CZ164995A3 - Conversion phosphate coating composition substantially free of nickel and method of making the phosphate coating - Google Patents

Abstract

The nickel in conventional low zinc and nickel containing phosphate conversion coating compositions can be replaced by substantially smaller concentrations of cupric ions without losing the benefits of quality that motivated the addition of nickel to low zinc phosphating compositions originally; in fact, better alkaline resistance and paint adhesion can be achieved, along with a substantial cost reduction.

Description

BACKGROUND OF THE INVENTION The present invention relates to a composition and method for forming a conversion phosphate coating on active metal surfaces to increase corrosion resistance of these surfaces, either as a treatment or following conventional application of a conversion coating layer to form a base protective coating such as pickle. The composition of the present invention is well applicable to the treatment of any of a variety of metallic substrates, including steel and galvanized steel and aluminum and aluminum based alloys.

BACKGROUND OF THE INVENTION

A wide variety of conversion phosphate coating compositions have been described in the art. In general, they are considered to be of the highest quality in which zinc, nickel, and at least one other divalent metal such as manganese is present in the composition.

SUMMARY OF THE INVENTION

In the following description, with the exception of the working examples and the claims, and unless expressly stated to the contrary, it is to be understood that all figures relating to the amount of substances or reaction or use conditions are possible with the word about in the sense describes a broader field for the invention.

In general, an embodiment of the invention which lies within given numerical limits is preferred.

According to some studies, nickel has been included as a carcinogen and therefore, for health reasons, it is advisable to avoid it when used in metal finishes.

Nickel is also considered to be a serious pollutant, and at concentrations of 0.5 to 1.5 grams per liter (hereinafter abbreviated as g / l) in which it is commonly used, nickel contributes significantly to the cost of zinc phosphate conversion coating. means. It is an object of the present invention to minimize or eliminate the use of nickel without compromising the quality of the conversion coating obtained by conventional means comprising zinc, nickel and manganese.

The composition of the present invention is an aqueous liquid composition which preferably forms water as a base, and is more preferably comprised of water and:

(A) from 3 to 50, more preferably from 5 to 20, and even more preferably from 13 to g / l of dissolved phosphate ions;

(B) from 0.2 to 3, or with increasing preference in the order as set forth below, from 0.45 to 2.0, 0.57 to 1.24, 0.60 to 0.95, or 0.71 up to 0.87 g / l of dissolved zinc ions;

(C) from 1 to 200, or, with increasing preference, in the following order, from 20 to 100, 24 to 74, or 24 to 60 milligrams per liter (mg / L) of dissolved copper ions;

(D) an effective amount of a conventional nitrate ion exclusion accelerator;

(E) from 5 to 40, or with increasing preference, in the order given below, from 7 to 25, 13 to 24, 16 to 22, or 18 to 21 total acidity points; and (F) from - 1.0 to + 3.0, or with increasing preference, in the following order, from - 0.5 to + 1.5 or - 0.5 to + 1.0 points of free acid; for substrates other than aluminum and operating temperatures above 40 ° C, a range of 0.0 to 0.8 or more preferably 0.35 to 0.65 points of free acid is even more preferred; however, when the process is carried out at a temperature of less than 40 ° C, or when the substrate is aluminum, a preferred range from - 0.5 to 0.0 or more preferably - 0.5 to - 0.2 points of free acid is even more preferred; and optionally, (G) up to 2 g / L, preferably from 0.1 to 0.8 g / L, or even more preferably from 0.40 to 0.65 g / L of the total amount of Mn + ⁺ and Co + ⁺ ions ;

(H) up to 2 g / L, preferably from 0.5 to 1.0 or even more preferably from 0.70 to 0.80 g / L of Mg ²⁺ ions; and, optionally, (J) to 5.5, preferably 1.0 to 4.0, even more preferably from 1.5 to 4.0

2.5 g / l of free fluoride, measured on a fluoride-sensitive electrode, and optionally, (K) no more than 40, or, with increasing preference, no more than 20 or 11 g / l SO ₄ ions; and, optionally, (L) not more than 4.5, or, with increasing preference, in the following order, not more than 3.4, 2.0, 1.8, 1.3 or 1.0 g / L of NO 2; ions.

It is further understood that the specification of the components in ionic form also includes the presence of some counter-ions with opposite charge, if it is desired to achieve a neutral charge in the composition as a whole.

