ensure adequate surface roughening without causing too strong defects.

Many methods and etching compositions are known, including compositions comprising environmentally problematic chromium species (e.g., hexavalent chromium species). While these compositions generally provide very strong and acceptable etching results, there is an increasing need for environmentally friendly alternatives and to some extent they have been provided in the art.

For example, WO 2018/095998 A1 mentions a chromium-free etch for plating in a plastic process, wherein the plastic surface is contacted in a first step with an etching solution comprising at least Mn (IV) ions, in a second etching step with a solution comprising at least Mn (III) and Mn (VII) ions, followed by a plating step.

EP 3 584,352 A1 mentions a pretreatment composition for electroless plating and a corresponding pretreatment method which exhibit higher plating deposition performance without using harmful chromic acid and expensive palladium while reducing the number of steps.

EP 0 913 498 A1 mentions a process combining surface treatment and metal deposition. The corresponding aqueous solution contains a metal activator such as an oxidizing species of silver, cobalt, ruthenium, cerium, iron, manganese, nickel, rhodium or vanadium. The activator may suitably be electrochemically oxidized to a higher oxidation state.

EP 2 025 708 A1 mentions an etching solution comprising manganese (VII) ions.

EP 2 937 446 B1 mentions a composition for etching treatment of resin materials, said composition comprising permanganate ions.

US 2017/159483 A1 mentions a resin plating method using an etching bath containing manganese as an active ingredient.

US 8,603,352 B1 mentions a chromium-free composition of an acidic suspension of a manganese compound and manganese ions are applied to the organic polymer surface to etch the surface. The suspension comprises one or more undissolved manganese (II) compounds, or one or more undissolved manganese (III) compounds, or a mixture thereof, dissolved manganese (II) ions and dissolved manganese (III) ions, and one or more acids.

CN 110172684A mentions the formulation and preparation of a chromium-free roughening solution for ABS plastic.

As seen above, in many cases manganese species are utilized in place of chromium ions. However, certain manganese species have specific drawbacks themselves. For example, manganese (VII) species often form difficult to handle manganese dioxide, which often adsorbs to the substrate surface and requires chemical reduction to dissolve it.

In addition, in addition to the environmentally problematic chromium ion problem, the etching process also affects the overall quality of the subsequently deposited outermost metal layer, in particular in terms of gloss/brightness and surface roughness. This is especially true if the outermost metal layer is a chromium layer. Since the optical appearance of the outermost metal layer needs to be as perfect as possible, a suitable metallization process starts with a well-balanced etching step.

Object of the invention

It is therefore an object of the present invention to overcome the above-mentioned drawbacks of the prior art.

It is a particular object of the present invention to provide a method for metallizing a non-metallic substrate, wherein the obtained metallized substrate, in particular with a chromium layer, provides a still further improved quality. It is particularly desirable to obtain a metallic layer (particularly a chromium layer) that is very smooth and has improved metallic luster/brightness, yet still adheres adequately to non-metallic substrates.

It is a further object of the present invention to provide a process comprising a single pretreatment step, in particular in the absence of a chemical reduction step.

Another object of the invention is to provide a method which is less dependent on substrates with high manufacturing quality, but which also allows for a uniform pretreatment and metallization of substrates of lower manufacturing quality, in particular substrates comprising polybutadiene.

Disclosure of Invention

The above object is solved by a method for metallizing a non-metallic substrate, said method comprising the steps of

(A) Contacting the nonmetallic substrate with a pretreatment composition, thereby obtaining a pretreated substrate,

wherein the pretreatment composition comprises

(A-a) individual manganese (II), (III) and (IV) species,

(B) Contacting the pretreated substrate with an activating composition to obtain an activated substrate, and

(C) Contacting the activated substrate with one or more than one metallization composition, thereby obtaining a metallized substrate,

provided that it is

In the pretreatment composition, the total concentration of manganese (IV) species is higher than the combined concentration of manganese (II) and (III) species,

-applying an electric current to the pretreatment composition such that the manganese (II) species is oxidized to a manganese (III) species, and

-in step (a), contacting the substrate with a manganese species is performed in a single step.

The present invention is based primarily on the specially designed pretreatment composition used in step (a); most preferred is for nickel plating in step (C) in combination with a metallization composition comprising nickel. The specially designed pretreatment compositions comprise individual manganese (II), (III) and (IV) species. This means that the pretreatment composition comprises at least three different manganese species, which are different from each other, throughout the process. All three species are present simultaneously. In the context of the present invention, the terms "manganese (II), (III) and (IV)" denote manganese elements and/or ions having oxidation numbers +2, +3 and +4, respectively, in the corresponding compounds.

Preferred is a method according to the invention wherein the individual manganese (II), (III) and (IV) species are present in the pretreatment composition in a steady state during step (a).

The method of the present invention produces a unique, fine, sponge-like etched pattern/structure that allows the substrate to be sufficiently roughened without creating too deep or too large cavities (i.e., soft etching). Although deep and/or large cavities are often required to obtain a strong adhesion to the metal layer, investigation has shown that such deep/significant cavities tend to negatively impact the optical appearance of the final decorative layer (e.g. chrome layer), particularly in terms of brightness and uniformity. Such deep/pronounced cavities (undesirable in the context of the present invention) are typically obtained if the substrate is contacted with a composition comprising an appropriate amount of manganese (VII) species, in particular permanganate ions. In contrast, the fine sponge-like etched pattern/structure, while seemingly a disadvantage, is in fact a great advantage of the present invention. This is especially the case if the manufacturing quality of the substrates is different; this problem is sometimes observed for substrates containing butadiene moieties, preferably polybutadiene. Often such defects are caused by different manufacturing parameters during the casting process, often resulting in uneven material distribution or other manufacturing defects. Such defects are not necessarily visible from the beginning but tend to become apparent or at least prominent in the pretreatment step. However, if the pretreatment step shows such defects, the optical quality of the corresponding metallized substrate is deteriorated in many cases, especially at such areas of the substrate.

Surprisingly, the inventive method not only produces good results for high quality substrates, but also very acceptable results for substrates with manufacturing defects, i.e. lower manufacturing quality. In most cases, the optical appearance of the resulting metallized substrate is still very uniform due to less obvious manufacturing defects. The inventive method thus allows for metallization of substrates that would otherwise be discarded.

In the method of the invention, an electrical current is applied to the pretreatment composition such that the manganese (II) species is oxidized to a manganese (III) species, preferably continuously. Further procedural advantages are thereby obtained.

