TWI787775B - Method for forming a black-passivation layer on a zinc-iron alloy and black-passivation composition - Google Patents

Abstract

The present inventions refers to a method for forming a black-passivation layer on a zinc-iron alloy of a substrate, a black-passivation composition for depositing a black-passivation layer on such, wherein the black-passivation composition comprises one or more than one blackening agent selected from the group consisting of formula (I) and formula (II) as described hereinafter, and a respective use of said blackening agents for blackening a zinc-iron alloy.

Description

Method for forming black passivation layer on zinc-iron alloy and black passivation composition

The present invention relates to a method for forming a black passivation layer on a zinc-iron alloy and a black passivation composition for depositing a black passivation layer thereon, wherein the black passivation composition comprises formula (I) and One or more than one blackening agent of the group consisting of formula (II).

To protect metal substrates from corrosive environmental influences, different methods are available according to the prior art. Applying a protective coating/layer of metal or metal alloy on a metal substrate is a widely used and established method. A well known principle is the deposition of zinc or zinc nickel coatings/layers on metal substrates such as ferrous metal substrates. Such coatings/layers are often referred to as conversion coatings/conversion layers. These conversion coatings/coatings generally comprise the reaction product of a metal substrate and a respective conversion treatment solution (which is insoluble in aqueous media over a wide pH range). To further increase the corrosion resistance, these conversion coatings/conversion layers are additionally passivated with a passivation layer by bringing them into contact with a passivation composition. Such passivation compositions and respective methods are known in the art.

Besides zinc and zinc-nickel coatings/layers, other alloys are becoming more prominent, such as zinc-iron. As nickel becomes more and more problematic with regard to environmental and health issues, less critical alternatives are needed.

In many cases, the passivation composition additionally modifies the color of the conversion coating/conversion layer, for example, to bluish or even dark black. Depending on the application, such color modifications are often for optical reasons and are particularly desirable in the automotive sector.

However, for some conversion coatings/conversion layers, suitable color modification by means of passivation compositions is not available at all, provides insufficient color modification, deteriorates corrosion resistance after color modification, or requires complex passivation compositions, which Complex passivation compositions require handling. This is especially true for zinc-iron conversion coatings/conversion layers (eg, substrates protected with zinc-iron layers). There is still a need to blacken it without reducing the corrosion resistance.

EP 1 816 234 B1 relates to an aqueous passivating coating composition for zinc or zinc alloys and a method for its use.

CN 104651823 A relates to a cobalt-free, environmentally friendly trivalent chromium black passivation liquid, which contains tungsten disulfide particles as a blackening agent. CN'823 is silent about zinc-iron alloys.

WO 97/13888 A1 relates to a chromate-free corrosion inhibiting coating composition capable of protecting a wide variety of metal surfaces.

WO 02/49960 A2 relates to specific tripolyphosphates, mixtures thereof, and the use as anticorrosion agents and as biocides (antimicrobials) and, where applicable, as encrustation inhibitors.

EP 3 360 989 A1 relates to a method for electrolytically passivating the outermost chromium or outermost chromium alloy layer to increase its corrosion resistance.

US 2004/0170848 A1 relates to a corrosion inhibiting composition for coating articles or substrates such as metals, metal coatings, chromated metal coatings and the like, comprising film-forming compounds such as waxes or polymers) and sulfide salts or sulfur-containing compounds or derivatives of sulfur-containing compounds. US'848 is silent about blackening.

Although black passivation compositions are described in the art, there is a continuing need to improve the blackening of zinc-iron conversion coatings/conversion layers. Object of the invention

It is therefore an object of the present invention to provide a method for forming a black passivation layer, in particular on zinc-iron alloys, which has improved blackening qualities without compromising corrosion resistance. In addition, corresponding black passivation compositions are also required.

Furthermore, the aim was to overcome the above-mentioned disadvantages and in particular to provide a method (together with a corresponding composition) which is easy to handle and avoids deposition due to being substantially free of particles.

(I)， 其中 R¹ 及R² 獨立地選自由氫及C1至C5烷基組成之群， R³ 係選自由磺酸、羧酸、烷基羧酸、磷酸、其鹽及酯組成之群，且 n為1、2、3、4或5，

(II)， 其中 R⁴ 係選自由磺酸、羧酸、烷基羧酸、磷酸、其鹽及酯組成之群，且 m為1、2、3、4或5，及 (ii)選自由三價鉻、鈦及鋯組成之群之一種或超過一種金屬離子，及 (c)使該基材與該黑色鈍化組合物接觸使得該黑色鈍化層形成於該鋅鐵合金上。The above-mentioned objects are solved by a method for forming a black passivation layer on a zinc-iron alloy, the method comprising the following steps: (a) providing a substrate comprising the zinc-iron alloy, (b) providing a method for forming a black passivation layer on the zinc-iron alloy A black passivation composition for depositing the black passivation layer, the composition comprising (i) one or more than one blackening agent selected from the group consisting of formula (I) and formula (II),

(I), wherein R ¹ and R ² are independently selected from the group consisting of hydrogen and C1 to C5 alkyl, R ³ is selected from the group consisting of sulfonic acid, carboxylic acid, alkyl carboxylic acid, phosphoric acid, salts and esters thereof , and n is 1, 2, 3, 4 or 5,

(II), wherein R is selected from the group consisting of sulfonic acid, carboxylic acid, alkylcarboxylic acid, phosphoric acid, salts and esters thereof, and m is 1, 2, 3, ⁴ or 5, and (ii) is selected from One or more than one metal ion of the group consisting of trivalent chromium, titanium and zirconium, and (c) contacting the substrate with the black passivation composition so that the black passivation layer is formed on the zinc-iron alloy.