The free acid (total acid) and total acid (total acid) points are defined for use herein as the number of milliliters (here ml) of the 0.1N-NaOH solution needed to titrate 10 ml of the formulation sample to the endpoint titration with phenolphthalein (pH 9.0) for total acidity and end point titration with bromothymol blue (pH 3.8) for free acidity, except that if the composition has a pH greater than 3.8 initial, the free acidity points are defined as negative ml ml 0 1N of the strong acid solution needed to titrate 10 ml of the formulation sample to pH 3.8.

The method of the present invention indicates, at a minimum degree of contact of the treated metal surface with the composition of the present invention, the time required to form a detectable conversion coating on the metal surface. If desired, conventional methods of cleaning and / or activating the metal surface can be used prior to contact between the metal and the compositions of the present invention, and it is generally preferred that they be part of the method of the present invention. The method of the invention may also, and usually is done, include conventional steps following contact between the treated metal surface and the compositions of the invention. These subsequent steps may include, for example, rinsing with water, any conventional reactive after-treatment, eg with the substances disclosed in US patent application 4,963,596 or with chromate-containing solutions, and coating or other surface protection methods using external coatings using solids are used. substances based on organic compounds.

In another embodiment, the present invention provides a concentrated composition from which a working composition as defined above can only be prepared by diluting with water or diluting with water and adding an unstable accelerator such as nitrite ions.

The phosphate ions required for the compositions of the present invention are preferably PO 4 ions or other ions that are derivable from incompletely ionized orthophosphoric acid (H 2 PO 4). For any unionized phosphoric acid that may be present, it is desirable that a certain volume thereof coincide with a stoichiometric corresponding volume of PO 2 ions. Necessary phosphate ions can also be replaced by other free phosphoric acids such as metaphosphoric acid and condensed phosphoric acids such as pyrophosphoric acid and any anions that can be derived therefrom. It is preferred that the phosphate ions be derived from orthophosphoric acid and / or its neutral or acidic metal cation salts, as also specified above as part of the composition of the invention.

The zinc cations that are required as part of the compositions are preferably derived from neutral or acidic salts of zinc and orthophosphoric acid, which are formed in situ by dissolving zinc or zinc oxide in an acid-containing solution.

The copper cations that are required as part of the compositions of this invention may be derived from salts such as cuprous sulfate and / or cuprous nitrate, or may be obtained by dissolving copper oxide in a portion of the phosphoric acid used.

The accelerator component required as part of the composition of the present invention preferably comprises at least one of the following:

(i) from 0.01 to 0.2 nitrite ions, (ii) from 0.5 to 5 g / l (iii) from 0.05 to 2 g / l of m-nitrobenzenesulfonate ions, (iv) from 0.05 to 2 g / l of m-nitrobenzoate ions, (v) from 0.05 to 2 g / l of p-nitrophenol, and (vi) from 0.1 to 10, more preferably from 0.5 to 6, or even more preferably from 0 , 5 to 2.0 g / L, as measured by a stoichiometric equivalent of hydroxylamine, a compound capable of providing hydroxylamine in aqueous solution. Most preferably, the accelerator is hydroxylamine sulfate (hereinafter referred to as HAS) or the like that is capable of providing and storing hydroxylamine. The second most preferred accelerator is nitrite ions.

The acidity of the compositions of the invention is preferably derived from phosphoric, sulfuric and / or nitric acid.

Part or even all of the fluorine can be derived from complex fluoride ions such as fluoroborate (BF?), Fluorhafnat (HfF?), Fluorosilicate (SiF?), Fluorotitanate (TiF?), B2 oo fluorzirconate (ZrF?) And mixtures thereof ; more preferred are fluoroborate and fluorosilicate and mixtures thereof. However, simple fluorides such as alkali metal fluorides are also satisfactory sources of free fluorine.

Increasing preference is given respectively and independently of the compounds, the composition of the invention should not contain more than 0.5, 0.2, 0.10, 0.07, 0.03, 0.01, 0.005 or 0.001 g / l for each Ni @ ⁺ , each cation having a bond of three or more, chloride ions include complex chloride ions and chlorate ions. Independently, if the chloride ions are present in a sufficient amount that can be readily analytically determined, it is preferable that the ratio of the concentration in g / l of complex fluoride ions to the concentration in g / l of chloride ions is at least 8: 1, or more preferably ratio of at least 14: 1.