First, in the process of the present invention, no firmly adhering particulate manganese dioxide is formed in step (a), otherwise chemical reduction must be performed by contacting the substrate with a composition comprising a reducing agent. Instead, it is easily removed by simple rinsing, usually applied in any way (most preferably with water). Removal can be accomplished quickly and easily since it does not adhere strongly to the substrate (i.e., it is not incorporated into the substrate).

Second, the current may keep the individual manganese (II), (III) and (IV) species within a single and relatively constant concentration range, which would not be possible without the current. Furthermore, some manganese species, particularly manganese (III) species, are not present in the absence of an applied current. Thus, without wishing to be bound by any theory, the presence of individual manganese (II), (III) and (IV) species in the pretreatment composition caused by the current is critical to achieving the advantages described above. It is believed that the primary manganese species required to achieve good pretreatment results is the manganese (IV) species.

Furthermore, the electric current preferably breaks down the water that normally accumulates in the pretreatment composition, for example due to hygroscopic effects. Thus, the quality of the pretreatment composition remains stable (e.g., in terms of density).

Detailed Description

The method of the present invention generally comprises contacting with a specific pretreatment composition to obtain a particularly pretreated substrate.

Preferred is a method according to the invention wherein in step (a) the pretreatment composition is an etching composition for etching a nonmetallic substrate, preferably defined herein as a preferred nonmetallic substrate.

Step (A):

a nonmetallic substrate:

preferred is a method of the invention wherein the non-metallic substrate comprises, preferably is, a non-conductive substrate.

Preferred is a method according to the invention wherein the nonmetallic substrate comprises, preferably, a plastic substrate.

More preferred is a method of the invention wherein the nonmetallic substrate (and the nonconductive substrate, respectively) contains a butadiene moiety, preferably polybutadiene.

Also preferred is a method of the invention wherein the nonmetallic substrate (and the nonconductive substrate, respectively) contains nitrile moieties.

Also preferred is a method of the invention wherein the nonmetallic substrate (and the nonconductive substrate, respectively) contains a propylene-based moiety.

Also preferred is a method of the invention wherein the nonmetallic substrate (and the nonconductive substrate, respectively) includes styrene moieties.

Most preferred is a method of the invention wherein the nonmetallic substrate comprises, preferably, acrylonitrile-butadiene-styrene (ABS) and/or acrylonitrile-butadiene-styrene-polycarbonate (ABS-PC).

Pretreatment composition:

the pretreatment composition used in the method of the present invention comprises water. Preferably, the pretreatment composition comprises less than 50wt. -% water, preferably 45wt. -% or less, more preferably 40wt. -% or less, even more preferably 35wt. -% or less, still even more preferably 30wt. -% or less, most preferably 25wt. -% or less, based on the total weight of the pretreatment composition. Preferred is a method according to the invention wherein the pretreatment composition comprises water in an amount of 0 to 25wt. -%, preferably 0.1 to 21wt. -%, more preferably 1 to 18wt. -%, even more preferably 2 to 16wt. -%, still even more preferably 5 to 14wt. -%, most preferably 8 to 12wt. -%, based on the total weight of the pretreatment composition. Most preferably, water is the only solvent in the pretreatment composition.

In the method of the invention, the pretreatment composition comprises a specific manganese species. Other manganese species are less preferred, or most preferably avoided altogether.

Preferred is a method according to the invention wherein in step (a) the pretreatment composition is substantially free, preferably free, of manganese (VII) species, or only up to a total concentration of 100mg/L, preferably up to a total concentration of only 75mg/L, more preferably up to a total concentration of only 50mg/L, even more preferably up to a total concentration of only 35mg/L, most preferably up to a total concentration of only 20mg/L, even most preferably up to a total concentration of only 10mg/L, based on the total volume of the pretreatment composition and on elemental manganese. Self-experiments have shown that insignificant lower amounts (e.g. as impurities or due to unavoidable side reactions) of such manganese species are tolerable. However, preferred is a method of the invention wherein the pretreatment composition comprises manganese (VII) species at a concentration of 0mg/L to 10mg/L, based on the total volume of the pretreatment composition.

The manganese (VII) species, if present, is preferably formed in situ, preferably only, most preferably to a concentration range as defined above. This means that the manganese (VII) species is preferably not intentionally/deliberately added to the pretreatment composition.

Preferred is a method according to the invention wherein in step (a) the pretreatment composition is substantially free, preferably free, of permanganate ions, or only up to a total concentration of 100mg/L, preferably up to a total concentration of only 75mg/L, more preferably up to a total concentration of only 50mg/L, even more preferably up to a total concentration of only 35mg/L, most preferably up to a total concentration of only 20mg/L, even most preferably up to a total concentration of only 10mg/L, based on the total volume of the pretreatment composition and on elemental manganese. The same applies to the abovementioned description of the manganese (VII) species.

The permanganate ions, if present, are preferably (preferably only) formed in situ, most preferably to reach a concentration range as defined above. This means that the permanganate ions are preferably not intentionally/deliberately added to the pretreatment composition.

Preferred is a process according to the invention wherein the pretreatment composition is substantially free, preferably free, of methane sulphonic acid and salts thereof, preferably substantially free, preferably free, of C1 to C4 alkyl sulphonic acids and salts thereof, most preferably substantially free, preferably free, of C1 to C4 sulphonic acids and salts thereof. Such compounds appear to have a negative impact on the water balance in the corresponding pretreatment composition.

Preferred is a process according to the invention wherein the pretreatment composition is substantially free, preferably free, of bromide and iodide anions, preferably substantially free, preferably free, of chloride, bromide and iodide anions, most preferably substantially free, preferably free, of halide anions.

Preferred is a process according to the invention wherein the pretreatment composition is substantially free, preferably free, of trivalent and hexavalent chromium compounds, preferably substantially free, preferably free of any chromium containing compounds and ions.

Preferred is a method according to the invention wherein the pretreatment composition is substantially free, preferably free, of manganese (V) species, or only reaches a total concentration of 100mg/L, preferably only 75mg/L, more preferably only 50mg/L, even more preferably only 35mg/L, most preferably only 20mg/L, even most preferably only 10mg/L, based on the total volume of the pretreatment composition and based on elemental manganese. Most preferably, the manganese (V) species is undetectable, preferably by UV/VIS spectroscopy. Preferably, it is not intentionally/deliberately added to the pretreatment composition.

Preferred is a method according to the invention wherein the pretreatment composition is substantially free, preferably free, of manganese (VI) species, or only reaches a total concentration of 100mg/L, preferably only 75mg/L, more preferably only 50mg/L, even more preferably only 35mg/L, most preferably only 20mg/L, even most preferably only 10mg/L, based on the total volume of the pretreatment composition and based on elemental manganese. Most preferably, the manganese (VI) species is undetectable, preferably by UV/VIs spectroscopy. Preferably, it is not intentionally/deliberately added to the pretreatment composition.

