KR101998606B1 - trivalent chromate black corrosion-resistant enhancer agent for Zinc-Nickel plating and Surface treatment of Zinc-Nickel plating layer using the same - Google Patents

Abstract

The present invention relates to a surface treatment method for inhibiting corrosion by treating trivalent black chromate after plating zinc-nickel, and a black corrosion-resistant enhancer agent used therein. More specifically, the present invention relates to a black corrosion-resistant enhancer agent capable of obtaining corrosion resistance, stability of a solution, and a uniform black color, which can solve an environmental problem which conventional hexavalent black chromate has, and at the same time, has industrial ease.

Description

[0001] The present invention relates to a trivalent chromate-based black corrosion-resistance improving agent for zinc-nickel plating, and a surface treatment method of a zinc-nickel plating layer using the same.

The present invention relates to an environmentally friendly trivalent chromate-based black corrosion resistance improver which effectively improves corrosion resistance of a zinc-nickel plated product and does not contain hexavalent chromium, and a surface treatment method of a zinc-nickel plated layer using the same.

Conventionally, a surface treatment method has been used in which black chromate is treated with hexavalent chromium to improve corrosion resistance. However, since hexavalent chromium ions present in the process of use are known as highly toxic carcinogens, their use is strongly controlled worldwide, The price of the production of hexavalent chromium compounds and the disposal rate of the waste have risen. In recent years, environment-friendly technologies have been demanded such as the import regulations are strengthened and the imports are completely stopped. However, in some trivalent chromate treatment solutions, As a result of detection, hexavalent chromium of several ppm to several tens of ppm was detected.

As a conventional technique related to the chromate technique, a study on the characteristics of a chromate film and the effect of an additive on the ratio of hexavalent chromium and trivalent chromium to a galvanized steel sheet (J. Corros Sci. Soc. Of Korea Vo. 24, No 1., 1995. p46), and the relationship between the content of Ni and the corrosion resistance in zinc-nickel plating ( J. Materials processing tech ., 138 (2003) 63-66).

There is a known patent for an improved technique of change in corrosion resistance according to the concentration of trivalent chromium on zinc plating, and silica, cobalt, molybdate, phosphate and the like are widely known as materials for improving corrosion resistance.

Korean Patent No. 10-0490954 (Published on May 13, 2005)

In the present invention, by introducing Cr ³⁺ ions as an alternative compound of Cr ⁶⁺ in the chromate treatment process and introducing a specific organic compound as a black forming agent, the corrosion resistance of the zinc-nickel plating can be improved without using the environmentally harmful Cr ⁶⁺ The present invention has been completed. That is, the present invention provides a trivalent chromate-based black corrosion resistance improving agent for zinc-nickel plating having an optimum composition and composition ratio, and a method for treating a surface of a zinc-nickel plating layer using the same.

Of the present invention for solving the above problems of zinc-nickel-coated black trivalent chromate-based corrosion resistance-improving agent for the trivalent chromium (Cr ³⁺⁾ precursor, nitrate (NO ₃ ^-) precursor, a fluoride ion (F ^-) precursor, a cobalt ion (Co ²⁺ ) precursor, a reducing agent, a black forming agent and a solvent.

Further, in the surface treatment method of the zinc-nickel plated layer of the present invention, the surface of the zinc-nickel plated layer may be subjected to chromate treatment with the trivalent chromate-based black corrosion resistance improver for zinc-nickel plating.

It is another object of the present invention to provide a product comprising a zinc-nickel plated layer which has been subjected to a chromate treatment by the surface treatment method.

The black corrosion resistance improver for zinc-nickel plating of the present invention can greatly improve the corrosion resistance of zinc-nickel plating without containing environmentally harmful Cr ⁶⁺ , and is excellent in stability even in a wide pH range, The black coloring property is excellent.

Fig. 1 is a graph showing a test result of corrosion resistance measurement according to the concentration of black forming agent in the black corrosion resistance improving agent.
2 is a graph showing a test result of corrosion resistance measurement according to the Cr ³⁺ concentration in the black corrosion resistance improver.
3 is a graph showing a test result of corrosion resistance measurement according to the NO ³ concentration in the black corrosion resistance improving agent.
4 is a graph showing a test result of corrosion resistance measurement according to the concentration of Co ²⁺ in the black corrosion resistance improver.
5 is a graph showing a test result of corrosion resistance measurement according to the F ^- concentration in the black corrosion resistance improver.
Fig. 6 is a graph showing a test result of the corrosion resistance measurement according to the pH of the black corrosion resistance improver.