In the method of the invention, contact between the metal surface to be treated and the composition of the invention is effected by spraying, dipping or dipping or other conventional methods or combinations thereof. The temperature during contact between the metal to be treated and the composition of the invention is preferred with an increasing preference, respectively, in the range of 21 to 85, 25 to 55, or 31 to 44 ° C. The total contact time between the composition of the invention and the metal surface to be provided with the conversion coating is, with increasing preference, in the order of 5 seconds to 15 minutes (min), 15 seconds (sec) ) to 10 min, from 30 sec to 5 min, or from 90 sec to 120 sec. The delivered amount of phosphate coating substance is preferably, with increasing preference, in the range of from 1.1 to 5.4, from 1.6 to 4.3, or from 2.2 to 3.8 grams per square meter (hereinafter referred to as " uses the abbreviation g / m) of the treated surface. The weight percent copper in the formed coating is, with increasing preference, respectively, from 0.50 to 10, from 1.0 to 8.0, from 2.0 to 6.0, from 3.0 to 4.1.

The following examples illustrate the invention, and comparative examples. All of the following examples illustrate the invention in more detail, but do not limit the scope or content of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Examples of resources and comparative examples of Group I

These means, with the exception of one comparative example, show the use of an HAS accelerator. Specific formulations are listed in Table 1 below. In addition to Comparative Example 13, where the preparation is based on a commercially combined concentrate, these formulations are prepared in the following general manner:

Initially, an amount of water equal to three quarters of the volume of the desired composition is used and dissolved in this amount of zinc dihydrogen phosphate to obtain the desired zinc ion concentration in the final volume, then an amount of 75% aqueous orthophosphoric acid is added. to obtain the desired final concentration of phosphate ions in the final volume together with the previously added zinc dihydrogen phosphate. An appropriate amount of sodium fluoride is added to the solution thus prepared in any order to provide the desired fluorine content, sufficient HAS to obtain the desired hydroxylamine concentration and some sulfate, sodium sulfate pentahydrate to obtain the desired copper ion concentration and a portion of the sulfate ion concentration. obtaining a desired concentration of manganese ions and a suitable amount of magnesium hydroxide or magnesium nitrite to obtain a desired concentration of magnesium ions. Finally, the composition is treated by adding sodium hydroxide solution and additional water to obtain a product with a specified concentration of free acid (free acid) and total acid (total acidity).

Method Examples and Comparative Examples with Group I compositions

Cold rolled steel, galvanized steel and / or common aluminum alloy test parts used in automotive and factory tools and instruments shall be used, subject to the following test method steps:

(1) conventional alkaline cleaning for 120 sec at 43 ° C;

(2) rinsing with water at 38 ° C for 60 sec;

(3) a conventional colloidal titanium phosphate activator operates at 38 ° C for 30 sec;

(4) contacting one of Formulations 1 to 12 of Table 1 below for 120 sec at 35 ° C or 43 ° C;

(5) cold water rinsing at 20-25 ° C for 60 sec;

(6) treatment for 30 seconds with a commercial hexavalent or trivalent chrome formulation; and (7) rinsing with deionized water for 30 sec at 20-25 ° C rH

Table

Cu ²⁺ in mg / l O O 27 Mar: 26 52 09 / O O 00 CN 24 57 55 O Notes to Table 1 Concentration in g / l i n O OF 1.2 ** O 1.2 0.95 1.2 ^ 4 O 1.3 O 1 O ω 8.4 9.9 9.9 oo 00 r 8.8 00 9.2 9.2 8.8 9.0 9.2 - O + CS tn and O O O O O O 0.79 0.71 0.77 0.72 0.73 0.73 O + C and O 0.46 O 0.46 O 0.48 O 0.49 O 0.47 O 0.47 99Ό n -r O & ΙΖΊ υη ι / Ί in ΙΖΊ vn <5 + <N 0.94 C\ F-* O' 0.64 0.62 0.71 0.77 0.87 0.87 0.78 0.79 0.76 0.62 - loosely F" 0.53 0.46 8ΙΌ 0.48 0.51 0.49 810 9Γ0 9Γ0 OO O OO O OO O 0.40 ACC 09Ί O Ό 1.56 09 l O Ό 09 ‘I 1.60 00 MD 1.52 O MD 09Ί 0.12 Points fa 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 9Ό AND 0 61 19.0 0 61 18.5 18.5 19.0 18.5 19.3 19.5 20.5 00 19.0 Identi- fikač- her number - es cn IN) r- 00 σ \ O - cs «-Μ cn ^ 4

ΤΑ = total acidity; FA = free acidity; ACC = Accelerator. The accelerator is the titanium ions for the composition with Identification Number 13 and the HAS for others.

it also contains 1.3 g / l Ni and thus is Zn-Ni-Mn phosphatizing lazine.