As previously described, the pretreatment composition comprises individual manganese (II), (III) and (IV) species. Preferred is a method according to the invention wherein during step (a) the total amount of all manganese species in the pretreatment composition exceeds 5.0g/L, preferably 5.4g/L or more, even more preferably 5.8g/L or more, most preferably 6.0g/L or more based on the total volume of the pretreatment composition and on elemental manganese. The preferred maximum concentration is up to 7.5g/L, preferably up to 7.2g/L, more preferably up to 7.0g/L, even more preferably up to 6.8g/L, even more preferably up to 6.6g/L, most preferably up to 6.3g/L, based on the total volume of the pretreatment composition and based on elemental manganese.

Preferred is a method of the invention wherein the manganese (III) species is disproportionate to the manganese species comprising the manganese (IV) species in the pretreatment composition.

Preferred is a method according to the invention wherein the manganese (II) species comprises Mn (II) ions, preferably Mn (II) ions.

Preferred is a method according to the invention wherein during step (A) the total concentration of manganese (II) species in the pretreatment composition is in the range of 0.1g/L to 0.8g/L, preferably 0.15g/L to 0.7g/L, more preferably 0.2g/L to 0.6g/L, most preferably 0.25g/L to 0.5g/L, based on the total volume of the pretreatment composition and on elemental manganese. This preferably includes all manganese species as long as the oxidation number of the manganese element is +2.

One preferred source of the manganese (II) species is manganese (II) sulfate.

Preferred is a method according to the invention wherein the manganese (III) species comprises Mn (III) ions, preferably Mn (III) ions.

Preferred is a method according to the invention wherein during step (A) the total concentration of manganese (III) species in the pretreatment composition is in the range of 0.2g/L to 1.9g/L, preferably 0.3g/L to 1.5g/L, more preferably 0.4g/L to 1.2g/L, even more preferably 0.5g/L to 1.0g/L, most preferably 0.6g/L to 0.8g/L, based on the total volume of the pretreatment composition and elemental manganese.

Preferred is a method according to the invention wherein during step (a) the total concentration of manganese (III) species in the pretreatment composition is higher than the manganese (II) species. Preferably, this applies to concentrations in g/L based on elemental manganese, more preferably, on elemental manganese in these manganese species, based on the total volume of the pretreatment composition.

Preferred is a method of the invention wherein the manganese (IV) species comprises a colloidal manganese (IV) species, preferably a mixture of a colloidal manganese (IV) species and manganese (IV) ions.

Preferred is a method according to the invention wherein during step (A) the total concentration of manganese (IV) species in the pretreatment composition is in the range of 1.5g/L to 5.0g/L, preferably 1.8g/L to 4.5g/L, more preferably 2.0g/L to 4.0g/L, even more preferably 2.2g/L to 3.5g/L, most preferably 2.4g/L to 3.0g/L, based on elemental manganese, based on the total volume of the pretreatment composition.

Preferred is a method according to the invention wherein in the pretreatment composition more than 50wt. -% of the manganese (IV) species comprises colloidal manganese (IV) species, preferably 60wt. -% or more, more preferably 65wt. -% or more, most preferably 70wt. -% or more, based on the total weight of all manganese (IV) species and based on elemental manganese. Preferably, the colloidal manganese (IV) species comprises manganese dioxide.

In the pretreatment composition used in the method of the invention, the total concentration of manganese (IV) species is higher than the combined concentration of manganese (II) and (III) species. Preferably, this applies to the concentration in g/L based on the total volume of the pretreatment composition and based on the manganese element in each individual manganese species.

Preferred is a method according to the invention wherein during step (a) 55wt. -% or more of the pretreatment composition is a manganese (IV) species, preferably 59wt. -% or more, more preferably 63wt. -% or more, even more preferably 67wt. -% or more, most preferably 70wt. -% or more, based on the total weight of all manganese species and manganese elements.

Preferred is a process according to the invention wherein the pretreatment composition is acidic, preferably at a pH of 3.0 or less, more preferably 2.1 or less, even more preferably 1.5 or less, most preferably 1.0 or less, even most preferably 0.7 or less. Preferably, the strongly acidic condition is the result of the presence of an acid in the pretreatment composition.

Preferred is a process according to the invention wherein the pretreatment composition additionally comprises

(A-b) one, two or more (preferably two) acids, preferably mineral acids, most preferably at least a combination of sulfuric acid and phosphoric acid.

Preferred is a process according to the invention wherein the pretreatment composition comprises sulfuric acid in a total concentration of 10mol/L or less, preferably 9.6mol/L or less, more preferably 9.1mol/L or less, most preferably 8.6mol/L or less, based on the total volume of the pretreatment composition.

Preferred is a process according to the invention wherein the pretreatment composition comprises sulfuric acid in a total concentration of at least 3.0mol/L, preferably at least 3.5mol/L, more preferably at least 4.0mol/L, most preferably at least 4.5mol/L, based on the total volume of the pretreatment composition.

Preferred is a process according to the invention wherein the concentration of sulfuric acid in the pretreatment composition ranges from 3 to less than 10mol/L, preferably from 3.5 to 8mol/L, more preferably from 4 to 6mol/L, most preferably from 4.5 to 5.5mol/L, based on the total volume of the pretreatment composition.

Preferred is a process according to the invention wherein the pretreatment composition comprises at least a combination of sulfuric acid and phosphoric acid, wherein the concentration of phosphoric acid is higher than sulfuric acid, preferably the molar ratio of phosphoric acid to sulfuric acid is in the range of 1.1:1 to 3:1, more preferably 1.3:1 to 2.6:1, even more preferably 1.4:1 to 2.4:1, even more preferably 1.5:1 to 2.1:1, most preferably 1.6:1 to 2.0:1.

In the context of the present invention, it is most preferred that the concentration of phosphoric acid is higher than that of sulfuric acid. Typically, sulfuric acid is admixed with relatively high amounts of water due to hygroscopic effects. This results in an undesirable dilution of the pretreatment composition. If the concentration of sulfuric acid is reduced as much as possible, this dilution is also reduced. Self-experiments have shown that the concentration and molar ratio of sulfuric acid as defined above results in an excellent balance between, on the one hand, accumulation of water and, on the other hand, decomposition of water by means of electric current. This allows the pretreatment composition to remain in a stable state (stable water balance).