Hereinafter, the present invention will be described in detail.

The present invention relates to a surface treatment method of a zinc-nickel plated layer for chromating a surface of a zinc-nickel plating.

More specifically, the first step is to perform the cleaning of the zinc-nickel-plated article 1 to 3 times; A second step of immersing the washed article in a black corrosion resistance improving agent at room temperature for 30 seconds to 2 minutes to perform a chromate treatment; And 3) washing the chromated product two to three times.

The chromate treatment uses a trivalent chromate-based black corrosion resistance improver (hereinafter referred to as "black corrosion resistance improver").

The black corrosion resistance improver includes a trivalent chromium (Cr ³⁺ ) precursor, a fluorine ion (F ^- ) precursor, a cobalt ion (Co ²⁺ ) precursor, a reducing agent, a black forming agent and a solvent.

It may further comprise a nitrate (NO ₃ ^- ) precursor.

The black coloring agent in the black corrosion resistance improving agent composition is a compound having functional groups of an organic substance at the same time having both an amine group and a carboxylic acid group and plays a role of securing pH stability in the corrosion resistance improving agent and preventing deterioration of corrosion resistance, And organic compounds represented by the following general formula (2).

[Chemical Formula 1]

In formula (1), R ₁ is a straight-chain alkyl group of 1 to 16 carbon atoms or a straight-chain alkyl group of 1 to 16 carbon atoms containing -OH, -CONH-, -NH ₂ or -COOH as a functional group.

(2)

X is a carbon atom or a nitrogen atom, R ₂ is a linear alkyl group having 1 to 16 carbon atoms, a phenyl group or a group represented by -OH, -CONH-, -NH ₂ , -COOH, -F, -Cl, -OCH ₃ Or a linear alkyl group having 1 to 16 carbon atoms containing -NO ₃ as a functional group.

As the organic compound represented by the above-mentioned formula (1), specific examples of the black forming agent include asparagin, aspartic acid, glycine, alanine, 3-aminobutanoic acid 2-aminobutyric acid, glutamic acid, cysteine, valine, hystidine, methionine, tyrosine, tryptophan, ), Leucine, isoleucine, glutamine, lysine, arginine, serine, praline and threonine, among which one or more of Two or more of them may be used as black formers.

Specific examples of the black forming agent as the organic compound represented by Formula 2 include 4-amino benzoic acid, 2-amino-3-methoxybenzoic acid, 4-amino-2-fluorobenzoic acid, 4- (2-aminoethyl) benzoic acid, 4- 3-amino adipic acid, p-aminohippuric acid, 4-amino-3-hydroxybenzoic acid, 4-amino- Amino-2-hydroxybutyric acid, 3-amino-2-napthoic acid, 2-aminonicotinic acid, 2-aminoterephthalic acid, 2-aminoterephthalic acid, anthranilic acid, 3,4-diaminobenzoic acid and 2-aminonicotinic acid, among which 1 Or two or more species may be used as a black forming agent.

The black forming agent is preferably used in a concentration of 0.1 to 15 g / L, preferably 0.5 to 10.0 g / L, more preferably 2.0 to 8.0 g / L in the black corrosion resistance improving agent, the function as a pH buffer is insufficient and defective appearance of the surface-treated zinc-nickel plating may occur, and when it exceeds 15.0 g / L, the corrosion resistance may be significantly deteriorated.

Next, the trivalent chromium precursor of the black corrosion-resistance enhancer composition may include at least one selected from KCrSO ₄ and Cr (NO ₃ ) ₃ .

The amount of the trivalent chromium precursor used is preferably 1.0 to 9.0 g / L, more preferably 3.0 to 8.0 g / L, so that the Cr ³⁺ concentration in the black corrosion resistance improver is 0.5 to 10.0 g / It is good to do. At this time, when the black corrosion resistance improver Cr ³⁺ concentration is less than 0.5 g / L, the corrosion resistance is too low and the chromate treatment effect may not be obtained. When the concentration exceeds 10.0 g / L, precipitates are formed in the corrosion resistance improving agent, It is not economical.

