Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
  • C23C22/08—Orthophosphates
  • C23C22/18—Orthophosphates containing manganese cations
  • C23C22/182—Orthophosphates containing manganese cations containing also zinc cations
  • C23C22/184—Orthophosphates containing manganese cations containing also zinc cations containing also nickel cations
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/34—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
  • C23C22/36—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates
  • C23C22/364—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates containing also manganese cations
  • C23C22/365—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates containing also manganese cations containing also zinc and nickel cations

Definitions

• the present invention relates to a method for phosphating electrolytically and / or hot-dip galvanized steel strip with the formation of zinc phosphate layers containing manganese and nickel. These manganese and nickel-containing zinc phosphate layers are applied by spraying, splash-dipping and / or dipping with aqueous solutions.
• manganese-modified zinc phosphate coatings are known as a basis of liability for modern coatings.
• the use of manganese ions in addition to zinc and nickel ions in low-zinc phosphating processes has been shown to improve corrosion protection, in particular when using surface-coated thin sheets.
• the incorporation of manganese into the zinc phosphate coatings leads to smaller and more compact crystals with increased stability to alkali.
• the working range of phosphating baths is increased; Aluminum can also be phosphated in combination with steel and electrolytically or hot-dip galvanized steel to form a layer, whereby the generally achieved quality standard is guaranteed.
• DE-A-32 45 411 discloses a process for the phosphating of electrolytically galvanized metal products, in particular electrolytically galvanized steel strips, by short-term treatment with acid phosphating solutions which, in addition to zinc and phosphate ions, can contain further metal cations and / or anions of oxygen-containing acids with accelerating action .
• acid phosphating solutions which, in addition to zinc and phosphate ions, can contain further metal cations and / or anions of oxygen-containing acids with accelerating action .
• zinc phosphate layers with a mass per unit area of less than 2 g / m 2 are formed. It works with acid phosphating solutions, the content of Zn 2 + cations is about 1 to 2.5 g / I, while the free acid content in the range of 0.8 to 3 points and the total acid / free acid ratio in the range of 5 to 10 are held.
• the duration of the treatment should not be significantly longer than 5 s.
• nitrate-containing phosphating baths are used, the weight ratio of Zn 2+ / NO a - in the range from 1: 1 to 1: 8 and the weight ratio of PO 4 3 - / NO 3 - in the range from 1: 0.1 to 1 : 2.5 is held.
• EP-A-0 106 459 discloses a phosphating process in which zinc phosphate coatings containing manganese and nickel are formed.
• the presence of fluoride ions is considered essential, as is the upper limit of 10 g / l nitrate anions.
• a high nickel phosphating process is known from E-B-0 112 826.
• a molar ratio of nickel to zinc in the range from 5.2: 1 to 16: 1 is assumed.
• a phosphating process is known from EP-A-0 175 606, in which the use of iron-containing phosphating baths in particular is used.
• a number of organic substances are also used as accelerators, while the presence of manganese is not necessary.
• the setting of certain ratios of zinc to nickel and zinc to iron is required.
• JP-A-63-227786 - describes a process for the simultaneous degreasing and phosphating of galvanized steel sheet before cathodic electroplating thereof.
• preformed articles made of galvanized steel sheet are treated with acid phosphating solutions which contain the following components: 0.3 to 1.0 g / I Zn 2+ , 0.4 to 3.5 g / I Ni 2+ , 0.1 up to 3.5 g / I Mn 2+ , 10 to 20 g / I P0 4 3- , 0.5 to 1.5 g / IF, 15 g / I N0 3 -, 0.7 to 6 g / I surfactant , 2 to 6 points accelerator, based on the free acid content of the N0 2 -.
• EP-A-0 060 716 relates to a phosphating process for automobile bodies before a cathodic electro-coating thereof.
• the metal surfaces based on steel or zinc are treated with solutions containing 0.5 to 1.5 g / l zinc ions, 5 to 30 g / l phosphate ions, 0.6 to 3 g / l manganese ions and an accelerator.
• these solutions can contain 0.1 to 4 g / l of nickel ions.