Preferred is a method according to the invention wherein the absorbance of the pretreatment composition exceeds 1.0, preferably in the range of 1.1 to 2.1, more preferably 1.2 to 2.0, most preferably 1.3 to 1.7, with reference to a wavelength of 400nm and a path length of preferably 1 cm. If the absorbance is significantly below 1.0, an undesirably low viscosity (e.g. < 0.5N/cm) is typically observed between the nonmetallic substrate and the metallic layer applied in step (C). In contrast, if the absorbance is higher than 1.0, particularly within the above-mentioned preferred range, good adhesion (e.g., > 1.0N/cm) is generally even observed. This parameter is a preferred quality parameter for assessing whether three manganese species are properly present in the pretreatment composition.

Preferably, the absorbance (also referred to as extinction ratio) is determined by UV/VIS spectroscopy (Beer-Lambert law) with a path length of 1cm at 400 nm.

(a-c) one or more species of additional transition metal ions other than manganese.

Preferred is a process according to the invention wherein the total concentration of one or more additional transition metal ions other than manganese in the pretreatment composition ranges from 1mmol/L to 50mmol/L, preferably from 2mmol/L to 40mmol/L, more preferably from 3mmol/L to 30mmol/L, even more preferably from 4mmol/L to 20mmol/L, most preferably from 5mmol/L to 15mmol/L, based on the total volume of the pretreatment composition.

Preferred is a method according to the invention wherein in the pretreatment composition one or more additional transition metal ions other than manganese comprise silver ions, preferably in a total concentration in the range of 4 to 25mmol/L, preferably 6 to 20mmol/L, more preferably 8 to 17mmol/L, most preferably 10 to 14mmol/L, based on the total volume of the pretreatment composition. Very preferably, the silver ion is the only further transition metal ion. In the context of the present invention, the total concentration of silver ions described above includes any number of oxidation of silver ions. Since silver ions are preferably present, halide ions, particularly chloride ions, are avoided to prevent precipitation.

Preferred is a method of the invention wherein the oxidation number of silver ions is +1, most preferred is silver ions added to the pretreatment composition.

(A-d) one or more wetting agents, preferably fluorinated wetting agents.

Preferred is a process according to the invention wherein the total concentration of the one or more wetting agents (preferably fluorinated wetting agents) in the pretreatment composition is in the range of 0.001g/L to 1.0g/L, preferably in the range of 0.005g/L to 0.7g/L, more preferably in the range of 0.01g/L to 0.5g/L, even more preferably in the range of 0.02g/L to 0.3g/L, most preferably in the range of 0.03g/L to 0.15g/L, based on the total volume of the pretreatment composition. Preferably, the fluorinated wetting agent is partially or fully fluorinated, or a mixture thereof (if, for example, more than one wetting agent is present).

(A-e) peroxomonosulfate anions and/or peroxodisulfate anions, preferably in a total concentration in the range of from 0.01g/L to 10.0g/L, preferably from 0.05g/L to 7.0g/L, more preferably from 0.1g/L to 4.0g/L, even more preferably from 0.2g/L to 2.0g/L, most preferably from 0.1g/L to 0.5g/L, based on the total volume of the pretreatment composition.

In some rare cases, it is preferred that a method of the invention wherein the pretreatment composition additionally comprises

(A-f) peroxymonophosphate anions and/or peroxydiphosphate anions, preferably in a total concentration in the range of from 0.01g/L to 10.0g/L, preferably from 0.05g/L to 9.0g/L, more preferably from 0.07g/L to 8.0g/L, even more preferably from 0.09g/L to 7.0g/L, most preferably from 0.1g/L to 5.0g/L, based on the total volume of the pretreatment composition.

The (A-g) nitrate anions are preferably present in a total concentration in the range of from 0.01g/L to 20.0g/L, preferably from 0.05g/L to 17.0g/L, more preferably from 0.1g/L to 13.0g/L, even more preferably from 0.25g/L to 9.0g/L, most preferably from 0.5g/L to 5.0g/L, based on the total volume of the pretreatment composition.

Preferably, the source of nitrate anions is silver nitrate. Most preferably, the total concentration of nitrate anions corresponds to the total concentration of silver ions. Most preferably, the only source of silver ions and nitrate anions is silver nitrate.

Preferably, the above components (A-c), (A-e), (A-f) and (A-g) support electrochemical reactions in the pretreatment composition.

Preferred is a process according to the invention wherein the pretreatment composition has a density of 1.50g/cm with reference to a temperature of 25 DEG C ³ To 1.90g/cm ³ Preferably 1.55g/cm ³ To 1.80g/cm ³ More preferably 1.60g/cm ³ To 1.70g/cm ³ Most preferably 1.61g/cm ³ To 1.68g/cm ³ Within the range. Such a density range indicates that a suitable water balance is provided.

Contact:

preferred is a process according to the invention wherein in step (A) the polybutadiene is mainly pretreated, preferably etched, if the substrate comprises acrylonitrile-butadiene-styrene (ABS) and/or acrylonitrile-butadiene-styrene-polycarbonate (ABS-PC), preferably acrylonitrile-butadiene-styrene (ABS) and/or acrylonitrile-butadiene-styrene-polycarbonate (ABS-PC), most preferably the polybutadiene is more pretreated, preferably etched, than the acrylonitrile styrene.

More preferred is a method according to the invention wherein the substrate and the pretreated substrate, respectively, are not otherwise contacted with a composition comprising permanganate ions, preferably are not otherwise contacted with a composition comprising manganese (VII) species.

More preferred is a method of the invention wherein the substrate and the pre-treated substrate, respectively, are not contacted with any composition comprising permanganate ions, the total concentration of said ions being 2g/L or more, preferably 1g/L or more, even more preferably 500mg/L or more, still more preferably 250mg/L or more, most preferably 150mg/L or more, based on the total volume of the composition.

Even more preferred is a method according to the invention wherein the substrate and the pretreated substrate, respectively, are not contacted with any composition comprising manganese (VII) species. This is most preferred if the pretreatment composition used in the process of the invention is substantially free, preferably free, of manganese (VII) species.

Preferred is a process according to the invention wherein during step (A) substantially no, preferably no manganese dioxide (MnO) ₂ ) Is incorporated onto the pretreated substrate. Thus, in the present inventionIn the method, no step is required (and therefore applied) to reduce manganese dioxide on the pretreated substrate; namely, mnO is dissolved by chemical reduction by a reducing agent ₂ . Thus, preferably, the pretreated substrate obtained after step (a) is not contacted with a corresponding composition comprising a reducing agent.

In contrast, preferred is a method of the invention wherein manganese dioxide adsorbed on the pretreated substrate after step (a) or before step (B), preferably if present, is removed by rinsing, preferably with water, more preferably with water free of a reducing agent capable of chemically reducing manganese dioxide.

Preferred is a method according to the invention wherein during step (a) or prior to step (B) the pretreated substrate is not contacted with a composition comprising a reducing agent capable of chemically reducing manganese dioxide, preferably is not contacted with a composition comprising any reducing agent.

