JPH05475B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD OF THE INVENTION The present invention relates to an electrolytic zinc-nickel alloy plating bath. BACKGROUND TECHNOLOGY AND PROBLEMS Zinc plating has a strong corrosion-preventing effect on iron substrates, and is widely applied to everything from small parts such as bolts and nuts to large materials such as steel plates and wire rods. However, in recent years, due to the use of snow-melting salts, etc., the number of substances that have a corrosion-promoting effect has increased in the environment, and as a result, improvements in the corrosion performance of various products are required, and the development of a matting film with even better corrosion resistance is desired. There is. Zinc-nickel alloy plating films are known to have better corrosion performance than zinc plating films, and plating baths with various compositions have been researched.
For example, plating baths shown in Japanese Patent Publication No. 12434/1982 and Japanese Patent Publication No. 58313/1982 are known. however,
In general, in alloy plating by electroplating, it is known that the alloy composition of the deposited film differs depending on the current density. It is difficult to obtain a plated film with a uniform alloy composition because there are parts with different values. In particular, zinc-nickel alloy plating has the disadvantage that low current density areas tend to form a film rich in nickel, and only those areas exhibit a black appearance. In order to improve these defects, if a high current is applied to the plated product, an extremely high current will flow in areas with high current density such as the corners of the plated product, resulting in a rough surface called burnt. A licking film is formed and the appearance of the coated product is impaired. Furthermore, if parts with significantly different alloy compositions occur on the plated product, local corrosion will be accelerated, leading to the problem that the corrosion protection performance for the plated product will be insufficient. For these reasons, in conventional electrolytic zinc-nickel alloy plating baths, in order to obtain plated products with excellent corrosion protection and good appearance, the applicable current density range is severely limited, and The accessories are limited to those that do not cause a large current density distribution in terms of shape, size, etc. Furthermore, since the current value must be strictly controlled, there is also the drawback that the work is complicated. For this reason, zinc-nickel alloy plating has not been fully industrialized at present, although it is a tough coating with excellent anticorrosion properties. Means for Solving the Problems In view of the above-mentioned current situation, the inventor of the present invention aimed to improve the appearance of the electrolytic zinc-nickel alloy with excellent uniformity in a wide range of current density in order to expand the range of applications of electrolytic zinc-nickel alloy plating. We have been conducting extensive research to find a plating bath that can form a plating film. As a result, by using a specific anionic surfactant as an additive in a zinc-nickel alloy plating bath containing zinc chloride, nickel chloride, and ammonium chloride as main ingredients, good appearance can be achieved over a wide range of current density. It has been discovered that a plated film exhibiting the following properties can be obtained, and the present invention has now been completed. That is, the present invention provides: (i) zinc chloride (as Zn ²⁺ ) 12.5 to 90 g/, (ii) nickel chloride (as Ni ²⁺ ) 5 to 60 g/, (iii) ammonium chloride (as NH ₄ ⁺ ) 5 ~120
g/, and (iv) Sodium oleate, sodium octylphenoxyethoxyethyl sulfonate, sodium monolaurylglyceryl sulfate, sodium dioctyl sulfosuccinate, funnel oil, 1,5
- Contains 0.2 to 20 g of at least one anionic surfactant selected from sodium diisopropyl-7-naphthalene sulfonate and sodium polyoxyethylene-β-naphthol sulfate, and Zn ²⁺ /Ni ²⁺ (weight ratio) = 0.2 to 2.5, and the electrolytic zinc-nickel alloy plating bath is characterized in that the pH is adjusted to 4.7 to 7.0 with ammonia water. In the electrolytic zinc-nickel alloy plating bath of the present invention, a plating bath containing zinc chloride, nickel chloride, and ammonium chloride as main ingredients is used as a basic bath.
In the plating bath, the metal concentration is 12.5 to 12.5 as Zn ²⁺
90g/, 5 to 60g/ as Ni ²⁺ ,
It is appropriate that the Zn ²⁺ /Ni ²⁺ (weight ratio) is between 0.2 and 2.5; if the metal concentration is outside this range, it will be difficult to obtain a plated film with a good appearance. In addition, the NH ₄ ⁺ concentration must be 5 to 120 to obtain a good plating film.
It is appropriate to set it to about g/g. In the plating bath of the present invention, sodium oleate,
Sodium octylphenoxyethoxyethylsulfonate, sodium monolaurylglyceryl sulfate, sodium dioctylsulfosuccinate, funnel oil, sodium 1,5-diisopropyl-7-naphthalenesulfonate, and polyoxyethylene-
At least one anionic surfactant selected from sodium β-naphthol sulfate is used. By using these anionic surfactants,
A highly corrosion-resistant film with dense, uniform crystals that does not form a black film can be obtained over a wide current density range.
The amount of anionic surfactant added is 0.2 to 20g/
It is appropriate to If the amount added is less than 0.2g/, a sufficient addition effect cannot be obtained;