By utilizing the one or more than one blackening agents, excellent blackening of zinc-iron alloys together with good corrosion resistance is obtained. In addition, the method of the present invention is simple and can be easily performed. Furthermore, our own experiments have shown that the blackening obtained by means of the method of the invention and the corresponding black passivation composition of the invention is highly specific for zinc-iron alloys. Self-experiments have confirmed that zinc and zinc-nickel alloys alone are not blackened. Further details are provided in the Examples section herein below.

The present invention also relates to a corresponding black passivation composition as further described herein below and the respective use of the one or more than one blackening agent for blackening zinc-iron alloys. In general, the features described with respect to the method of the invention, in particular the features described as preferred also apply to the black passivation composition of the invention, best apply to the black passivation composition described as preferred, and equally apply to The use according to the invention is best suited for the use described as preferred.

In the context of the present invention, trivalent chromium ions refer to chromium ions having an oxidation number of +3 (also called trivalent chromium ions), including individual free forms and complex forms. Accordingly, mutatis mutandis apply to the corresponding metal ions of titanium and zirconium.

In the context of the present invention, the term "black passivation layer" also denotes a black conversion layer. Substrate

Preferably, based on the CIELAB color space definition, the black passivation layer has a blackness value L* of 40 or less, preferably 33 or less, most preferably 25 or less.

As mentioned above, the method of the present invention is highly specific for zinc-iron alloys. Preferred is the method of the invention, wherein in the zinc-iron alloy the amount of iron is in the range of 0.1% to 30% by weight, preferably 0.6% to 28% by weight, more preferably 2.1% by weight, based on the total weight of the zinc-iron alloy % to 25 wt%, even better 3.5 wt% to 22 wt%, optimally 4.9 wt% to 18 wt%, even optimally 6.1 wt% to 15 wt%. The optimum amount of iron ranges from 4.9% to 30% by weight. In this excellent range, excellent blackening is easily obtained.

The method of the present invention is generally applicable to zinc-iron alloys. Preferred is the method of the invention, wherein the zinc-iron alloy is present on the substrate as a layer, preferably as a self-plating process, most preferably from a zinc-iron electroplating process. Therefore, the method of the present invention is preferred, wherein the zinc-iron alloy is different from the rest of the substrate. In this way, the substrate is generally protected from corrosion.

Preferred is the method of the invention, wherein the substrate comprises iron. This means that the substrate preferably comprises a base material, preferably a subway base material, more preferably steel, on which a zinc-iron alloy is deposited. Thus, the zinc-iron alloy is distinct from the remainder of the substrate (ie, represented by the base material).

However, the method of the invention is preferred in rare cases where the substrate comprises a zinc-iron alloy in the sense that the substrate itself is made of the zinc-iron alloy. In other words, preferably, the base material has been a zinc-iron alloy and thus, the base material is the substrate.

Preferably the method of the invention wherein the substrate is a metal or metal alloy substrate, preferably the substrate comprises iron, most preferably the substrate comprises iron and is different from a zinc-iron alloy.

Preferred is the method of the invention, wherein the substrate is a workpiece requiring anodic corrosion resistance, preferably due to environmentally induced corrosion.

In general, preferred substrates are selected from the group consisting of screws, bolts, nuts, and automotive parts.

Preferred is the method of the invention, wherein more than one substrate is provided in step (a), preferably a plurality of substrates are provided in step (a). This applies in particular if the base material refers to screws, bolts and nuts.

Preferred is the method of the invention, wherein the substrates, preferably the substrates, are provided in tubs or secured to racks. Therefore, the method of the present invention is applicable to both types. black passivation composition

In the method of the invention, a black passivation composition is utilized, preferably a black passivation composition of the invention (see further text below).

Preferably, the black passivation composition is also called conversion composition.

Preferably the method of the present invention, wherein the black passivation composition is aqueous (i.e., contains water), wherein preferably the water has more than 50% by volume based on the total volume of the black passivation composition, more preferably 75% by volume or More, optimally a concentration of 90% by volume or more. Excellent, water is the only solvent.

Preferably, the black passivation composition is a solution. Therefore, the method of the present invention is preferred, wherein the black passivation composition is substantially free of particles (including colloids), preferably does not contain particles (including colloids).

The method of the present invention is preferred, wherein the black passivation composition is acidic, preferably has a value of 1.0 to 4.5, preferably 1.2 to 4.0, more preferably 1.4 to 3.3, even more preferably 1.5 to 2.8, and most preferably 1.6 to a pH of 2.2.

As mentioned above, the black passivation composition comprises one or more than one blackening agent as defined above.

As indicated by each of formulas (I) and (II), the one or more than one blackening agent utilized in the black passivation composition is an organic blackening agent. It is preferably the method of the present invention, wherein the black passivation composition is substantially free of inorganic blackening agents, preferably does not contain inorganic blackening agents. Inorganic blackening agents are disclosed in CN 104651823 A, for example.

The method of the present invention is preferred, wherein the black passivation composition contains at least one or more than one (preferably one) blackening agent of formula (I). According to own experiments, the blackening agents of formula (I) give excellent results (see examples below).

Only in some cases, the method of the present invention is preferred, wherein the black passivation composition is substantially free of the blackening agent of formula (II), preferably does not contain the blackening agent of formula (II). Optimally, this applies if the black passivating composition already comprises a blackening agent of formula (I).

Generally preferred is the method of the present invention, wherein in the black passivation composition, one or more than one blackening agent selected from the group consisting of formula (I) and formula (II) is the only blackening agent in the black passivation composition .

Preferred is the method of the present invention, wherein in the black passivation composition, the one or more than one blackening agent has a range from 0.2 mmol/L to 100 mmol/L, preferably 0.3 mmol/L based on the total volume of the black passivation composition. Total of mmol/L to 80 mmol/L, more preferably 0.4 mmol/L to 60 mmol/L, even better 0.8 mmol/L to 45 mmol/L, optimally 1.6 mmol/L to 38 mmol/L concentration.