Such steps are not required due to the specific composition of the pretreatment composition and its manner of use in the method of the invention.

Preferred is a method according to the invention wherein in step (a) the temperature of the pretreatment composition is in the range of 15 ℃ to 60 ℃, preferably 20 ℃ to 55 ℃, more preferably 27 ℃ to 50 ℃, even more preferably 34 ℃ to 46 ℃, most preferably 38 ℃ to 43 ℃.

Preference is given to a process according to the invention in which step (A) is carried out for a time in the range from 1 minute to 25 minutes, preferably from 5 minutes to 20 minutes, most preferably from 10 minutes to 18 minutes.

Current flow:

preferred is a process according to the invention wherein the current is applied continuously during step (a).

Preferred is a process according to the invention wherein manganese (III) species are continuously formed by means of an electric current during step (a).

Preferred is a process according to the invention in which the anodic current density of the current is 0.1A/dm ² To 20A/dm ² Preferably 0.8A/dm ² To 15A/dm ² More preferably 1.5A/dm ² To 10A/dm ² Most preferably 2.1A/dm ² To 5.0A/dm ² Within the range.

Preferred is a method according to the invention wherein during step (A) the pretreatment composition is exposed to a current load in the range of 0.5Ah/L to 100Ah/L, preferably 1.0Ah/L to 70Ah/L, more preferably 2.0Ah/L to 50Ah/L, most preferably 4.0Ah/L to 30Ah/L, based on the total volume of the pretreatment composition.

Pretreatment chamber:

preferred is a method according to the invention wherein step (a) is performed in a pretreatment chamber comprising at least one cathode and at least one anode, preferably comprising at least one cathode, at least one anode and at least one membrane, such that the manganese (II) species is oxidized to the manganese (III) species in the pretreatment chamber.

Alternatively, but more preferably, a method according to the invention is carried out wherein step (a) is carried out in a pretreatment chamber in fluid connection with an oxidation chamber comprising at least one cathode and at least one anode, preferably comprising at least one cathode, at least one anode and at least one membrane, such that the manganese (II) species is oxidized to the manganese (III) species in the oxidation chamber. In such preferred methods of the invention, the pretreatment chamber preferably does not contain a cathode and an anode. In such cases, the pretreatment composition is preferably circulated continuously or semi-continuously between the pretreatment chamber and the oxidation chamber.

Preferred is a process according to the invention wherein the individual manganese (II), (III) and (IV) species migrate (preferably circulate) between the pretreatment chamber and the oxidation chamber.

Preferred is a method according to the invention wherein an electric current is applied to the oxidation chamber.

Preferred is a method of the invention wherein at least one anode comprises a mixed metal anode or a graphite anode.

Preferred mixed metal anodes comprise at least two of lead, tin, silver, titanium and platinum.

More preferred mixed metal anodes comprise at least lead and tin, even more preferably at least lead, tin and silver. Self-experiments have shown that when using anodes comprising lead, tin and silver, the preparation time of the corresponding pretreatment composition is significantly shorter than when using anodes comprising lead and tin but no silver.

Most preferred are mixed metal anodes comprising lead, 0.1 to 3.0wt. -% silver, and 1.0 to 10.0wt. -% tin, based on the total weight of the mixed metal anode. Preferably, the balance to 100wt. -% is lead.

Preferred is a method according to the invention wherein the mixed-metal anode comprises 0.2 to 2.0wt. -% silver, based on the total weight of the mixed-metal anode.

Preferred is a method according to the invention wherein at least one cathode is a mixed metal cathode or a graphite cathode, preferably a mixed metal cathode, even more preferably comprising at least lead and tin, most preferably a mixed metal cathode comprising at least lead and 1.0wt. -% to 10.0wt. -% tin, based on the total weight of the at least one cathode.

Preferred is a method of the invention wherein at least one anode has a total anode surface and at least one cathode has a total cathode surface, wherein the ratio of total anode surface to total cathode surface is 2:1 or more, preferably 3:1 or more, more preferably 4:1 or more, most preferably 5:1 or more.

Step (B):

in step (B) of the method of the invention, the pretreated substrate is contacted with an activating composition. Step (a) comprises all steps performed before step (B), preferably including rinsing and other optional steps performed before and/or after step (a), e.g. expansion and/or conditioning steps.

In some cases, particularly preferred is a process of the invention comprising, prior to step (B), but after contact with the pretreatment composition, performing a conditioning step with a conditioning composition, i.e. contacting with a conditioning composition. Self-experiments have shown that such a conditioning step greatly increases (and thereby improves) the adsorption of palladium in step (B). In other words, after step (B) is completed, the total amount of palladium adsorbed and adhered, respectively, on the nonmetallic substrate is significantly increased as compared to the inventive method without such conditioning step. In some cases, the total amount of adsorption, i.e. the respective adhesion, is sufficient for the subsequent so-called direct metallization. In general, such conditioning steps reduce the amount of palladium wasted due to the increase in adsorption (and thus increased efficiency) in step (B).

Preferably, the nonmetallic substrate is rinsed in a rinsing step, preferably at least once with water, after contact with the conditioning composition.

Preferred is a method of the present invention wherein the conditioning composition is alkaline, preferably at a pH of 9 to 14, more preferably 10 to 13.5, even more preferably 11 to 13, most preferably 11.5 to 12.5.

Preferred is a method of the invention wherein the conditioning composition comprises an amine compound, preferably a diamine compound.

More preferred is a method of the invention wherein the conditioning composition comprises at least two amine compounds, preferably at least two diamine compounds.

Preferred amine compounds and diamine compounds each comprise an alkyl moiety, preferably an alkyl moiety having from 2 to 12 carbon atoms, preferably from 2 to 10 carbon atoms, more preferably from 2 to 8 carbon atoms, most preferably from 2 to 6 carbon atoms. Most preferably, if related to diamines, this means alkylene, i.e. a divalent moiety.

Very preferred diamine compounds comprise hexamethylenediamine, i.e. hexamethylenediamine (most preferably hexane-1, 6-diamine) and/or ethylenediamine, i.e. ethylenediamine (most preferably ethane-1, 2-diamine).

Preferred is a process according to the invention wherein the conditioning step is carried out for 0.1 to 15 minutes, preferably 0.2 to 11 minutes, more preferably 0.3 to 8 minutes, even more preferably 0.4 to 5 minutes, most preferably 0.5 to 2.5 minutes.