• nitrite ions, m-nitrobenzenesulfonate ions and hydrogen peroxide can be used as accelerators, as well as nitrate and chlorine ions.
• the duration of treatment in the immersion process is at least 15 seconds, in particular 30 to 120 seconds.
• the layer weights of the resulting phosphating layers are in the range from 2.0 to 3.2 g / m 2 .
• EP-A-0 219 779 relates to a process for phosphating electrolytically galvanized metal products, preferably electrolytically galvanized steel strips.
• phosphating solutions which contain 0.1 to 0.8 g / l zinc cations and 0.5 to 2.0 g / l manganese cations and some Free acid content in the range of 4 to 8 points and an acid ratio in the range of 2.5 to 5.
• the solutions may additionally contain cobalt, the cobalt content being 1 part cobalt per 100 to 150 parts (Zn 2+ + Mn 2+ ).
• Layer weights of the phosphating layers of less than 2 g / m 2 result with treatment times that are not significantly more than 5 seconds.
• Nitrate serves as an accelerator.
• the object of the present invention was to avoid darkening of the zinc phosphate layers on electrolytically and / or hot-dip galvanized steel strip at treatment times of 3 to 20 s while maintaining the corrosion protection values.
• the nickel content of processes known from the literature should be greatly reduced by substitution with manganese in order to achieve corrosion protection and paint adhesion, as in the trication processes used in the automotive industry, also in the case of continuous strip phosphating.
• the term “electrolytically and / or hot-dip galvanized steel strip” also includes, of course, generally known zinc alloys (for example “Neuralyt”, ZNE electrolytically applied zinc alloy containing 10 to 13% Ni or “Galvannealed”, ZFE electrolytically applied zinc alloy containing Fe) with a.
• zinc alloys for example “Neuralyt”, ZNE electrolytically applied zinc alloy containing 10 to 13% Ni or “Galvannealed”, ZFE electrolytically applied zinc alloy containing Fe
• zinc alloys is generally understood to mean those zinc alloys which contain at least 45% by weight of zinc.
• the above-mentioned objects are achieved by a method for phosphating electrolytically and / or hot-dip galvanized steel strip with the formation of manganese and nickel-containing zinc phosphate layers, which have a mass per unit area of less than 2 g / m 2 , in particular in the range from 0.7 to 1. 6 g / m 2 , by brief treatment with acid phosphating solutions containing Zn 2 + - , Mn 2 + - , Ni 2 + - , P043 + - and NO 3 - -lons, characterized in that
• the duration of the treatment is 3 to 20 s
• the phosphating is carried out in the temperature range from 40 to 70 ° C. and the phosphating solutions - at least at the beginning of the treatment - contain the following constituents or correspond to the following parameters: in which the weight ratio of Ni 2 + cations to NO 3 - anions in the range from 1:10 to 1:60 and the weight ratio of Mn 2+ cations to N0 3 anions is set in the range from 1: 1 to 1:40.
• the above-mentioned content of PO 4 3- anions also includes HPO 4 2- and H 2 P0 4 - anions and undissociated H 3 PO 4 - in the form of the stoichiometric equivalent of P043- Anions - with a.
• the free acid score is accordingly defined as the number of ml 0.1 N NaOH required to titrate 10 ml bath solution against dimethyl yellow, methyl orange or bromophenol blue.
• the total acid score is calculated as the number of ml of 0.1 N NaOH required to titrate 10 ml of bath solution using phenolphthalein as an indicator until the first pink color.
• the phosphating solutions preferably contain no strong oxidizing agents, such as nitrites, chlorates or hydrogen peroxide.
• An essential part of the present invention is the weight ratio of nickel cations to nitrate anions and the weight ratio of manganese cations to nitrate anions.
• the simultaneous use of nickel and manganese cations leads to improved corrosion protection values, but in the processes known from the literature to a darkening of the zinc phosphate layer.
• the coloring of this zinc phosphate layer does not play a major role in the automotive industry, but the color of the zinc phosphate layer is extremely important, for example, in the manufacture of household appliances due to the very thin layers of lacquer that are often applied in the following.