Specifically, the method of the present invention is preferred, wherein the black passivation composition ranges from 0.4 mmol/L to 25.0 mmol/L, preferably 0.6 mmol/L to 20.0 mmol based on the total volume of the black passivation composition /L, more preferably 0.8 mmol/L to 12.0 mmol/L, even better 1.0 mmol/L to 10.0 mmol/L, the best total concentration of 1.2 mmol/L to 8.0 mmol/L comprises formula (I) One or more than one (preferably one) blackening agent. Optimally, in combination with this total concentration, the compound of formula (I) is the sole blackening agent in the black passivation composition utilized in the method of the invention. Surprisingly, excellent blackening was observed even with relatively low total concentrations of the compound of formula (I), including a total concentration of 0.4 mmol/L. It is highly desirable to maintain relatively low concentrations of blackening agents so that the lifetime of the respective black passivating composition is as long as possible. Excellent total concentrations range from 0.4 mmol/L to 8.0 mmol/L.

Preferred is the method of the present invention, wherein R ¹ and R ² are independently selected from branched and unbranched C1 to C5 alkyl groups, preferably unbranched C1 to C5 alkyl groups.

Preferred is the method of the present invention, wherein in ^R3 and R4, the salts are independently selected from the group consisting of ^ammonium salts and basic salts, preferably the group consisting of ammonium, sodium and potassium.

Preferred is the method of the present invention, wherein R and R are independently selected from hydrogen, methyl, ethyl, ¹ -propyl, ² -propyl, 1-butyl, 2-butyl and tert-butyl The group, preferably hydrogen, methyl, ethyl, 1-propyl and 2-propyl, most preferably hydrogen and methyl.

Preferred are methods of the invention wherein at least ^one of R1 and ^R2 is an alkyl group, preferably as described above.

Preferred is the method of the present invention, wherein n is 2, 3 or 4, preferably 3.

In the method of the present invention, R ³ is selected from the group consisting of sulfonic acid, carboxylic acid, alkyl carboxylic acid, phosphoric acid, salts and esters thereof.

Sulfonic acid preferably means ~ _SO3H , wherein "~" denotes a covalent bond connecting this group to the rest of the compound of formula (I). Carboxylic acid preferably means ~COOH, where "~" denotes a covalent bond connecting this group to the rest of the compound of formula (I). Alkyl carboxylic acid preferably means a saturated branched or unbranched chain alkyl group comprising one or more than one (preferably two) carboxylic acid groups, more preferably means one or more than one (preferably two) carboxylic acid groups Two) saturated branched or unbranched C1 to C6 alkyl (preferably C2 to C4 alkyl) of a carboxylic acid group, even more preferably it comprises ~C(COOH)(CH ₂ ) _k COOH, wherein "~" denotes a covalent bond connecting this group to the rest of the compound of formula (I) and k is an integer ranging from 1 to 5, optimally it includes ~C(COOH) _CH2COOH . Phosphoric _acid preferably means ~PO3H2, where "~" denotes a covalent bond linking this group to the rest of the compound of _formula (I). Preferably, the above mentioned for R ³ applies mutatis mutandis to R ⁴ in formula (II).

Preferably it is the method of the present invention, wherein R ³ includes at least sulfonic acid, its salt and/or ester, preferably R ³ includes at least sulfonic acid, its salt and/or ester, and n is 3.

More preferably the method of the present invention, wherein R ³ is selected from the group consisting of sulfonic acid, carboxylic acid, phosphoric acid and salts thereof, most preferably, R ³ includes at least sulfonic acid and/or its salt, preferably R ³ includes at least Sulfonic acid and/or its salt, and n is 3.

The most preferred method of the present invention, wherein formula (I) includes the compound 3-(N,N-dimethylthioaminoformyl)-thiopropanesulfonic acid, its salt and/or ester, preferably 3- (N,N-Dimethylthioaminoformyl)-thiopropanesulfonic acid and/or its salts.

Preferred is the method of the present invention, wherein m is 2, 3 or 4, preferably 3.

Preferably it is the method of the present invention, wherein R ⁴ includes at least sulfonic acid, its salt and/or ester, preferably R ⁴ includes at least sulfonic acid, its salt and/or ester, and m is 3.

More preferably the method of the present invention, wherein R ⁴ is selected from the group consisting of sulfonic acid, carboxylic acid, phosphoric acid and salts thereof, most preferably, R ⁴ includes at least sulfonic acid and/or its salts, preferably R ⁴ includes at least Sulfonic acid and/or its salt, and m is 3.

Best is the method of the present invention, wherein formula (II) includes compound 3-(2-benzothiazolylthio)-1-propanesulfonic acid, its salt and/or ester, preferably 3-(2-benzo Thiazolylthio)-1-propanesulfonic acid and/or its salts.

The black passivation composition utilized in the method of the present invention comprises one or more than one metal ion selected from the group consisting of trivalent chromium, titanium and zirconium. Although significant blackening of zinc-iron alloys has been observed even in the absence of these metal ions (i.e. in the complete absence of these and other transition metal ions), in order to obtain significant corrosion resistance in addition to the blackening effect properties, these metal ion systems are particularly beneficial. Although some corrosion resistance exists in some cases, the corrosion resistance can thus be significantly increased further.

Preferred is the method of the present invention, wherein the one or more than one metal ion is selected from the group consisting of trivalent chromium and titanium. More preferably the method of the present invention, wherein the one or more than one metal ion comprises at least trivalent chromium, most preferably the one or more than one metal ion is trivalent chromium. Own experiments have shown that excellent corrosion resistance results are obtained with trivalent chromium ions.

Preferred is the method of the present invention, wherein the metal ions of trivalent chromium are derived from organic and/or inorganic sources of trivalent chromium ions, preferably from inorganic sources of trivalent chromium ions. Excellent sources of trivalent chromium ions are organic and/or inorganic sources of trivalent chromium ions. A preferred source of organic trivalent chromium ions is trivalent chromium citrate. A preferred source of inorganic trivalent chromium ions is trivalent chromium chloride hexahydrate.