Preferred is a method according to the invention wherein in the conditioning step the temperature of the conditioning composition is in the range 25 ℃ to 50 ℃, preferably 28 ℃ to 46 ℃, more preferably 30 ℃ to 42 ℃, even more preferably 32 ℃ to 39 ℃, most preferably 34 ℃ to 37 ℃.

In the process of the present invention, it is preferred that step (B) is a step separate and independent from step (A). In other words, the pretreatment composition used in step (a) is not the activating composition used in step (B).

Preferred is a process according to the invention wherein in step (B) the activating composition comprises palladium, preferably dissolved palladium ions or colloidal palladium, most preferably colloidal palladium. Preferably, the colloidal palladium comprises tin.

Preferred is a process according to the invention wherein in step (B) the activating composition comprises palladium in a total concentration in the range of 20mg/L to 200mg/L, preferably in the range of 40mg/L to 150mg/L, even more preferably in the range of 50mg/L to 110mg/L, most preferably in the range of 55mg/L to 80mg/L, based on the total volume of the activating composition. Preferably, this total concentration includes dissolved palladium ions and colloidal palladium. The above concentrations are based on palladium element.

Preferred is a process according to the invention wherein in step (B) the temperature of the activating composition is in the range 25 ℃ to 70 ℃, preferably 30 ℃ to 60 ℃, even more preferably 36 ℃ to 50 ℃, most preferably 39 ℃ to 46 ℃.

Preferred is a process according to the invention wherein in step (B) the contacting is carried out for a time in the range of 1 to 15 minutes, preferably 2 to 12 minutes, even more preferably 3 to 9 minutes, most preferably 4 to 7 minutes.

Preferably a process according to the invention, wherein step (B) comprises the steps of

(B-1) contacting the activated substrate with an accelerator composition comprising

No reducing agent, but at least one complexing agent for tin ions, if in step (B) the activating composition comprises colloidal palladium, or

-a reducing agent for reducing palladium ions to metallic palladium, if in step (B) the activating composition comprises palladium ions but no colloidal palladium.

Preferred is a process according to the invention wherein in step (B-1) the accelerator composition does not comprise a reducing agent but comprises at least one complexing agent for tin ions and is acidic, preferably additionally comprises sulfuric acid.

In the context of the present invention, step (B-1) as defined above is carried out after contacting the pretreated substrate with the activating composition, so that an activated substrate is obtained.

Step (C):

in step (C) of the method of the invention, the activated substrate is metallized. Preferred is a process according to the invention wherein step (C) comprises contacting with at least one metallizing composition comprising nickel ions, preferably with at least two different metallizing compositions, each comprising nickel ions, most preferably prior to contacting with the metallizing composition comprising copper ions. Most preferably, at least one, preferably at least two, metallizing compositions are used for depositing nickel and/or nickel alloy metal layers, respectively.

In accordance therewith, a process according to the invention is preferred, wherein step (C) comprises the following steps

(C-1) contacting the activated substrate with a first metallization composition for electroless plating to obtain a metallized substrate having a first nickel/nickel alloy metal layer, wherein the first metallization composition comprises nickel ions and a reducing agent for the nickel ions.

Preferred is a method according to the invention wherein in step (C-1) the first metallization composition is alkaline, preferably having a pH in the range of 8.0 to 11.0, preferably 8.2 to 10.2, more preferably 8.4 to 9.3, most preferably 8.6 to 9.0.

Preferred is a method according to the invention wherein in step (C-1) the temperature of the first metallization composition is in the range of 18 ℃ to 60 ℃, preferably 20 ℃ to 55 ℃, to more preferably 23 ℃ to 50 ℃, most preferably 26 ℃ to 45 ℃.

Preferred is a process according to the invention, wherein step (C) comprises the following steps after step (C-1)

(C-2) contacting the metallized substrate having the first nickel/nickel alloy metal layer with a second metallization composition for electrolytic plating to obtain a metallized substrate having a second nickel/nickel alloy metal layer, wherein the second metallization composition comprises nickel ions and is preferably substantially free, preferably free of a reducing agent for nickel ions.

Preferred is a process according to the invention wherein in step (C-2) the second metallization composition is acidic, preferably having a pH in the range of 1.0 to 5.0, preferably 2.0 to 4.5, more preferably 2.8 to 4.0, most preferably 3.3 to 3.7.

Preferred is a method according to the invention wherein in step (C-2) the temperature of the second metallization composition is in the range of 25 ℃ to 70 ℃, preferably 35 ℃ to 65 ℃, even more preferably 45 ℃ to 61 ℃, most preferably 52 ℃ to 58 ℃.

Preference is given to a process according to the invention in which in step (C-2) the contacting is carried out for a time in the range from 1 minute to 10 minutes, preferably from 2 minutes to 8 minutes, most preferably from 2.5 minutes to 5.5 minutes.

Preference is given to a process according to the invention in which in step (C-2) an electric current is applied, preferably at 0.3A/dm ² To 10.0A/dm ² Preferably 0.5A/dm ² To 8.0A/dm ² More preferably 0.8A/dm ² To 6.0A/dm ² Even more preferably 1.0A/dm ² To 4.0A/dm ² Most preferably 1.3A/dm ² To 2.5A/dm ² Within the range.

Preferred is a process according to the invention wherein in step (C-2) the second metallization composition comprises chloride ions and/or (preferably and) boric acid.

Preferred is a process according to the invention wherein in step (C-2) the second metallization composition is a Watt (Watts) nickel composition. Thus, preferred is a process according to the invention wherein in step (C-2) the second metallization composition comprises chloride ions, sulfate ions and boric acid.

Although clearly less preferred, another process according to the invention is preferred, wherein step (C) comprises the following step after step (C-1)

(C-2) contacting the metallized substrate having the first nickel/nickel alloy metal layer with a second metallization composition to obtain a metallized substrate having a copper/copper alloy metal layer on the first nickel/nickel alloy metal layer, wherein the second metallization composition comprises copper ions and is preferably an immersed copper metallization composition.

However, as shown in the examples below, in this alternative process, undesirable foaming is observed in some cases.

Preferably a process according to the invention wherein step (C) follows step (C-2), most preferably if (C-2) involves nickel, comprises the steps of

(C-3) contacting the metallized substrate having the second nickel/nickel alloy metal layer with a third metallization composition to obtain a metallized substrate having a copper/copper alloy metal layer, wherein the third metallization composition comprises copper ions.

Preferred is a method according to the invention wherein in step (C) at least one of the one or more metallizing compositions comprises trivalent chromium ions such that a chromium or chromium alloy metal layer is deposited, respectively. Most preferably, the chromium or chromium alloy metal layers are respectively the outermost metal layers. Thus, most preferably, the method of the present invention is used for the metallization of nonmetallic substrates, wherein the metallization comprises a chromium deposit, preferably a decorative chromium deposit.