Next, the cobalt ion precursor of the black corrosion resistance improver composition serves to improve the appearance uniformity and corrosion resistance of the chromated surface, and may include at least one selected from CoCl ₂ and Co (NO ₃ ) ₂ .

The amount of the cobalt ion precursor used is such that the concentration of Co ²⁺ in the black corrosion resistance improver is 0.5 to 15.0 g / L, preferably 1.0 to 10.0 g / L, more preferably 2.5 to 9 g / L good. If the concentration of Co ^{2+ in the} black corrosion resistance improver is less than 0.5 g / L, corrosion resistance is deteriorated. If it is used in excess of 15.0 g / L, corrosion resistance may be decreased and appearance uniformity may be deteriorated.

Next, the fluorine ion precursor in the black corrosion-resistance enhancer composition may serve as a black forming auxiliary and increase the blackness, and may include at least one selected from NaF and KF.

The amount of the fluorine ion precursor used is such that the F ^- concentration in the black corrosion resistance improver is 0.001 to 2.0 g / L, preferably 0.05 to 1.0 g / L, more preferably 1.0 to 0.75 g / L good. At this time, the black corrosion resistance-improving agent within the ^F-fluoride so that the concentration ^- the concentration is 0.001g / L under blackness no effect of improvement, the use in excess of 2.0g / L, F in the range, so the corrosion resistance can be reduced It is preferable to use an ion precursor.

Next, the reducing agent serves to reduce residual hexavalent chromium ions in the black corrosion resistance improving agent, and may be an alcohol or a glycol compound. Specific examples thereof include methanol, ethanol, propanol, isopropane ethanol, ethylene glycol , Ethylene glycol disodium salt, polyethylene glycol having a weight average molecular weight of 200 to 6,000, lauryl alcohol, and stearyl alcohol.

The use amount of the reducing agent is preferably 0.001 to 5.0 ml / L, preferably 0.01 to 3.0 ml / L, more preferably 0.05 to 2.5 g / L in the black corrosion resistance improving agent. If the concentration of the reducing agent in the black corrosion resistance improving agent is less than 0.001 g / L, hexavalent chromium can be detected, and if it is used in an amount exceeding 5.0 ml / L, corrosion resistance and appearance change may be adversely affected. .

Next, in the black corrosion resistance improver of the present invention, Cr (NO ₃ ) ₃ is used as a trivalent chromium precursor and Co (NO ₃ ) ₂ is used as a cobalt ion precursor so that NO ₃ ^- ions are introduced. NO ₃ ^- ions may be introduced, or a nitrate (NO ₃ ^- ) precursor may additionally be used in the case of using a trivalent chromium precursor and a cobalt ion precursor that do not contain NO ₃ ^- ions. The nitrate precursor may be at least one selected from the group consisting of HNO ₃ , NaNO ₃ and KNO _3. The concentration of nitrate ions (NO ₃ ^- ) in the black corrosion resistance enhancer is 0.5 to 15.0 g / L, preferably 1.0 to 10.0 g / L, and more preferably 4 to 10.0 g / L. At this time, if the NO ₃ ^- concentration is less than 0.5 g / L, the corrosion resistance may be somewhat lowered. If the NO ₃ ^- concentration is more than 15.0 g / L, there is no additional corrosion resistance improvement effect.

The black corrosion resistance improver of the present invention having the above composition and composition ratio preferably has a pH of 1.0 to 4.0, preferably a pH of 1.4 to 3.5, more preferably a pH of 1.6 to 3.0. When the pH is less than 1.0, Redness may occur due to excessive etching of the zinc-zinc nickel layer. If the pH exceeds 4.0, there may be a problem that uniform black is not formed and corrosion resistance is lowered.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples are provided to aid understanding of the present invention, and the scope of the present invention should not be narrowly interpreted by the following examples.

[Example]

Preparation Example: Preparation of Zinc-Nickel Plating Specimen

The steel specimens were subjected to electrolytic degreasing for 5 minutes. Ni (99.9% by weight) was used as a positive electrode in the zinc-nickel plating and XNP-8000 (trade name: Weight%) was used to prepare a zinc-nickel plated specimen by plating to a plating thickness of 8um (+/- 2um).