Preferred is the method of the present invention, wherein the one or more than one metal ion has a range from 0.1 g/L to 30 g/L, preferably 0.2 g/L based on the total volume of the black passivation composition and based on the mass of free ions. A total concentration of L to 20 g/L, more preferably 0.5 g/L to 14 g/L, even better 0.8 g/L to 10 g/L, most preferably 1.3 g/L to 6.0 g/L. Excellent total concentrations range from 0.1 g/L to 4.0 g/L. If the total concentration is significantly below 0.1 g/L, the specific required corrosion resistance is not achieved in many cases. Conversely, if the total concentration is significantly higher than 30 g/L, no further benefit is identified and the cost is generally unacceptable.

Because the trivalent chromium ion system is preferred, it is preferably the method of the present invention, wherein the metal ion of trivalent chromium has a range of 0.1 g/L to 8.0 g/L based on the total volume of the black passivation composition, preferably 0.2 g/L to 7.1 g/L, more preferably 0.5 g/L to 6.1 g/L, even better 0.8 g/L to 5.0 g/L, most preferably 1.0 g/L to 3.5 g/L concentration. Optimally, the above mentioned total concentration of metal ions of trivalent chromium applies, provided that this plasma is the only transition metal ion in the black passivating composition.

In the following, a number of compounds and ions are listed which are preferably not included in the black passivation composition utilized in the method of the present invention. Such compounds/ions are not helpful or even have deleterious effects in addressing the goals mentioned in the summary above and should therefore be avoided. In a few cases, the presence of other compounds/ions is unavoidable after the use of black passivation compositions. In general, relatively simple black passivation compositions are preferred.

Preferred is the method of the present invention, wherein the black passivating composition is substantially free, preferably free of hexavalent chromium. This includes any compounds and ions comprising chromium having an oxidation number of (+VI). The method of the present invention avoids any utilization of hexavalent chromium as a very important goal due to its environmental and health concerns.

Preferred is the method of the present invention, wherein the black passivation composition is substantially free, preferably free of thioglycolic acid and its salts. However, in some cases, the method of the present invention is preferred, wherein the black passivation composition comprises in addition to the one or more than one blackening agent selected from the group consisting of formula (I) and formula (II) as defined above thioglycolic acid and/or its salts. Although own experiments (data not shown) indicate that in many cases the mere presence of thioglycolic acid and/or its salts also causes significant darkening, the results obtained are comparable to those obtained with the blackening agents of formulas (I) and (II) The effect is relatively poor.

Preferred is the method of the present invention, wherein the black passivation composition is substantially free of, preferably free of, nickel ions, preferably substantially free of, preferably free of nickel.

Preferred is the method of the present invention, wherein the black passivation composition is substantially free, preferably free of intentionally added zinc ions. If zinc ions are present in the black passivation composition, they are released/dissolved from the zinc-iron alloy after utilization of the black passivation composition. Therefore, the method of the invention is preferred, with the proviso that if zinc ions are present in the black passivating composition, they are released from the zinc-iron alloy. In other words, if zinc ions are present, the source is zinc-iron alloy. After setting up the respective black passivation composition, generally no zinc ions are present. After starting the method of the present invention, the total concentration is very low. The overall concentration generally increases after utilizing a black passivating composition. Therefore, preferably, after carrying out step (C) several times, zinc ions are based on the total volume of the black passivation composition 10 g/L or less, preferably 8 g/L or less, most preferably 5 g /L or below the total concentration exists.

Preferred is the method of the present invention, wherein the black passivation composition is substantially free of, preferably free of, silver ions, preferably substantially free of, preferably free of silver.

Preferably it is the method of the present invention, wherein the black passivation composition is substantially free of, preferably free of, nicotinic acid and its salts.

Preferably it is the method of the present invention, wherein the black passivation composition is substantially free, preferably does not contain phytic acid and its salts.

In most cases, the method of the present invention is preferred, wherein the black passivation composition is substantially free, preferably contains no intentionally added disulfides. This preferably means that the black passivation composition is substantially free, preferably free of intentionally added ionic disulfides and compounds comprising covalent disulfides. Then, only in very rare cases, the method according to the invention is preferred, wherein the black passivation composition comprises disulfides, preferably ionic disulfides and/or compounds comprising covalent disulfides. In general, however, the absence of such compounds is generally preferred.

Preferred is the method of the present invention, wherein the black passivation composition is substantially free, preferably does not contain intentionally added iron ions. If iron ions are present in the black passivating composition, they are released/dissolved from the zinc-iron alloy after utilization of the black passivating composition. After setting up the respective black passivation composition, generally no iron ions are present. After starting the method of the present invention, the total concentration is very low. The overall concentration generally increases after utilizing a black passivating composition. Therefore, preferably, after carrying out step (C) several times, iron ions are based on the total volume of the black passivation composition 1 g/L or less, preferably 0.8 g/L or less, and most preferably 0.5 g /L or below the total concentration exists.

Preferred is the method of the present invention, wherein the black passivation composition is substantially free, preferably free of tungsten ions.

Even more preferred is the method of the present invention, wherein the black passivating composition is substantially free, preferably free of tungsten.

Preferably it is the method of the present invention, wherein the black passivation composition is substantially free of, preferably free of, tungsten disulfide particles, preferably substantially free of, preferably free of tungsten disulfide.

Preferred is the method of the present invention, wherein the black passivation composition is substantially free, preferably free of thiodiethylene glycol.