Ό II

Means and Examples of Group II Method

These compositions were prepared in the same manner as for Group I except that sodium nitrite was used instead of HAS as an accelerator and as a copper source copper nitrite having a diameter of 2.5 molecules of water per copper ion. The compositions have the following composition:

Component g / 1 components in: Example 14 Example 15 Zn _{(NO3) 2} 4.74 3.6 75% by weight aqueous Η-PO, 3 4 12.4 20.4 Cu (NO _{3) second} 2 1/2 H ₂ 0 0.44 0.29 NaF 1.1 1.5 NaNO ₂ 0.12 0.11 Mn _{(NO3) 2} 2.3 - Total acidity - points 17.0 18 Free acidity - points - 0,3 0.4

In Example 14, phosphatization spraying at 33 ° C was used in a sequentially different sequence than in Group I above. In Example 15, phosphating immersion at 57 ° C is used in a sequentially different sequence than Group I above.

Industrial applicability

The use of the compositions and methods of the present invention for surface treatment of metal surfaces not only reduces costs and reduces contamination, but a particularly advantageous embodiment improves corrosion resistance, particularly in the case of alkaline corrosion, at lower temperatures than conventional Zn- Ni-Mn phosphate compositions, where the quality is several times better, also the adhesion of the conversion coatings is improved, the improvement being reflected both on the zinc-containing surfaces and on the galvanized galvanized steel surfaces.

Claims (3)