Next, the zinc-nickel plated specimen was washed twice.

Example 1: Preparation of trivalent chromate-based black corrosion-resistance enhancer and chromate treatment

(1) The precursor of trivalent chromium (Cr ³⁺ ) in the DI water is 60 g / L of KCrSO ₄ · 12H ₂ O as a reagent grade, 10 g / L of NaNO ₃ (Daejeong Chemical Co.) as a precursor of nitrate (NO ₃ ^- 15 g / L of NaF as a precursor (F ^- ), 15 g / L of a cobalt ion (Co ²⁺ ) precursor Co (NO ₃ ) ₂ (Kanto Co.), 5 ml / L of ethylene glycol as a reducing agent and asparagin 0.02 M (= 2.64 g / L) were mixed and stirred for 60 minutes. Next, it was adjusted to pH 2.0 to prepare a black corrosion resistance improving agent.

(2) Next, the zinc-nickel plated specimen prepared in the preparation example was immersed in the black corrosion resistance improver prepared above at room temperature (20 to 35 DEG C) for 50 seconds to perform chromate treatment, and then immersed in each other water bath , Followed by washing with water twice while stirring with air, followed by coating with a coating agent. At this time, a 40% dilution solution of SC-500 (Jis-Chemtech, Korea) was used as a coating agent.

Next, this was dried at 80 ° C for 15 minutes to prepare a surface-treated specimen of the final zinc-nickel plated layer.

division Kinds Precursor concentration Ion concentration Cr ³⁺ precursor KCrSO ₄ · 12H ₂ O 60g / L 6.25 g / L NO ₃ ^- precursor NaNO ₃ 10 g / L 7.29 g / L F ^- precursor NaF 0.1 g / L 0.05 g / L Co ²⁺ precursor Co (NO _{3) 2} 15g / L 3.04 g / L reducing agent Ethylene glycol 5ml / L - Black forming agent Asparagine 2.64 g / L -

Examples 1-2 to 1-14 and Comparative Example 1-1

The specimens were subjected to the surface treatment of the zinc-nickel plated layer in the same manner as in Example 1 except that the black forming agents among the black corrosion resistance improving agent components were prepared as shown in Table 2 below, The plating layer was surface-treated, and the results of the surface-treated appearance measurement are shown in Table 2 below.

division Black builder type Exterior Example 1-1 Asparagine Uniform and glossy black Examples 1-2 Aspartic acid Uniform and glossy black Example 1-3 L-hystidine Uniform and glossy black Examples 1-4 Glycine Uniform and glossy black Examples 1-5 L-Valine Uniform and glossy black Examples 1-6 Methionine Uniform and glossy black Examples 1-7 Alanine Uniform and glossy black Examples 1-8 Tyrosine Uniform and glossy black Examples 1-9 tryptophan Uniform and glossy black Example 1-10 L-Cysteine Uniform and glossy black Example 1-11 4-amino benzoic acid Uniform and glossy black Examples 1-12 2-aminonicotinic acid Uniform and glossy black Examples 1-13 Malonic acid Uniform and glossy black Examples 1-14 Malic acid Uniform and glossy black Comparative Example 1-1 Do not use black formers No black formation.

In the case of Examples 1-1 to 1-14, black chromate is well formed. However, in the case of Comparative Example 1-1 in which an organic material type black forming agent was not used, it was confirmed that black was not formed.

Examples 1-15 to 1-22

The black corrosion resistance improver was prepared in the same manner as in Example 1 except that the black corrosion resistance improver was prepared by varying the concentration of asparagine, which is a black forming agent, as shown in Table 3 below, and the zinc-nickel plating layer was surface-treated .

Experimental Example 1-1: Measurement of corrosion resistance change according to the concentration of black forming agent

The corrosion resistance of each of the zinc-nickel plated specimens of Examples 1-15 to 1-22 subjected to black chromate treatment (surface treatment) was measured, and the results are shown in Table 3 and FIG.

At this time, the corrosion occurrence time was measured according to KS D 9502 method.

division Concentration (g / L) Whitehead occurrence time (Hrs) Examples 1-15 Black forming agent
(Asparagine) 2 164 Examples 1-16 4 198 Examples 1-17 6 194 Example 1-18 8 190 Example 1-19 10 186 Examples 1-20 12 185 Examples 1-21 14 155 Examples 1-22 16 146

As a result of the corrosion resistance measurement of Table 3, it can be seen that the corrosion resistance tends to drop sharply when the use concentration of the black forming agent exceeds 15 g / L.