• Another essential criterion of the present invention is the duration of the phosphating treatment. While times above 120 s are usually used for the phosphating in the automotive industry, a time below 1 min is in any case aimed for in the phosphating of galvanized steel strip. For the purposes of the present invention, the duration of the treatment will therefore be between 3 to 20 s.
• the main advantage of the present invention is that zinc phosphate coatings on galvanized steel strip can be produced according to the invention which have a bright surface appearance, although they contain nickel. At the same time, however, the nickel content could be significantly reduced compared to the prior art by substitution with manganese without loss of the corrosion protection value. This is of ecological as well as economic importance, as it is the first time that a manganese-containing trication process has been described for the band sector.
• a preferred embodiment of the present invention is that the weight ratio of nickel cations to nitrate anions is set in the range from 1:20 to 1:60. In the context of the present invention, it was found that an excessively large amount of nitrate has just as negative an effect on the phosphating process as an excessively low nickel content. This has a negative influence on the corrosion protection values. In a further preferred embodiment of the present invention, the weight ratio of manganese cations to nitrate anions is set in the range from 1: 6 to 1:20. This can have a particularly positive influence on the wet paint adhesion.
• a further preferred embodiment of the present invention is characterized in that the phosphating solutions contain a fluoride anion content of 0.1 to 1.0 g / l, preferably 0.4 to 0.6 g / l.
• fluoride anions is the phosphating solutions in the form of hydrofluoric acid or in the form of sodium or Potassium salts added to this acid.
• complex fluoride compounds such as fluoroborates or fluorosilicates can also be used.
• the phosphating itself takes place at moderately elevated temperatures in the range from about 40 to 70 ° C.
• the temperature range from 55 to 65 ° C. can be particularly suitable. Any technically useful way of applying the treatment solution is suitable. In particular, it is therefore possible to carry out the new method both by means of spraying technology and by immersion.
• the electrolytically and / or hot-dip galvanized surface must be completely water-wettable. This is usually the case in continuously operating conveyor systems. If the surface of the galvanized strip is oiled for storage and corrosion protection, this oil must be removed using suitable means and processes that are already known before phosphating.
• the water-wettable galvanized metal surface is then expediently subjected to an activating pretreatment known per se before the phosphating solution is applied. Suitable pretreatment processes are described in particular in DE-A-20 38 105 and DE-A-20 43 085.
• the metal surfaces to be phosphated subsequently are treated with solutions which contain, as activating agents, essentially titanium salts and sodium phosphate together with organic components such as, for example, alkyl phosphonates or polycarboxylic acids.
• Soluble compounds of titanium such as potassium titanium fluoride and in particular titanyl sulfate can preferably be used as the titanium component.
• Disodium orthophosphate is generally used as the sodium phosphate. Titanium-containing compounds and sodium phosphate are used in such proportions that the titanium content is at least 0.005% by weight, based on the weight of the titanium-containing compound and the sodium phosphate.
• the process according to the invention produces zinc phosphate coatings with a weight per unit area of the zinc phosphate layers of less than 2 g / m 2 , which have a closed, finely crystalline structure and give the electrolytically and / or hot-dip galvanized steel strip a desired, uniform, light gray appearance.
• a steel strip phosphated in this way can also be processed without subsequent coating.
• the thin phosphate layers produced by the method according to the invention behave more favorably in many shaping processes than the phosphate layers of a higher mass per unit area produced with the previously usual methods.
• organic coatings applied subsequently also show significantly improved adhesion compared to the prior art, both during and after the shaping processes.
• surface-based masses of the zinc phosphate layer in the range from 0.7 to 1.6 g / m 2 are produced when using electrolytically galvanized steel strip.
• the production of a mass per unit area of the zinc phosphate layer in the range from 0.8 to 1.6 g / m 2 should be emphasized as particularly advantageous.
• the method according to the invention allows the nickel and manganese-containing zinc phosphate layer to be applied by techniques known per se in the prior art, such as spraying, dipping and / or spray-dipping, in particular their combined methods.
• the acid ratio is determined when using electrolytically galvanized steel strip, i.e. the quotient from “total acid” to “free acid” is set in the range from 25: 1 to 10: 1, preferably in the range from 15: 1 to 10: 1.
• the surface layers produced with the aid of the method according to the invention can be used well in all fields in which phosphate coatings are used.