(1) surface cleaning; (1) surface cleaning; (1) surface cleaning; (1) surface cleaning; (1) surface cleaning; (1) surface cleaning; An aqueous liquid composition comprising a substantial proportion of water and: (A) from 3 to 50 g / L dissolved phosphate ions; (2) contacting the surface to be cleaned with an activating agent comprising colloidal titanium; (2) contacting the surface to be cleaned with an activating agent comprising colloidal titanium; (3) forming a phosphate coating on the cleaned and activated surface by the method of claim 9; and (4) applying a solid organic substance-based outer coating to the phosphate coating formed in step (3). 20. A method of forming a protective coating on a surface of a metal substrate which does not contain aluminum on its surface, said method comprising the steps of: (2) contacting the surface to be cleaned with an activating agent comprising the titanium collide; (3) forming a phosphate coating on the cleaned and activated surface by the method of claim 10; and (4) applying a solid organic substance-based outer coating to the phosphate coating formed in step (3). 19. A method of forming a protective coating on a surface of a metal substrate comprising aluminum on its surface, said method comprising the steps of: (2) contacting the surface to be cleaned with an activating agent comprising colloidal titanium; (3) forming a phosphate coating on the cleaned and activated surface by the method of claim 11; and (4) applying a solid organic substance-based outer coating to the phosphate coating formed in step (3). 18. A method of forming a protective coating on a surface of a metal substrate comprising aluminum on its surface, wherein the method comprises the steps of: (2) contacting the surface to be cleaned with an activating agent comprising colloidal titanium; (3) forming a phosphate coating on the cleaned and activated surface by the method of claim 12; and (4) applying a solid organic substance-based outer coating to the phosphate coating formed in step (3). 17. A method of forming a protective coating on a surface of a metal substrate which does not contain aluminum on its surface, the method comprising the steps of: (2) contacting the surface to be cleaned with an activating agent comprising colloidal titanium; (3) forming a phosphate coating on the cleaned and activated surface by the method of claim 14; and (4) applying a solid organic substance-based outer coating to the phosphate coating formed in step (3). 16. A method of forming a protective coating on a surface of a metal substrate, the method comprising the steps of: 2+ up to 0.65 g / l; or (ii) the concentration of Mg ions is from 0.70 to 2+ 2+ 0.80 g / L; or (iii) concentrations of both total Mn and Co 2+ ions and Mg ions are within the ranges already specified for the individual ions at (G) (i) and (ii); and (L) the concentration of NO 2 ions is not more than 1.3 g / L. 8. A process for forming a phosphate coating on a surface of a metal substrate which does not contain aluminum on the surface, characterized in that it comprises: contacting the surface of the substrate for between 90 and 120 sec at a temperature between 40 and 44 ° C with the composition of claim 7, wherein the added weight amount of the phosphate coating composition is in the range of 2, 2 to 3.8 g / m and the weight percent of the medium in the phosphate coating formed is from 3.0 to 4.1. 9. A method of forming a phosphate coating on a surface of a metal substrate which comprises partially aluminum on the surface of the substrate comprising contacting the surface of the substrate for a period of from 90 to 120 sec at a temperature of from 31 to 44 ° C with the composition. according to claim 6, wherein the amount by weight of the added phosphate coating composition is in the range of from 2.2 to 3.8 g / m and the weight percent of copper in the formed phosphate coating is in the range of from 3.0 to 4.1. 10. A process for forming a phosphate coating on a surface of a metal substrate which contains partially aluminum on the surface of the invention, comprising contacting the surface of the substrate for a period of from 30 sec to 5 min at a temperature of 25 to 55 ° C. The composition of claim 5, wherein the amount by weight of the added phosphate coating composition is in the range of 1.6 to 4.3 g / m and the weight percent of copper in the formed phosphate coating is in the range of 2.0 to 6.0. 11. A process for forming a phosphate coating on a surface of a metal substrate which is free of aluminum as a component, comprising contacting the surface of the substrate for a period of from 30 sec to 5 min at a temperature of from 40 to 55 ° C. with the composition of claim 4, wherein the amount by weight of added phosphate composition is in the range of from 1.6 to 4.3 g / m and the weight percent of copper in the formed phosphate coating is in the range of from 2.0 to 6.0 A method of forming a phosphate coating on a surface of a metal substrate, comprising contacting the surface of the substrate for a period of from 15 sec to 10 min at a temperature of from 25 to 55 ° C with the composition of claim 3, wherein the amount by weight the added phosphate composition is in the range of from 1.1 to 5.4 g / m and the weight percent copper in the formed phosphate coating is in the range of from 1.0 to 8.0. A method of forming a phosphate coating on a surface of a metal substrate, the method comprising contacting the surface of the substrate for a period of from 5 sec to 15 min at a temperature of from 21 to 85 ° C with the composition of claim 2, the added phosphate composition ranges from 1.1 to 5.4 g / m and the weight percent copper in the formed phosphate coating ranges from 0.50 to 10.0. 