EXPERIMENTAL EXAMPLE 1-2: Measurement of corrosion resistance change 2

Each of the zinc-nickel plated specimens of Examples 1-2, 1-3, 1-6, 1-11, and 1-12 subjected to the black chromate treatment (surface treatment) was subjected to a salt spray test by the KS D 9502 method The results are shown in Table 4. [Table 4] < tb > < TABLE > At this time, if the incidence of white rust is less than 5% for 200 hours, it is acceptable. If the red rust occurrence rate is less than 5% for 1000 hours, it is acceptable.

division Less than 5% (200 hours, hrs) Less than 5% red (1000 hours, hrs) Examples 1-2 pass pass Example 1-3 pass pass Examples 1-6 pass pass Example 1-11 pass pass Examples 1-12 pass pass

Examples 2-1 to 2-7

A black corrosion resistance enhancer was prepared in the same manner as in Example 1-1 except that the amount of KCrSO ₄ .12H ₂ O precursor (Cr ³⁺ ) was adjusted so that Cr ^{3 +} Concentration, respectively, and then zinc-nickel plating layer was surface-treated using the same.

Experimental Example 2: Cr ³⁺  Measurement of corrosion resistance change according to concentration

The corrosion resistance of each of the zinc-nickel plated specimens of Examples 2-1 to 2-7 subjected to black chromate treatment (surface treatment) was measured, and the results are shown in Table 5 and FIG. At this time, the corrosion resistance was measured in the same manner as in Experimental Example 1.

division Concentration (g / L) Whitehead occurrence time (Hrs) Example 2-1 Black corrosion resistance
Within the enhancer
Cr ³⁺ concentration 3 116 Example 2-2 4 153 Example 2-3 5 151 Examples 2-4 6 194 Example 2-5 7 192 Examples 2-6 8 190 Examples 2-7 9 189

As shown in Table 5 and FIG. 2, corrosion resistance was excellent in proportion to the increase of the Cr ³⁺ concentration in the corrosion resistance improver. However, there is a problem that precipitates are generated from a concentration of Cr ³⁺ concentration exceeding 10 g / L.

Examples 3-1 to 3-8

A black corrosion resistance improving agent was prepared in the same manner as in Example 1-1 except that the amount of NaNO _{3 as a} precursor of nitrate salt (NO ₃ ^- ) was controlled so that a black corrosion resistance improving agent having NO ₃ ^- Respectively. Then, the zinc-nickel plated layer was surface-treated.

Experimental Example 3: NO ₃ ^- Measurement of corrosion resistance change according to concentration

The corrosion resistance of each of the zinc-nickel plated specimens of Examples 3-1 to 3-8 subjected to black chromate treatment (surface treatment) was measured, and the results are shown in Table 6 and FIG. At this time, the corrosion resistance was measured in the same manner as in Experimental Example 1. The outer appearance was evaluated based on gloss and uniform color with a black appearance.

division Concentration (g / L) Whitehead occurrence time (Hrs) Exterior Example 3-1 Black corrosion resistance
Within the enhancer
NO ₃ ^- Concentration 2 116 usually Example 3-2 4 142 Great Example 3-3 6 149 Very good Example 3-4 8 186 Very good Example 3-5 10 183 Very good Examples 3-6 12 181 Very good Examples 3-7 14 179 Very good Examples 3-8 16 178 Some bad

As shown in Table 6 and FIG. 3, the corrosion resistance was excellent in proportion to the increase of NO ₃ ^- concentration in the corrosion resistance improver. However, NO ₃ ^- concentration of 8 ~ 10g / L range of the decrease is somewhat corrosion starting concentration by the improved corrosion resistance effect most excellent, and more than 10g / L, and showed results without the corrosion resistance increases, NO ₃ ^- concentration of 15g / L, the appearance of the surface-treated specimen was defective.

Examples 4-1 to 4-7

The black corrosion resistance improver was prepared in the same manner as in Example 1-1 except that the amount of Co (NO ₃ ) ₂ , which is a precursor of cobalt ion (Co ²⁺ ), was controlled so that Co ²⁺ , Respectively, and then zinc-nickel plating layer was surface-treated using the same.