Preferably the method of the present invention, wherein the black passivation composition is substantially free of, preferably does not contain silicon dioxide, silicate, silane and silane-containing compounds, preferably substantially free of, preferably does not contain Silicon compounds. Only in very rare cases is the method according to the invention preferred, wherein the black passivating composition comprises silanes and/or silane-containing compounds. It is assumed that in some cases the presence of silanes and/or silane-containing compounds positively affects the corrosion resistance of the black passivation layer. In many cases, however, excellent corrosion resistance has been achieved even without the need for the presence of silanes and/or silane-containing compounds.

Preferred is the method of the present invention, wherein the black passivation composition is substantially free, preferably free of cobalt ions, preferably substantially free, preferably free of cobalt. The presence of cobalt is increasingly becoming an environmental issue. Only in very rare cases, the method of the present invention is preferred, wherein the black passivation composition contains cobalt ions and/or cobalt-containing compounds. The presence of cobalt generally increases the corrosion resistance of heat-treated substrates having a black passivation layer obtained by the method of the invention.

Preferably the method of the present invention, wherein the black passivation composition further comprises (iii) one or more than one halide ion, and/or (iv) One or more than one carboxylic acid and/or salts thereof.

The halide ions are usually counter ions of one or more than one metal ion selected from the group consisting of trivalent chromium, titanium and zirconium.

Preferred is the method of the present invention, wherein the one or more than one halide ion has a total volume based on the black passivation composition of 1 g/L to 18 g/L, preferably 2 g/L to 15 g/L, or even More preferably 3 g/L to 12 g/L, optimally 4 g/L to 10 g/L, even optimally 6 g/L to 9 g/L total concentration.

Preferred is the method of the invention, wherein the one or more than one halide ion comprises chloride and/or fluoride. In some cases, fluorine is preferably also used as a complexing agent for metal ions, most preferably if the one or more than one metal ions are selected from the group consisting of titanium and zirconium. Bromide ions are preferably not included in the black passivation composition.

More preferably, the chloride ion has a total volume based on the black passivation composition of 1 g/L to 18 g/L, preferably 2 g/L to 15 g/L, even more preferably 3 g/L to 12 g/L g/L, optimally 4 g/L to 10 g/L, even optimally 6 g/L to 9 g/L total concentration. Optimally, chloride ions are the only halide ions in the black passivation composition.

The one or more than one carboxylic acid and/or salts thereof are generally used as complexing agents for the one or more than one metal ion selected from the group consisting of trivalent chromium, titanium and zirconium, most preferably trivalent chromium.

Preferred is the method of the present invention, wherein the one or more than one carboxylic acid and/or salt thereof comprises dicarboxylic acid, tricarboxylic acid and/or salt thereof.

Preferred dicarboxylic acids and/or their salts include C2 to C6 dicarboxylic acids and/or their salts, preferably oxalic acid, malonic acid and/or their salts, most preferably oxalic acid and/or their salts.

Preferred tricarboxylic acids and/or salts thereof include citric acid and/or salts thereof.

Preferred is the method of the present invention, wherein the one or more than one carboxylic acid and its salts have a total volume based on the black passivation composition of 0.5 mmol/L to 120 mmol/L, preferably 8 mmol/L to 105 mmol/L A total concentration of L, even more preferably 15 mmol/L to 90 mmol/L, optimally 30 mmol/L to 80 mmol/L, even optimally 45 mmol/L to 70 mmol/L. More preferably, the above total concentrations apply, provided that the black passivation composition comprises at least one or more than one dicarboxylic acid and/or salt thereof.

Even more preferably, oxalic acid and salts thereof have a total volume based on the black passivation composition of 0.5 mmol/L to 120 mmol/L, preferably 8 mmol/L to 105 mmol/L, even more preferably 15 mmol/L L to 90 mmol/L, optimally 30 mmol/L to 80 mmol/L, even optimally 45 mmol/L to 70 mmol/L total concentration. Most preferably, oxalic acid and its salts are the only dicarboxylic acids and their salts in the black passivation composition, preferably the only carboxylic acids and their salts in the black passivation composition.

In some cases, the method of the present invention is preferred, wherein the black passivation composition comprises citric acid and/or its salt, preferably 0.5 mmol/L to 120 mmol/L based on the total volume of the black passivation composition , preferably 8 mmol/L to 105 mmol/L, even more preferably 15 mmol/L to 90 mmol/L, optimally 30 mmol/L to 80 mmol/L, even optimally 45 mmol/L to The total concentration of 70 mmol/L. In such cases, citric acid and its salts are preferably the only tricarboxylic acids and their salts in the black passivating composition, most preferably the only carboxylic acids and their salts in the black passivating composition.

Preferably the method of the present invention, wherein the black passivation composition further comprises (v) Nitrate ion.

Nitrate ions preferably act as oxidizing agents in black passivating compositions.

It is preferably the method of the present invention, wherein the nitrate ion has a range from 0.1 g/L to 20 g/L based on the total volume of the black passivation composition, preferably 0.4 g/L to 15 g/L, even better The total concentration is preferably 0.8 g/L to 11 g/L, optimally 1.2 g/L to 7 g/L, even optimally 1.7 g/L to 4.5 g/L. Contact with black passivating composition ( step (c))

In step (c), the substrate is brought into contact with a black passivation composition, preferably as described above, more preferably as described above as preferred.

Preferably it is the method of the present invention, wherein in step (c), the black passivation composition has a temperature of 10°C to 80°C, preferably 15°C to 65°C, even more preferably 19°C to 45°C, most preferably Temperature in the range of 22°C to 38°C. If the temperature exceeds 80° C. significantly, an undesirably rapid dissolution (stripping) of the zinc-iron alloy affecting the corrosion resistance is observed in many cases. However, if the temperature is too low, the contacting in step (c) is in many cases undesirably long.

Preferred is the method of the invention, wherein in step (c) the contacting is carried out for a duration of 10 seconds to 200 seconds, preferably 20 seconds to 160 seconds, even better 40 seconds to 130 seconds, most preferably 60 seconds to 100 seconds time period of seconds. If the time period exceeds 200 seconds significantly, an undesirably rapid dissolution (stripping) of the zinc-iron alloy affecting the corrosion resistance is observed in many cases. However, if the time period is too short, the blackening is generally insufficient and the optical appearance is thus negatively affected.