• a particularly advantageous application is the preparation of the metal surfaces for painting, in particular electrocoating.
• a mass per unit area of 0.6 to 1.6 g / m 2 was produced for electrolytically galvanized steel (ZE) and a mass per unit area of the phosphate layer of 0.8 to 1.6 g / m 2 for hot-dip galvanized steel (Z).
• the substrate to be phosphated was selected to be electrolytically galvanized steel on both sides (7.5 / 7.5 ⁇ m zinc) for the test using the VW-P 1210 alternating climate test and hot-dip galvanized steel (10/10 ⁇ m zinc) for the salt spray test.
• Example 1 The sheets obtained with the aid of Example 1 and the comparative example were used to carry out corrosion tests with an alternating climate in accordance with VW standard P 1210 over a test period of 15 and 30 days, and corrosion tests in a salt spray test in accordance with DIN 50 021 SS, 1008 h.
• blistering that occurs in paints is defined by specifying the degree of blistering.
• the degree of bubbles according to this standard is a measure of the formation of bubbles on a coating according to the frequency of the bubbles per unit area and the size of the bubbles.
• the degree of bubbles is indicated by a code letter and a code number for the frequency of the bubbles per unit area as well as a code letter and a code number for the size of the bubbles.
• the code letter and the code m0 mean no bubbles, while m5 defines a certain frequency of bubbles per unit area according to the degree of bubbles according to DIN 53 209.
• the size of the bubbles is given the code letter g and the code number in the range from 0 to 5.
• Code letter and code number g0 has the meaning of freedom from bubbles, while with g5 the size of the bubbles is shown according to the degree of bubbles in DIN 53 209.
• the degree of bubbles is determined, the image of which is most similar to the appearance of the paint.
• the salt spray test according to this standard is used to determine the behavior of paints, coatings and similar coatings when exposed to sprayed sodium chloride solution. If the coating has weak points, pores or injuries, the coating preferably infiltrates from there. This leads to a reduction in adhesion or to loss of adhesion and corrosion of the metallic surface.
• the salt spray test is used so that such errors can be recognized and the infiltration can be determined.
• the test sheet is bombarded with a defined amount of steel shot with a certain grain size distribution.
• a key figure is assigned to the degree of corrosion.
• the key figure 1 denotes an invisible corrosion, while with a key figure 10 practically the entire surface is corroded.
• the sample is bent for 1 to 2 s with different bending radii parallel to the rolling direction by 180 ° , with the coating on the outside.
• the smallest bending radius which allows the sample to bend without tearing, determines the adherence at a 180 ° bend.
• the sheet is bent evenly through 180 ° within 1 to 2 s without an intermediate layer. The sheet is examined immediately after bending with a magnifying glass that magnifies ten times. The test procedure is made more difficult by firmly pressing an adhesive film onto the edge and tearing it off quickly. The amount of lacquer torn off is then assessed.

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• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Treatment Of Metals (AREA)
• Coating With Molten Metal (AREA)

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• 1989
  • 1989-08-17 DE DE3927131A patent/DE3927131A1/de not_active Withdrawn
• 1990
  • 1990-08-08 AU AU61675/90A patent/AU633135B2/en not_active Ceased
  • 1990-08-08 EP EP90912396A patent/EP0486576B1/de not_active Expired - Lifetime
  • 1990-08-08 WO PCT/EP1990/001295 patent/WO1991002829A2/de active IP Right Grant
  • 1990-08-08 CA CA002065004A patent/CA2065004A1/en not_active Abandoned
  • 1990-08-08 ES ES90912396T patent/ES2071110T3/es not_active Expired - Lifetime
  • 1990-08-08 AT AT90912396T patent/ATE121803T1/de not_active IP Right Cessation
  • 1990-08-08 JP JP2511444A patent/JPH04507436A/ja active Pending
  • 1990-08-08 DE DE59008978T patent/DE59008978D1/de not_active Expired - Fee Related
  • 1990-08-15 CN CN90106684A patent/CN1034681C/zh not_active Expired - Fee Related
  • 1990-08-16 ZA ZA906507A patent/ZA906507B/xx unknown

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