Experimental Example 4: Co ²⁺ Measurement of corrosion resistance change according to concentration

The corrosion resistance of each of the zinc-nickel plated specimens of Examples 4-1 to 4-7 subjected to black chromate treatment (surface treatment) was measured, and the results are shown in Table 7 and FIG. At this time, the corrosion resistance was measured in the same manner as in Experimental Example 1.

division Concentration (g / L) Whitehead occurrence time (Hrs) Example 4-1 Black corrosion resistance
Within the enhancer
Co ²⁺ concentration One 109 Example 4-2 3 199 Example 4-3 5 197 Example 4-4 7 193 Example 4-5 9 188 Examples 4-6 11 184 Examples 4-7 13 142

As shown in Table 7 and FIG. 4, when the concentration of Co ^{2+ in the} corrosion resistance improver is in the range of 1 g / L to 3 g / L, the effect of improving the corrosion resistance tends to increase sharply and is in the range of 3 to 11 g / L, , It showed uniform corrosion resistance as a whole in the range of 10 g / L to 10 g / L. However, there was a problem that the corrosion resistance was rapidly decreased from the concentration exceeding 11 g / L.

Examples 5-1 to 5-7

It was prepared in a black corrosion resistance-enhancing agent in the same manner as Example 1-1, a fluorine ion (F ^-) to adjust the amount of NaF as a precursor to, to within a black corrosion-resistant improver F as shown in Table 8 ^- black corrosion resistance-improving agent having a concentration The zinc-nickel plated layer was surface-treated using the zinc-nickel plated layer.

Experimental Example 5: F ^- Measurement of corrosion resistance change according to concentration

The corrosion resistance of each of the zinc-nickel plated specimens of Examples 5-1 to 5-7 subjected to black chromate treatment (surface treatment) was measured, and the results are shown in Table 8 and FIG. At this time, the corrosion resistance was measured in the same manner as in Experimental Example 1.

division Concentration (g / L) Whitehead occurrence time (Hrs) Example 5-1 Black corrosion resistance
Within the enhancer
F ^- Concentration 0.025 147 Example 5-2 0.05 155 Example 5-3 0.1 181 Examples 5-4 0.15 179 Example 5-5 0.2 154 Examples 5-6 0.5 97 Examples 5-7 One 96

Referring to Table 8 and FIG. 5, the corrosion resistance effect is increased in proportion to the increase of the F ^- concentration in the corrosion resistance improver, and the corrosion resistance is maximized in the range of 0.1 to 0.15 g / L. There is a tendency that the corrosion resistance tends to deteriorate from a concentration exceeding 0.15 g / L, but there is a problem that the corrosion resistance decreases rapidly from a concentration exceeding 0.3 g / L.

Examples 6-1 to 6-7

The black corrosion resistance improver was prepared in the same manner as in Example 1-1 except that the pH of the black corrosion resistance improver was adjusted as shown in Table 9, and the zinc-nickel plating layer was surface-treated using the same.

Experimental Example 6-1: Measurement of corrosion resistance change according to pH

The corrosion resistance of each of the zinc-nickel plated specimens of Examples 6-1 to 6-7 subjected to the black chromate treatment (surface treatment) was measured, and the results are shown in Table 9 and FIG. At this time, the corrosion resistance was measured in the same manner as in Experimental Example 1.

division pH Whitehead occurrence time (Hrs) Example 6-1 Black corrosion resistance
Enhancer
pH 1.0 96 Example 6-2 1.4 107 Example 6-3 1.8 186 Example 6-4 2.2 183 Examples 6-5 2.6 179 Examples 6-6 3.0 158 Examples 6-7 4.0 137

In the case of trivalent black chromate treatment, pH control is very important. Referring to Table 9 and FIG. 6, the corrosion resistance is maximized in the range of pH 1.8 to 2.2, and the corrosion resistance rapidly decreases from the concentration exceeding pH 3.0.

Although not shown in Table 9 and FIG. 6, when the pH is higher than 4.5, uniform black is not formed and corrosion resistance is very low.