Particularly preferred is a process according to the invention wherein step (C) comprises a further step after step (C-3) as follows

(C-x) contacting the metallized substrate obtained after the step preceding step (C-x) with a further metallization composition to obtain a metallized substrate having a chromium/chromium alloy metal layer, wherein the further metallization composition comprises trivalent chromium ions.

The advantages attendant with the present invention are generally observed and recognized on chromium/chromium alloy layers.

The invention also relates to a specific pretreatment composition comprising

(A-a) Mn (II) ions, mn (III) ions and colloidal manganese (IV) species,

(A-b) one, two or more acids,

(A-c) silver ions,

wherein the pretreatment composition

-a density of 1.50g/cm with reference to a temperature of 25 DEG C ³ To 1.90g/cm ³ Within the range of

With reference to a wavelength of 400nm and a path length of preferably 1cm, the absorbance is in the range 1.1 to 2.1,

provided that the pretreatment composition

Substantially free, preferably free, of methanesulfonic acid, salts thereof and chloride ions,

substantially free, preferably free, of permanganate ions, or comprising permanganate ions up to a total concentration of only 100mg/L, preferably up to a total concentration of only 75mg/L, more preferably up to a total concentration of only 50mg/L, even more preferably up to a total concentration of only 35mg/L, most preferably up to a total concentration of only 20mg/L, even most preferably up to a total concentration of only 10mg/L, based on the total volume of the pretreatment composition and on elemental manganese.

The foregoing applies mutatis mutandis to the pretreatment composition of the present invention (if technically applicable) in relation to the process of the present invention, in particular in relation to the pretreatment composition used in the process of the present invention.

Examples

The invention will now be illustrated with reference to the following non-limiting examples.

The following method of metallizing a nonmetallic substrate was repeated for at least 3 months, with the parameters described below.

In an oxidation chamber containing a total of 6 tin/lead/silver anodes, 12 lead/tin (97 wt.%/3 wt.%) anodes and 9 tin/lead cathodes, the corresponding pretreatment composition was prepared as follows, wherein the ratio of total cathode surface to total anode surface was about 1:2:

first, a mixture of sulfuric acid and phosphoric acid is added to the chamber. Manganese (II) sulfate and silver nitrate were added and dissolved in the acid mixture so that the concentration of Mn (II) ions (i.e., manganese (II) species) exceeded 5g/L, but was below 6g/L. The silver concentration was about 12mmol/L.

Next, 1.2A/dm was applied ² To 1.5A/dm ² To oxidize Mn (II) ions to Mn (III) species. After 48 hours, pretreatmentThe absorbance of the composition at 400nm reached about 1.0. Absorbance was measured by UV/VIS spectroscopy, path length was 1cm.

Third, additional amounts of manganese sulfate are added at intervals under the application of an electric current and dissolved such that eventually after about 96 hours the absorbance at 400nm reaches more than 1.2. The density of the pretreatment composition was ultimately about 1.65g/L.

The pretreatment composition thus obtained used in the process of the invention does not contain methane sulphonic acid and does not contain intentionally added chromium-containing compounds/ions; in particular free of hexavalent chromium compounds. Furthermore, the pretreatment composition is free of chloride ions and free of intentionally added permanganate compounds/ions.

The oxidation chamber is fluidly connected to the pretreatment chamber (tank volume of about 5400 liters) to allow for continuous circulation of the pretreatment composition between the pretreatment chamber and the oxidation chamber. No anode and no cathode are installed in the pretreatment chamber.

In step (A) of the process of the invention, various nonmetallic plastic substrates (ABS or ABS-PC) are used, the surface size of which is 0.1dm2 to 10dm ² Within the scope, the manufacturing quality is the same). The substrate was cleaned with Uniclean 151 (attotech) and then air dried before being contacted with the pretreatment composition prepared in the pretreatment chamber.

TABLE 1 composition and pretreatment parameters during step (A)

* The representation is: determination by UV/VIS Spectroscopy

The concentration of manganese species is in g/L based on the total volume of the pretreatment composition and is based on elemental manganese.

In step (A), 1.2-1.5A/dm ² Is continuously applied to the oxidation chamberPretreatment composition.

It is notable that all substrates were contacted with the manganese species only in step (a) with the pretreatment composition defined in table 1 throughout the process. No additional contact is made with other manganese species containing compositions. Thus, step (a) is a one-step contact with the manganese species and is also the only step in the overall process that is contacted with the manganese species. This is a general and important feature of the overall process of the present invention.

After step (a), the pretreated substrate obtained an etched pattern, showing an exceptionally fine sponge-like structure after removal of polybutadiene spheres contained on the ABS and ABS-PC substrate surfaces, respectively. Self analysis confirmed that in the substrate, predominantly polybutadiene structures were etched, with acrylonitrile styrene of the substrate remaining intact. Thus, after step (a) a very fine-porous surface is obtained, which is etched to a significantly less strong extent than a substrate in contact with, for example, permanganate ions, but still provides sufficient adhesion. Thus, it is an excellent balance obtained between etching and adhesion.

Before step (B), rinsing with water. If there are any manganese dioxide particles on the substrate, it only needs to be rinsed off with water, since no firm adhesion of manganese dioxide is observed.

In step (B), the pretreated substrate is contacted with an activating composition comprising colloidal palladium (about 55mg/L to 80mg/L Pd at 42 ℃ C.) for 5 minutes.

In addition, step (B) comprises step (B-1) wherein the pretreated substrate is contacted with an acidic accelerator composition comprising at least one complexing agent for tin ions to modify the activated substrate, because in step (B) the activating composition comprises colloidal palladium.

Before step (C), rinsing with water.

In step (C), the activated substrate is contacted with more than one metallization composition to obtain a metallized substrate.

First, step (C) comprises step (C-1) wherein the activated substrate is contacted with an alkaline (pH of about 8.6 to 9.0) first metallization composition (temperature of about 26 ℃ C. To 45 ℃ C.; contact time of about 10 minutes) to effect electroless nickel plating. The first metallization composition comprises about 3.5g/L nickel ions and about 15g/L hypophosphite ions as a reducing agent for the nickel ions to obtain a metallized substrate having a first nickel alloy metal layer.

Second, step (C) includes step (C-2) after step (C-1), wherein the metallized substrate having the first nickel alloy metal layer is reacted with an acidic second metallization composition (Watt nickel composition) comprising nickel sulfate, nickel chloride and boric acid (pH of about 3.3 to 3.7; temperature of 55 ℃ C., current density of about 1.5A/dm) ² ) The contact is for about 2.5 to 5 minutes. Thus, step (C-2) is the electrolytic deposition of nickel.