If the amount added is more than 100%, the addition effect will not be further improved, and the amount of plating solution pumped out will increase due to increased bubbling, which will increase the burden on wastewater treatment, which is not preferable. If necessary, aromatic aldehydes, aromatic ketones, etc. can be added to the plating bath of the present invention in order to improve the gloss, leveling, etc. of the plating film. Specific examples of these include benzalacetone, anisaldehyde, vanillin, cinnamaldehyde, veratraldehyde, etc., and by adding about 0.01 to 2 g/g, a plated film with specular luster can be obtained. In addition, phthalic acid, benzoic acid, quinaldic acid, naphthalene-1,2-dicarboxylic acid, and acetic acid are added for the purpose of improving the flexibility of the plating film and preventing the formation of a black film on microcurrent areas of about ^0.3 A/dm 2 or less. , propionic acid, oxalic acid, and carboxylic acid compounds that are salts thereof, tartaric acid,
salicylic acid, m-oxycinnamic acid, 1-oxy-
2-naphthoic acid, 2-oxy-1-naphthoic acid,
Maleic acid, oxycarboxylic acid compounds that are their salts, glutamic acid, tryptophan, glycine, phenylalanine, histidine, and amino acid compounds that are their salts, etc., at 0.005 to 10
It is also possible to add approximately g/g. In the plating bath of the present invention, ammonia water is used to
4.7 to 7.0, and perform plating treatment at a bath temperature of about 30 to 45℃, average cathode current density of about 0.5 to 8A/ ^dm2 , and agitation using air agitation, mechanical agitation, etc., to achieve a good appearance. It is possible to obtain a zinc-nickel alloy plating film having the following characteristics and excellent corrosion resistance. Effects of the Invention By using the plating bath of the present invention, it is possible to form a zinc-nickel alloy plating film that has a good appearance in a wide range of current density areas and has excellent anticorrosion performance. Therefore, it is possible to form a plating film that has a uniform appearance over the entire part and has excellent corrosion resistance even on a plated product with a complicated shape where parts with large current densities are likely to differ. Therefore, it has become possible to apply zinc-nickel plating to coated products of various shapes and sizes, and it has become easier to control the current value during plating processing, greatly increasing the practicality of electrolytic zinc-nickel plating. Improve your skills. Examples Hereinafter, the present invention will be explained in detail with reference to Examples. Example 1 A Hull Cell plating test was conducted using a Hull Cell tester using a plating bath having the following composition. Zinc chloride 100g/Nickel chloride hexahydrate 130g/Ammonium chloride 200g/Sodium oleate 0.3g/Adjusted to pH5.7 with 25% ammonia water The plating conditions for the Hull cell test are as shown below. Test liquid volume 267ml Stirring Air stirred cathode Polished steel plate anode Zinc plate plating temperature 35℃ Current and plating time 0.5A 10 minutes or 2A 5 minutes As a result of the Hull cell test, the test pieces plated at 0.5A showed The area where the current density is about 0.3A/dm2 ^or higher has a semi-glossy uniform appearance,
A black film was formed in the area where the current density was less than about 0.3 A/dm ² , and this black film covered about 25% of the plated surface of the test piece. Moreover, the test piece plated with 2A had a uniform semi-glossy appearance on the entire surface, and could be used satisfactorily in cases where strong gloss was not required. In addition, using the above plating bath, plating was performed on a steel plate to a thickness of 5 μm at an average current density of 4 A/dm ² , and JIS
- As a result of a salt spray test based on Z-2371, the time required for red rust to appear on the sample was 288
It was time. Example 2 A Hull cell test and a salt spray test were conducted in the same manner as in Example 1, except that the additives shown in Table 1 below were used in place of sodium oleate in the plating bath of Example. . The results are shown in Table 2 below. Regarding Sample I, the salt water spray test results are shown for a sample in which a 5 μm thick galvanized film was formed using a conventionally used cyanide zinc plating bath.

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[Table] As is clear from Table 2, in the plating bath of the present invention, the area of the black film formed in the low current density area is significantly reduced, and a good glossy plating film is formed over a wide range of current density areas. is formed. Furthermore, the anti-corrosion properties of the resulting plating film are extremely superior to those of conventional galvanized films and zinc-nickel plating films.

Claims (1)

[Claims] 1 (i) Zinc chloride (as Zn ²⁺ ) 12.5 to 90 g/
, (ii) Nickel chloride (as Ni ²⁺ ) 5-60 g/, (iii) Ammonium chloride (as NH ₄ ⁺ ) 5-120
g/, and (iv) Sodium oleate, sodium octylphenoxyethoxyethyl sulfonate, sodium monolaurylglyceryl sulfate, sodium dioctyl sulfosuccinate, funnel oil, 1,5
- Contains 0.2 to 20 g of at least one anionic surfactant selected from sodium diisopropyl-7-naphthalene sulfonate and sodium polyoxyethylene-β-naphthol sulfate, and Zn ²⁺ /Ni ²⁺ (weight ratio) = 0.2 to 2.5, and an electrolytic zinc-nickel alloy plating bath characterized in that the pH is adjusted to 4.7 to 7.0 with ammonia water.