JPS6296691A - Zn-ni alloy plating method - Google Patents

Abstract

PURPOSE:To obtain alloy plating having fine luster and superior corrosion preventiveness by carrying out electroplating with a Zn-Ni or Zn-Ni?-Cr plating bath contg. a specified org. complexing agent. CONSTITUTION:A plating bath is prepd. by adding 0.001-1mol/l cyclohexenedicarboxyimide and/or benzoic sulfimide as an org. complexing agent to an aqueous soln. contg. 0.1-4mol/l Zn ions, 0.1-4mol/l Ni ions and 0.2-10mol/l sulfate ions or further contg. 0.01-4mol/l tervalent Cr ions. Electroplating is carried out with the plating bath to obtain alloy plating having fine luster and superior corrosion preventiveness. Especially in case of Zn-Ni-Cr plating, the corrosion preventiveness is further improved.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for producing a Zn-Ni alloy plated steel sheet with excellent plating properties, and is useful not only as a Zn-plated alternative steel plate but also as an Sn-plated alternative steel plate. The present invention relates to a method for plating surface-treated steel sheets.

(Prior Art) Zn plating has conventionally been carried out by a melting method or an electrolytic method, and due to the sacrificial anticorrosion property of Zn, excellent substrate corrosion protection has been achieved by thick plating.

In recent years, the corrosion resistance of Zn plating has progressed, and Zn-fi JL alloy hot-dip plated steel sheets, Zn-Fe or Zn-Ni alloy electroplated steel sheets, composite plated steel sheets, etc. have been developed as steel sheets to replace Zn plating. It is provided as a steel sheet with special plating properties, and its excellent surface coverage, cathodic protection, and other properties protect the substrate from corrosion in a variety of corrosive environments.

Regarding these plating properties, for example, when referring to a Zn--Ni plated steel sheet, it exhibits a galvanic current suppressing effect several times more than that of Zn plating under the influence of chlorides. It has been pointed out that these materials have advantages not only in corrosion resistance but also in terms of weldability and processability as materials for automobiles and the like.

A known example of Zn-Ni plated steel sheet is JP-A-57
-207193 and JP-A-56-20190, which show that N1 content ranging from several inches to 20 inches has excellent corrosion resistance or resistance after coating. In addition, attempts have been made to improve the surface appearance and gloss of Zn-Ni plating in addition to corrosion resistance.
No. 52194 describes a method for controlling ion concentration, liquid movement speed, or current density, and furthermore,
114686. JP-A-58-34189 describes the addition of organic brighteners such as alkyl betaine type organic compounds, polyacrylate copolymers, and aryl olefin aldehydes. Furthermore, JP-A-55-54588 and JP-A-55-131193 describe the combined addition of hexavalent chromium ions and strontium ions to a Zn-Ni-based bath; It has been shown that the gloss is improved, while the addition of chromium significantly improves the corrosion resistance.

(Problems to be Solved by the Invention) Generally, plating is carried out using a plating apparatus such as a horizontal type, a vertical type, or a radial cell type at an optimum range of concentration, pH, current density, flow rate, temperature, etc. In particular, current density and flow rate have a large effect on plating characteristics. Zn-
In Ni-based alloy plating, it is generally difficult to obtain glossy plating at relatively low current densities, while at high current densities, properties such as density deteriorate. Therefore, the present invention uses Zn
It is an object of the present invention to provide a plating method in which an alloy exhibiting relatively stable and excellent properties is deposited by containing a specific organic complex in a -Ni-based plating bath.

Furthermore, Zn--Ni alloy plating deposits an alloy with good surface properties under optimal plating conditions. but.

The gloss of this surface is translucent. Therefore, the present invention aims to provide a method for plating a Zn--Ni based alloy plate with further decorative properties and excellent gloss by adding a specific complexing agent.

Furthermore, the present invention aims to provide a Zn-Ni plating method with excellent corrosion resistance and gloss both indoors and outdoors, and a Zn-Ni-Cr alloy plating method with particularly excellent corrosion resistance. The present invention aims to provide a plating method using a plating bath that is advantageous in terms of hygiene and Cr plating efficiency.

(Means and effects for solving the problem) In order to achieve the above-mentioned object, the present invention has been developed to coat the surface of a plated original plate with zinc ions, nickel ions and sulfate ions as main components, or to complex them with an aqueous solution containing chromium ions. Electroplating is carried out at a relatively high temperature using a plating bath containing either cyclohexene dicarboximide or benzoic sulfimide, or both, as an agent. However, the plating bath composition is 0.1 to 4 mol/l of zinc ions, 0.1 to 4 mol/l of nickel ions, and 0.2 to 10 mol/l of sulfate ions.
l is the basic bath, and if it contains chromium ions, it contains 0.001 to 4 mol/l of trivalent chromium ions,
To this, add cyclohexene dicarboximide or benzoic sulfimide alone or both at 0.001
The pH is usually 1 to 1 using a bath containing 1 mol/l of additive.
5.5, temperature is 40℃~65℃, current density is 1-150
Plating within the A/dm' range. Although the above-mentioned complexing agent used in the present invention has a limited solubility, it has excellent properties in a relatively high temperature range, including common sense, and is a preferable additive from the viewpoint of temperature controllability.