Experimental Example 6-2: Measurement of etch rate and corrosion resistance according to pH

The pH of the black corrosion-resistance enhancer prepared in Example 1-1 was adjusted as shown in Table 10, and each of them was subjected to a salt spray test by the KS D 9502 method to measure the etch rate and the occurrence time of white rust and red rust , And the results are shown in Table 10 below.

Black corrosion resistance
The pH of the enhancer Etch
(um / min) Whitehead occurrence time
(Less than 5%) Red rush hour
(Less than 5%) pH = 0.5 7.5 12 hours (hrs) 78 hours pH = 2.0 1.42 230 hours 1100 hours pH = 4.5 0.32 36 hours 400 hours

The results of the measurement of the above Table 10 confirm that there is a problem that the corrosion resistance is greatly lowered at pH 0.5 and pH 4.5 as compared with pH 2.0.

Examples 7-1 to 7-4 and Comparative Example 7-1

(1) The precursor of trivalent chromium (Cr ³⁺ ) in the DI water is 60 g / L of KCrSO ₄ · 12H ₂ O as a reagent grade, 10 g / L of NaNO ₃ (Daejeong Chemical Co.) as a precursor of nitrate (NO ₃ ^- 15 g / L of NaF as a precursor (F ^- ), 15 g / L of cobalt ion (Co ²⁺ ) precursor Co (NO ₃ ) ₂ (Kanto Co.), 5 ml / L of methanol as a reducing agent and L-histidine -hystidine) were mixed and stirred for 60 minutes. Next, it was adjusted to pH 2.0 to prepare a black corrosion resistance improving agent.

(2) Next, the zinc-nickel plated layer was surface-treated in the same manner as in Example 1-1 to perform Example 7-1.

Examples 7-2 to 7-4 and Comparative Example 7-1 were conducted as shown in Table 9 below.

Experimental Example 7: Cr ⁶⁺  Measurement of detection

The surface-treated zinc-nickel plated specimens of Examples 7-1 to 7-4 and Comparative Example 7-1 were subjected to the detection test of hexavalent chrome according to the EPA 3060A method, and the results are shown in Table 11 below.

division Comparative Example 7-1 Example 7-1 Example 7-2 Example 7-3 Example 7-4 Type of reducing agent No reducing agent MeOH EtOH IPA
(isopropyl alcohol) Ethylene glycol Cr ⁶⁺ 4 ppm Not detected Not detected Not detected Not detected

From the results of the experiment of Table 11, it was confirmed that hexavalent chromium was reduced when an alcohol or glycol system was added as a reducing agent.

Experimental Example 8: Comparative test of pH stability of black corrosion inhibitor according to black forming agent

Each of the black corrosion resistance enhancers prepared in Examples 1-3, 1-4, 1-13, and 1-14 was adjusted to pH 2.2, and then allowed to stand in a dark room at room temperature for 7 days to change the pH The stability of the black corrosion-resistance enhancer was measured by confirming the results, and the results are shown in Table 12 below.

division Black forming agent Initial pH 7 days elapsed pH Example 1-3 L-hystidine 2.2 1.9 Examples 1-4 Glycine 2.2 2.1 Examples 1-13 Malonic acid 2.2 0.4 Examples 1-14 Malic acid 2.2 0.6

The pH buffering effect of the zinc-nickel plated specimens surface-treated in the same manner as in Example 1-1 was measured using the black corrosion resistance improvers of Examples 1-4 and 1-13, The results are shown in Table 13 below. pH buffering was measured by surface treatment (chromate treatment) with zinc corrosion-resistance improving agent of 10 dm ² (1 cm is 0.1 dm ² ) on zinc-nickel plated specimen [10 cm * 10 cm * both sides].

division Black forming agent Initial pH PH after 100 dm ² treatment Examples 1-4 Glycine 2.2 2.4 Examples 1-13 Malonic acid 2.2 4.0

In the measurement results of the pH changes in Tables 12 and 13, the pH stability of Examples 1-13 (malonic acid) and Example 1-14 (malic acid) in which amine groups are not present as functional groups is not very good, It was confirmed that the pH buffer and pH stability of Example 1-3 (L-histidine) and Example 1-4 (glycine) introduced as a black forming agent having an amine group were significantly improved.