Thereafter, the metallized substrate with the second nickel metal layer is rinsed with water.

Thereafter, in step (C-3), the respective substrate is contacted with a third metallization composition (acidic pH) to obtain a metallized substrate having a copper layer with a layer thickness exceeding 30 μm (contact time of about 45 minutes, 32.5 ℃,40g/L copper ions).

Thereafter, a further metallization step is performed in preparation for chromium deposition.

In the final metallization step (C-x), the respective substrate is contacted with a further metallization composition comprising 15g/L to 30g/L trivalent chromium and boric acid (acidic pH,25 ℃ to 60 ℃) to obtain a metallized substrate with a chromium layer.

Finally, the optical quality of the chromium layer was evaluated by analyzing the coverage and optical defects. As a result, no haze and other optical defects were observed. In particular, the chromium layer shows a very uniform optical distribution.

For adhesion testing, the substrate obtained after contact with the third metallization composition (i.e., plated with copper) was subjected to adhesion testing. Typically, the adhesion to ABS is higher than 1.0N/mm, and the adhesion to ABS-PC is in the range of 0.5 to 0.8N/mm.

The inventive process shows significantly higher adhesion (at least 10%) and furthermore reduces the tendency to form blisters compared to the comparative examples where copper is deposited instead of nickel in steps (C-1) and/or (C-2). This is particularly observed for substrates where the copper layer is deposited by immersion plating in step (C-2).

Furthermore, in comparison with the comparative examples using permanganate in the corresponding etching composition (as described for example in WO 2018/095998 A1), the method of the invention essentially comprises a single-step pretreatment procedure, which greatly reduces the time of the whole pretreatment procedure, since no contact with a composition comprising a reducing agent and/or no second contact step with a second manganese species or a further manganese species is required.

As a result of the present invention, the degradation of the acrylonitrile-styrene substrate of the substrate is significantly reduced, producing a much less aggressive etching result. This is important. Experiments with samples of lower manufacturing quality show that the etching results obtained with the method of the invention are sufficiently uniform and still result in a very acceptable optical quality. Surprisingly, even substrates of significantly lower quality show a very uniform metallization in self-experiments, since defects of the substrate are less pronounced in the pretreatment step compared to other known pretreatment methods, in particular in the case of inclusion of permanganate ions.

This benefit is most preferably applicable to substrates containing polybutadiene studied in self experiments.

Claims

1. A method of metallizing a nonmetallic substrate, the method comprising the steps of

wherein the pretreatment composition comprises

(A-a) individual manganese (II), (III) and (IV) species,

provided that it is

2. The method according to claim 1, wherein in step (a) the pretreatment composition is substantially free, preferably free of permanganate ions, or only reaches a total concentration of 100mg/L, preferably only a total concentration of 75mg/L, more preferably only a total concentration of 50mg/L, even more preferably only a total concentration of 35mg/L, most preferably only a total concentration of 20mg/L, even most preferably only a total concentration of 10mg/L, based on the total volume of the pretreatment composition and based on elemental manganese.

3. The method of claim 1 or 2, wherein in the pretreatment composition, manganese (III) species are disproportionate to manganese species comprising manganese (IV) species.

4. A method according to any one of claims 1 to 3, wherein the anodic current density of the current is at 0.1A/dm ² To 20A/dm ² Preferably 0.8A/dm ² To 15A/dm ² More preferably 1.5A/dm ² To 10A/dm ² Most preferably 2.1A/dm ² To 5.0A/dm ² Within the range.

5. The method of any one of claims 1 to 4, wherein during step (a) or prior to step (B), the pretreated substrate is not contacted with a composition comprising a reducing agent capable of chemically reducing manganese dioxide, preferably is not contacted with a composition comprising any reducing agent.

6. The method according to any one of claims 1 to 5, wherein during step (a), the total amount of all manganese species in the pretreatment composition exceeds 5.0g/L, preferably 5.4g/L or more, even more preferably 5.8g/L or more, most preferably 6.0g/L or more, based on the total volume of the pretreatment composition and on elemental manganese.

7. The method of any one of claims 1 to 6, wherein the pretreatment composition further comprises (a-b) a combination of one, two or more acids, preferably inorganic acids, most preferably at least sulfuric acid and phosphoric acid.

8. The method of claim 7, wherein the pretreatment composition comprises at least a combination of sulfuric acid and phosphoric acid, wherein the concentration of phosphoric acid is higher than the sulfuric acid, preferably the molar ratio of phosphoric acid to sulfuric acid is in the range of 1.1:1 to 3:1, more preferably in the range of 1.3:1 to 2.6:1, even more preferably in the range of 1.4:1 to 2.4:1, even more preferably in the range of 1.5:1 to 2.1:1, most preferably in the range of 1.6:1 to 2.0:1.

9. The method according to any one of claims 1 to 8, wherein the absorbance of the pretreatment composition exceeds 1.0, preferably in the range of 1.1 to 2.1, more preferably 1.2 to 2.0, most preferably 1.3 to 1.7, with reference to a wavelength of 400nm and a path length of 1 cm.

10. The method of any one of claims 1 to 9, wherein the pretreatment composition further comprises (a-c) one or more additional transition metal ions other than manganese.

11. The method of any one of claims 1 to 10, wherein the pretreatment composition has a density of 1.50g/cm with reference to a temperature of 25 °c ³ To 1.90g/cm ³ Preferably 1.55g/cm ³ To 1.80g/cm ³ More preferably 1.60g/cm ³ To 1.70g/cm ³ Most preferably 1.61g/cm ³ To 1.68g/cm ³ Within the range.

12. The method of any one of claims 1 to 11, wherein step (C) comprises contacting with at least one metallizing composition comprising nickel ions, preferably with at least two different metallizing compositions, each comprising nickel ions, most preferably prior to contacting with the metallizing composition comprising copper ions.

13. The method of any one of claims 1 to 12, wherein step (C) comprises the steps of

14. The method of claim 13, wherein step (C) comprises the following steps after step (C-1)

(C-2) contacting the metallized substrate with the first nickel/nickel alloy metal layer with a second metallization composition for electrolytic plating to obtain a metallized substrate with a second nickel/nickel alloy metal layer, wherein the second metallization composition comprises nickel ions and is preferably substantially free, preferably free of a reducing agent for nickel ions.

15. A pretreatment composition comprising

(A-a) Mn (II) ions, mn (III) ions and colloidal manganese (IV) species,

(A-b) one, two or more acids,

(A-c) silver ions,

wherein the pretreatment composition

With reference to a wavelength of 400nm and a path length of 1cm, an absorbance in the range 1.1 to 2.1,

provided that the pretreatment composition