Preferred is the method of the invention, wherein step (c) is carried out without application of electric current. Preferably, in step (c), the substrate is dipped into the black passivation composition. Post-processing

As shown in the examples below, if indeed excellent corrosion resistance was obtained after step (c), the substrate was further treated to increase the corrosion resistance.

Generally preferred is the method of the invention, wherein the substrate to be obtained after step (c) of the method of the invention is additionally treated with a post-dipping composition and/or a sealant composition, preferably in this order as outlined below or in reverse order.

The method of the present invention is preferred, wherein step (c) is followed by step (d) Contacting the substrate obtained after step (c) with the post-dip composition such that a post-dipped substrate is obtained.

Preferred is the method of the invention, wherein the post-dip composition is acidic, preferably having a pH ranging from 3.0 to 6.8, more preferably 3.5 to 6.5, even more preferably 4.0 to 6.3, most preferably 4.3 to 6.0.

Preferred is the method of the invention wherein the post-dip composition comprises trivalent chromium ions.

Preferred is the method of the present invention, wherein the sealant composition is substantially free, preferably free of hexavalent chromium-containing compounds and ions.

Preferred is the method of the invention wherein the post-dip composition comprises phosphate ions.

Preferred is the method of the invention, wherein the post-dip composition comprises one or more than one wetting agent.

Preferred is the method of the invention, wherein the post-dip composition comprises one or more than one complexing agent, preferably directed against trivalent chromium ions.

Preferred is the method of the present invention, wherein in step (d), the post-dip composition has a temperature of 18°C to 60°C, preferably 20°C to 58°C, more preferably 28°C to 56°C, even more preferably 33°C A temperature in the range of °C to 54 °C, optimally 38 °C to 50 °C.

Preferred is the method of the present invention, wherein in step (d), contacting is carried out for a duration of 5 seconds to 200 seconds, preferably 10 seconds to 140 seconds, even better 20 seconds to 100 seconds, most preferably 30 seconds to 70 seconds time period of seconds.

The method of the present invention is preferred, wherein step (d) is followed by step (e) contacting the substrate obtained after step (d) with a sealant composition such that a sealed substrate is obtained.

Preferably the method of the present invention, wherein the sealant composition is alkaline, preferably has a range of 9 or higher, more preferably 9.1 to 12, even more preferably 9.3 to 11, most preferably 9.5 to 10.5 pH.

Preferred is the method of the present invention, wherein the sealant composition comprises two or more organic compounds.

Preferred is the method of the present invention, wherein the sealant composition is substantially free, preferably free, of trivalent chromium ions.

Preferred is the method of the present invention, wherein the sealant composition comprises at least one organic polymer, preferably comprising polyurethane, polyolefin (preferably polyethylene), polyfluoroolefin (preferably polytetra vinyl fluoride) and/or polyacrylate.

Preferred is the method of the invention, wherein the sealant composition comprises one or more than one wax.

Preferred is the method of the invention, wherein the sealant composition comprises one or more than one silicon-containing compound, preferably at least one silane and/or at least one inorganic silicate. Preferably, the at least one inorganic silicate is colloidal.

Preferably the method of the present invention, wherein in step (e), the sealant composition has a temperature of 15°C to 35°C, preferably 17°C to 30°C, more preferably 19°C to 27°C, most preferably 21°C Temperature in the range of 25°C.

Preferred is the method of the invention, wherein in step (e) the contacting is carried out for a duration of 5 seconds to 200 seconds, preferably 10 seconds to 140 seconds, even better 20 seconds to 100 seconds, most preferably 30 seconds to 70 seconds time period of seconds.

When steps (d) and (e) are performed in this sequence as outlined above, not only an excellent black passivation layer is obtained, but additionally excellent corrosion resistance, optimally up to 480 hours, based on ISO 9227, 5% white rust limit.

The method of the present invention is preferred, wherein step (e) is followed by step (f) drying the substrate obtained after step (e).

Preferred is the process of the invention, wherein step (f ).

Preferred is the method of the present invention, wherein step (f) is carried out for a period of 2 minutes to 20 minutes, preferably 3 minutes to 16 minutes, even more preferably 4 minutes to 13 minutes, most preferably 6 minutes to 10 minutes .

Preferably, the drying step (preferably as defined above) is also carried out after one or more than one of the preceding steps, eg after step (c), step (d) etc. Very preferred is the process of the invention, wherein the drying step (preferably as defined in step (f)) is carried out after step (d) and before step (e). This is excellent because in step (d) the post-dip composition is acidic, whereas in step (e) the sealant composition is alkaline.

(I)， 其中 R¹ 及R² 獨立地選自由氫及C1至C5烷基組成之群， R³ 係選自由磺酸、羧酸、烷基羧酸、磷酸、其鹽及酯組成之群，且 n為1、2、3、4或5，

(II)， 其中 R⁴ 係選自由磺酸、羧酸、烷基羧酸、磷酸、其鹽及酯組成之群，且 m為1、2、3、4或5，及 (ii) 一種或超過一種金屬離子，該金屬離子選自由三價鉻、鈦及鋯組成之群， 限制條件為 -該黑色鈍化組合物實質上無，較佳地不包含鎳離子、鈷離子及鎢離子。Furthermore, the present invention relates to a black passivation composition for depositing a black passivation layer on a zinc-iron alloy, the composition comprising (i) one or more than one blackening agent selected from the group consisting of formula (I) and formula (II) the group formed,

(I), wherein R ¹ and R ² are independently selected from the group consisting of hydrogen and C1 to C5 alkyl, R ³ is selected from the group consisting of sulfonic acid, carboxylic acid, alkyl carboxylic acid, phosphoric acid, salts and esters thereof , and n is 1, 2, 3, 4 or 5,

(II), wherein R is selected from the group consisting of sulfonic acid, carboxylic acid, alkylcarboxylic acid, phosphoric acid, salts and esters thereof, and m is 1, 2, 3, ⁴ or 5, and (ii) one or More than one metal ion, the metal ion is selected from the group consisting of trivalent chromium, titanium and zirconium, with the proviso that - the black passivation composition is substantially free of, preferably free of, nickel ions, cobalt ions and tungsten ions.