Experimental Example 9: Measurement of blackness according to addition of fluorine ion

In Example 1-3, the blackness according to the presence or absence of NaF was compared and the model name Minolta CM-580D was used as the blackness measuring device. The results are shown in Table 14 below.

division Not added Addition (Example 1-3) Blackness (L) 20 8

It can be seen from Table 14 that the blackness is further improved when F- ion is present.

Example 8

40 g / L of Cr (NO ₃ ) ₃ , ₁₂ g / L of Co (NO ₃ ) ₂ , ₁ g / L of methionine as a black coloring agent, 0.02 g / L of NaF and 3 ml / After stirring for 60 minutes, the pH was adjusted to 2.2, and then zinc-chrome plated specimens were treated with chromate according to the standard procedure in the same manner as in Example 1-1.

The pH change, the detection of hexavalent chromium, the degree of blackness and the spraying of salt water were carried out in the same manner as in the experimental example, and the results are shown in Table 15 below.

division PH after 7 days Hexavalent chromium detection Blackness White Chung 5%
(200 hrs) Red 5%
(1,000 hrs) Example 8 1.8 No detection 11 pass pass

As a result of the measurement of the above Table 15, in the case of Example 8 in which no separate nitrate precursor was used, NO ₃ ^- was generated from the chromium precursor and the cobalt precursor as compared with Example 1-1 and Example 1-6 It was confirmed that excellent corrosion resistance, blackness and pH stability effects were obtained as in Example 1-1 and / or Example 1-6.

Claims (12)

delete delete delete delete delete delete delete delete delete delete (Cr ³⁺ ) precursor, a fluorine ion (F ^- ) precursor, a cobalt ion (Co ²⁺ ) precursor, a reducing agent, a black forming agent, a nitrate (NO ₃ ^- ) precursor,
It said third and chromium precursor comprises KCrSO ₄ and Cr (NO _{3) 3} 1 or more kinds selected from,
The black formers may be selected from the group consisting of asparagin, aspartic acid, alanine, 3-aminobutanoic acid, 2-aminobutyric acid, But are not limited to, glutamic acid, cysteine, valine, hystidine, methionine, tyrosine, tryptophan, leucine, isoleucine, Glutamine, lysine, arginine, serine, praline, threonine, 4-aminobenzoic acid, 2-amino-3- Amino-3-methoxybenzoic acid, 4- (2-aminoethyl) benzoic acid, 4-amino-2-fluorobenzoic acid, 2-fluorobenzoic acid, 3-amino adipic acid, p-aminohippuric acid, 4-amino-3- hydroxybenzoic acid), 4-amino-2 2-hydroxybutyric acid, 3-amino-2-naphthoic acid, 2-aminonicotinic acid, 2-aminonicotinic acid, (1) selected from the group consisting of 2-aminoterephthalic acid, anthranilic acid, 3,4-diaminobenzoic acid and 2-aminonicotinic acid. More than species,
Wherein the cobalt ion precursor comprises at least one selected from CoCl ₂ and Co (NO ₃ ) ₂ ,
The fluorine ion precursor includes at least one selected from NaF and KF,
Wherein the nitrate (NO ₃ ^- ) precursor comprises at least one selected from HNO ₃ , NaNO ₃ and KNO ₃ ,
The reducing agent may be at least one selected from the group consisting of methanol, ethanol, propanol, isopropanol ethanol, ethylene glycol, ethylene glycol disodium salt, polyethylene glycol having a weight average molecular weight of 200 to 6,000, lauryl alcohol and stearyl alcohol / RTI >
The corrosion resistance improver has a Cr ³⁺ concentration of 4.0 to 8.0 g / L, a NO ₃ ^- concentration of 4.0 to 14.0 g / L, a Co ²⁺ concentration of 3.0 to 10.0 g / L, an F ^- concentration of 0.001 to 0.3 g / L, a reducing agent of 0.001 to 5.0 ml / L, 2.0 to 12 g / L of the black forming agent,
Wherein the black corrosion resistance improver is at a pH of 1.4 to 3.0, and is a trivalent chromate-type black corrosion inhibitor for zinc-nickel plating.
A method for surface treatment of a zinc-nickel plated layer, characterized in that the surface of the zinc-nickel plated layer is subjected to a chromate treatment with the trivalent chromate-based black corrosion-resistance improving agent of claim 11.

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