14. A process for forming a phosphate coating on a surface of a metal substrate, the method comprising contacting the surface of the substrate for a time in the range of 5 sec to 15 min at a temperature in the range of 21 to 85 ° C with the composition of claim 1, the added phosphate composition ranges from 1.1 to 5.4 g / m and the weight percent copper in the formed phosphate coating ranges from 0.50 to 10.0. 15. A method of forming a protective coating on a surface of a metal substrate, the method comprising the steps of: 2+ 2+ (G) (i) the concentration of total Mn and Co ions is from 0.40 2+ 0.40 to 0.65 g / L; or (ii) the concentration of Mg ions is from 0.70 2+ 2+ to 0.80 g / L; or (iii) the concentrations of either the total Mn and Co ions or Mg ions are within the ranges already specified for the individual ions at (G) (i) and (ii); and (L) the concentration of NO 2 ions is not more than 1.3 g / L. The composition of claim 4, wherein: (A) the amount of dissolved phosphate ions is from 13 to 18 g / L; (B) the amount of dissolved Zn ions is from 0.71 to 0.87 g / L; (C) the amount of dissolved Cu ions is from 24 to 60 mg / L; (D) the accelerator comprises at least one from 0.01 to 0.2 g / l of nitrite ions and from 0.5 to 2 g / l, measured as a stoichiometric equivalent of hydroxylamine, HAS; (E) total acidity points from 18 to 21; (F) free acid points from 0.35 to 0.65; 2+ (B) the amount of dissolved Zn ions is from 0.60 to 0.95 g / L; (D) the accelerator comprises at least one of from 0.01 to 0.2 g / l of nitrite ions and from 0.5 to 6 g / l, measured as a stoichiometric equivalent of hydroxylamine, a component capable of providing hydroxylamine in aqueous solution; (E) total acid points are from 16 to 22; (F) free acidity points are up to 0.8; and (L) the concentration of NOg ions is not greater than 1.8 g / L. A composition according to claim 3, characterized in that: (B) the amount of dissolved Zn ions is from 0.60 to 0.95 g / L; (D) the accelerator comprises at least one from 0.01 to 0.2 g / l of nitrite ions and from 0.5 to 6 g / l, measured as a stoichiometric equivalent of hydroxylamine, a component capable of providing hydroxylamine in aqueous solution; (E) total acid points are from 16 to 22; (F) free acidity points are from - 0.5 to 0.0; and (L) the concentration of NO 2 ions is not greater than 1.8 g / L. 6. A composition according to claim 5, wherein: (A) the amount of dissolved phosphate ions is from 13 to 18 g / L; (B) the amount of dissolved Zn ions is from 0.71 to 0.87 g / L; (C) the amount of dissolved Cu ions is from 24 to 60 mg / L; (D) the accelerator comprises at least one of from 0.01 to 0.2 g / l nitrite ions and from 0.5 to 2 g / l, measured as a stoichiometric equivalent of hydroxylamine, HAS; (E) total acid points are from 18 to 21; (F) free acidity points are from - 0.5 to - 0.2; (G) (i) the concentration of total Mn ions and Co ions is from 2+ (B) the amount of dissolved Zn ions is from 0.57 to 1.24 g / L; (C) the amount of dissolved Cu ions is from 24 to 74 mg / L; (E) total acid points are from 13 to 24; (F) free acidity points are from - 0.5 to + 1/0; and (L) the concentration of NO 2 ions is not more than 2.0 g / L. The composition of claim 3, wherein: 2- (K) concentration of SO4 ions is not more than 11 g / L; and (1) the concentration of NO 2 ions is not greater than 3.4 g / L. A composition according to claim 2, characterized in that: 2 g / l of m-nitrobenzoate ions, (v) from 0.05 to 2 g / l of p-nitrophenol, and (vi) from 0.1 to 10 g / l, measured as a stoichiometric equivalent of hydroxylamine, components, which is capable of providing hydroxylamine in aqueous solution; (E) total acid points are from 7 to 25; (F) free acidity points are from - 0.5 to + 1.5; (G) the total concentration of Mn and Co ions is from 0.1 to 0.8 g / L; or (ii) the concentration of Mg ions is from 0.5 to 1.0; or (iii) the concentration of both total Mn + ⁺ and C ^{+ +} ions and Mg + ⁺ ions lies within the ranges specified for individual ions in sections (i) and (ii); (J) the concentration of free fluoride, as measured by a fluoride sensitive electrode, is from 1.0 to 4.0 g / L; 2+ (B) the amount of dissolved Zn ions is from 0.45 to 2.0 g / L; (C) the amount of dissolved Cu ions is from 20 to 100 mg / L; (D) the accelerator comprises at least one of (i) from 0.01 to 0.2 g / l nitrite ions, (ii) from 0.5 to 5 g / l (iii) from 0.05 to 2 g / l m nitrobenzenesulfonate ions; A composition according to claim 1, characterized in that: (A) the amount of dissolved phosphate ions is from 5 to 20 g / L; 2+ (C) from 1 to 200 mg / L dissolved Cu ions; (D) an effective amount of a conventional accelerator exclusively from nitrite ions; (E) from 5 to 40 total acidity points; and (F) from - 1.0 to + 3.0 free acid points; and, optionally, (G) up to 2 g / L total Mn and Co ions; and, optionally, (H) up to 2 g / l Mg ions; and optionally (J) up to 5.5 g / L of free fluoride as measured by a fluoride sensitive electrode; and, optionally, (K) not more than 40 g / L of SO4 ions; and, optionally, (L) no more than 4.5 g / L NO 2 ions; and, optionally, (M) not more than 0.2 g / L of Ni ² ions. 2+ (B) from 0.2 to 3 g / L dissolved Zn ions; (3) forming a phosphate coating on the cleaned and activated surface by the method of claim 8; and (4) applying a solid organic substance-based outer coating to the phosphate coating formed in step (3).