Specifically, it is preferably the black passivation composition of the present invention, wherein the black passivation composition is substantially free of intentionally added zinc ions, preferably does not contain intentionally added zinc ions. Optimally, in view of the method according to the invention, what has been said above specifically with regard to zinc ions also applies to the black passivating composition according to the invention.

Preferably, the above-mentioned black passivation composition used in the method of the present invention (specifically defined as the preferred one) is also applicable to the black passivation composition of the present invention. This applies in particular to compounds and ions that are not present in the black passivating composition utilized in the method of the invention.

(I)， 其中 R¹ 及R² 獨立地選自由氫及C1至C5烷基組成之群， R³ 係選自由磺酸、羧酸、烷基羧酸、磷酸、其鹽及酯組成之群，且 n為1、2、3、4或5，

(II)， 其中 R⁴ 係選自由磺酸、羧酸、烷基羧酸、磷酸、其鹽及酯組成之群，且 m為1、2、3、4或5， 其用於將鋅鐵合金發黑。In addition, the present invention relates to the use of one or more than one blackening agent selected from the group consisting of formula (I) and formula (II)

(I), wherein R ¹ and R ² are independently selected from the group consisting of hydrogen and C1 to C5 alkyl, R ³ is selected from the group consisting of sulfonic acid, carboxylic acid, alkyl carboxylic acid, phosphoric acid, salts and esters thereof , and n is 1, 2, 3, 4 or 5,

(II), wherein R is selected from the group consisting of sulfonic acid, carboxylic acid, alkyl carboxylic acid, phosphoric acid, salts and esters thereof, and m is 1, 2, 3, ⁴ or 5, which is used for zinc-iron alloy blackened.

Preferably, the above-mentioned one or more than one blackening agent of formula (I) and (II) in the black passivation composition utilized in the method of the present invention (specifically defined as the preferred one) is also applicable to Uses of the present invention.

The invention is described in more detail by the following non-limiting examples. example

In the examples, various test passivation compositions were prepared using the numbers introduced in Table 1 below, each composition being aqueous and generally comprising metal ion species; if chromium ions were utilized, 6 g/L to 8 g/L chloride ions; If chromium ions are used, 50 mmol/L to 70 mmol/L oxalic acid or if titanium ions and zirconium ions are used, each 10 mmol/L to 300 mmol/L fluoride ions are used as complexing agents; about 1 g/L to 7 g /L nitrate ion; and one of the following compounds abbreviated as follows: DPS: 3-(N,N-dimethylthioaminoformyl)-thiopropanesulfonic acid sodium salt; also known as Raluplate DPS (CAS 18880-36-9; Raschig company); formula (I) compound, wherein R ¹ and R ² are methyl, R ³ is the sodium salt of sulfonic acid, and n is 3; ZPS: 3-(2-benzene (Thiazolylthio)-1-propanesulfonic acid sodium salt; also known as Raluplate ZPS (CAS 49625-94-7; Raschig Company); formula (II) compound, wherein R ⁴ is the sodium salt of sulfonic acid, and m is 3; SPS: two-(3-sulfopropyl)-disodium disulfide; also known as Raluplate SPS (CAS 27206-35-5; Raschig company); Comparative example; SPV: 1-(3-sulfopropane base)-2-vinylpyridinium betaine; also known as Raluplate SPV (CAS 90552-35-5; Raschig Company); comparative example; MPS: 3-mercaptopropanesulfonic acid sodium salt; also known as Raluplate MPS (CAS 17636-10-1; Raschig); Comparative example; DTO: Dithiooxamide; Comparative example.

Specific compounds and their respective total concentrations are summarized in Table 1 below. Each passivation composition tested had a pH of about 2.

In each example, a silver-like zinc-iron layer (respectively for high iron content, Hiron-Zn/Fe and for low iron content, Protedur Plus, each a product of Atotech; for iron content, see Table 1 below) electroplated A plurality of u-shaped iron plate samples (base materials) were dipped as substrates in respective test passivation compositions having a temperature of about 22° C. for about 90 seconds. In the examples according to the invention, blackening was observed immediately.

Afterwards, the treated samples were dried and a post-dipping composition (acidic, containing trivalent chromium phosphate) and a sealant composition (basic, containing waxes and silicon-containing compounds) were applied. Subsequently, the blackening quality was evaluated visually; the corrosion resistance was evaluated according to ISO 9227. Table 1 : serial number %Fe blackening agent [mmol/L] Substances of metal ions [g/L] blackened quality Corrosion * [h] I-1 1.6 DPS 1.9 Cr(III) 3 to 4 ^## + ＜ 72 I-2 15 DPS 3.8 Zr(IV) 0.5 ++ ＜ 24 I-3 15 DPS 1.9 Ti(IV) 0.3 +++ 120 I-4 15 DPS ^# 1.9 to 8 ^## Cr(III) 3 to 4 +++ 480 II-1 15 ZPS 32.0 Cr(III) 3 to 4 ++ 240 C1 15 SPS 14.1 Cr(III) 3 to 4 - nd C2 15 SPV 22.0 Cr(III) 3 to 4 - nd C3 15 MPS 28.1 Cr(III) 3 to 4 - nd C4 15 DTO 41.6 Cr(III) 3 to 4 nd nd "*" means: time until maximum 5% white rust is observed, "^#" also tested on screws in barrel application, "^##" tested in compositions with various concentrations, "nd" means not determined, Typically due to no (sufficient) blackening, "+++" indicates excellent blackening; no visual defects are evident on all specimens, "++" indicates still acceptable blackening with only slight but still acceptable vision Defects; the entire sample is sufficiently black, "+" indicates no longer acceptable blackening, areas with significant visual defects and zinc iron layer, "-" indicates no or almost no blackening, visual defects and zinc iron large area

In all the examples according to the present invention (ie examples I-1, I-2, I-3, I-4 and II-1) a blackening of the zinc-iron alloy was obtained. Excellent results were obtained in Examples 1-3 and 1-4, with Example 1-4 providing these excellent results, even over a relatively broad concentration range for DPS and chromium ions.

In contrast, the alternative compounds (Comparative Examples C1 to C3) provide little or no blackening of the zinc-iron alloy. Example C4 revealed that DTO was not soluble at all and therefore was not available for testing and was found unsuitable. If blackening was not obtained, no further testing for corrosion resistance was performed, as blackening is a basic requirement.

In further comparative examples, the above test passivation compositions (in particular according to the invention) were tested using these substrates, but with a zinc (not zinc alloy) or zinc-nickel alloy layer thereon. In each of the other examples, blackening was not obtained (ie, evaluated as "-"). As a conclusion, the tested passivation compositions utilized in the method of the invention blacken zinc-iron alloys very specifically.

Claims (15)

A method for forming a black passivation layer on a zinc-iron alloy, the method comprising the following steps: (a) providing a substrate comprising the zinc-iron alloy, (b) providing a black passivation combination for depositing the black passivation layer on the zinc-iron alloy The composition comprises (i) one or more than one blackening agent selected from the group consisting of formula (I) and formula (II),

Wherein R ¹ and R ² are independently selected from the group consisting of hydrogen and C1 to C5 alkyl, R ³ is selected from the group consisting of sulfonic acid, carboxylic acid, alkyl carboxylic acid, phosphoric acid, salts and esters thereof, and n is 1, 2, 3, 4 or 5,

wherein R is selected from the group consisting of sulfonic acid, carboxylic acid, alkylcarboxylic acid, phosphoric acid, salts and esters thereof, and m is 1, 2, 3, ⁴ or 5, and (ii) one or more than one metal ion , the metal ion is selected from the group consisting of trivalent chromium, titanium and zirconium, and (c) making the substrate contact with the black passivation composition so that the black passivation layer is formed on the zinc-iron alloy. The method of claim 1, wherein the amount of iron in the zinc-iron alloy ranges from 0.1 wt% to 30 wt% based on the total weight of the zinc-iron alloy. The method according to claim 1 or 2, wherein the black passivation composition is acidic. The method according to claim 1 or 2, wherein in the black passivation composition, the one or more than one blackening agents have a total amount ranging from 0.2mmol/L to 100mmol/L based on the total volume of the black passivation composition concentration. The method of claim 1 or 2, wherein the black passivation composition comprises one or more of the formula (I) at a total concentration ranging from 0.4mmol/L to 25.0mmol/L based on the total volume of the black passivation composition More than one blackening agent. The method as in claim ¹ or ² , wherein R and R are independently selected from hydrogen, methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl and third butyl group of bases. The method according to claim 1 or 2, wherein R ³ includes at least sulfonic acid, its salt and/or ester. The method according to claim 1 or 2, wherein R ⁴ includes at least sulfonic acid, its salt and/or ester. The method of claim 1 or 2, wherein the one or more than one metal ion has a total concentration ranging from 0.1 g/L to 30 g/L based on the total volume of the black passivation composition and based on the mass of the free ions . The method according to claim 1 or 2, wherein the black passivation composition is substantially free of tungsten. The method according to claim 1 or 2, wherein the black passivation composition further comprises: (iii) one or more than one halide ion, and/or (iv) one or more than one carboxylic acid and/or its salt. The method according to claim 1 or 2, wherein in step (c), the black passivation composition has a temperature in the range of 10°C to 80°C. The method according to claim 1 or 2, wherein in step (c), the contacting is performed for a period of time ranging from 10 seconds to 200 seconds. A black passivation composition for depositing a black passivation layer on a zinc-iron alloy, the composition comprising (i) one or more than one blackening agent selected from the group consisting of formula (I) and formula (II) ,

Wherein R ¹ and R ² are independently selected from the group consisting of hydrogen and C1 to C5 alkyl, R ³ is selected from the group consisting of sulfonic acid, carboxylic acid, alkyl carboxylic acid, phosphoric acid, salts and esters thereof, and n is 1, 2, 3, 4 or 5,

wherein R is selected from the group consisting of sulfonic acid, carboxylic acid, alkylcarboxylic acid, phosphoric acid, salts and esters thereof, and m is 1, 2, 3, ⁴ or 5, and (ii) one or more than one metal ion , the metal ion is selected from the group consisting of trivalent chromium, titanium and zirconium, based on the total volume of the black passivation composition and the mass of these free ions, the total concentration range of the one or more than one metal ion is 0.1g /L to 30g/L, the limiting condition is that the black passivation composition is substantially free of nickel ions, cobalt ions and tungsten ions. A use of one or more than one black agent selected from the group consisting of formula (I) and formula (II),

Wherein R ¹ and R ² are independently selected from the group consisting of hydrogen and C1 to C5 alkyl, R ³ is selected from the group consisting of sulfonic acid, carboxylic acid, alkyl carboxylic acid, phosphoric acid, salts and esters thereof, and n is 1, 2, 3, 4 or 5,

Wherein R is selected from the group consisting of sulfonic acid, carboxylic acid, alkyl carboxylic acid, phosphoric acid, salts and esters thereof, and m is 1, 2, 3, ⁴ or 5, which is used to blacken zinc-iron alloys.