Furthermore, by adding all of the organic complexing agent according to the present invention, an alloy exhibiting a characteristic luster can be relatively stably deposited at both low and high current densities. Plating varies depending on plating conditions such as current density and flow rate, but Zn
In -Ni system and its Zn-Ni-Cr plating, an alloy exhibiting a glossy appearance resembling tinplate is precipitated, especially when the flow rate is set to about 20 m/min or more. Zn-Ni-C
In R plating, the surface properties are mainly affected by the Cr content, but by adding the complexing agent of the present invention and adjusting the current density, flow rate, etc., an alloy with a high Cr content can be precipitated. The corrosion resistance after plating can be greatly improved.

Although the above-described plating method relates to Zn-old yarn, and particularly to Zr1-Ni-Cr plating, the organic complex of the present invention is also effective in plating old-Cr yarns.

In the present invention, predetermined characteristics can be obtained with one layer of plating, but if one layer is insufficient, several layers of plating can be applied to improve the characteristics. After plating according to the present invention, the anticorrosive properties can be further improved by performing appropriate surface conditioning using a known method and performing electrochrome plating or chromate treatment.

Further, the surface of already known metal plating such as Zn, Ni, Fe, fiJl, etc. or alloy plating thereof may be pretreated as necessary, and then alloy plating may be applied by the method of the present invention.

In the present invention, the plating amount is 0.01~l OOf/lr?
, usually one side 5~409/rr? plated on. The N1 content in the alloy plating film is in the range of 1 to 35%,
Furthermore, when using a bath containing Cr, C in the plating film is
The r content ranges from 0.1 to 20%. Further, in the present invention, the plating/bath concentration is carried out within the above range so that gloss and corrosion resistance can be obtained at the same time, and plating with excellent properties cannot be obtained outside the above range. The plating bath of the present invention may contain iron ions and cobalt ions as alloy components.

Alloy components may be added as carbonates, hydroxides, or oxides. Furthermore, an alkali metal, alkaline earth metal, aluminum or ammonia sulfate, chloride, fluoride, and boric acid may be added to the plating bath of the present invention.

These are effective in improving bath conductivity and stable plating deposition.

The chromium ions in the bath are mainly trivalent chromium ions, but may also exist as divalent ions or ions of other valences. The plating bath of the present invention contains hypophosphorous acid, hydrazine, glycine, N-chloroacetic acid/alkylimidacillin, dioctylsulfosuccinic acid, etc.
By adding more than one species in combination, plating properties and plating stability can be further improved. The amount of these compounds added is a maximum of 6 mol/l. Furthermore, in the present invention, if the pH of the plating bath is less than 1.0 or more than 5.5, no plating will occur or no glossy or corrosion-resistant alloy will be deposited.

Electroplating properties are affected by pretreatment. Plating pretreatment is usually carried out by cathodic treatment in an alkaline aqueous solution containing 1 to 30% sodium hydroxide, sodium silicate, etc.
If necessary, anodization in an aqueous alkaline solution or immersion in an aqueous acid solution is added to perform the entire treatment. These treatments may be performed alternately, and the electrolytic treatment is performed at a temperature of room temperature to 95°C, respectively, at 1 O for 1 to 30 seconds, preferably for a treatment time of 10 seconds or less.
~200 tydrr? It is carried out at a current density of .

Zn and Ni are used as the anode during plating in the present invention.

Soluble anode such as Zn-Ni, Ni-Cr or T
1. Insoluble anodes such as carbon are preferred.

(Example) Example 1 A plating original plate was subjected to cathodic electrolysis for 10 seconds at 80° C. and 10 A/dffI'' using carbon gold as a counter electrode in a 10% NaOH aqueous solution, followed by anodic electrolysis for 5 seconds under the same conditions. ,
It was degreased, then immersed in a 5% H2So4 aqueous solution for 5 seconds to pickle, and then plated under fire conditions.

PH1,9 Temperature 45℃ Current density 25A/drrt' time
30 seconds flow rate 5om/min Result benzoic sulfimide? An alloy with a shiny appearance similar to tinplate was deposited by using a plating bath containing On the other hand, when a plating bath containing no benzoic sulfimide was used as a comparison ψ, only an alloy with a grayish, translucent appearance was deposited.

Example 2 A plating original plate pretreated in the same manner as in Example 1 was plated under the following conditions.

PH 1,8 Temperature: 55° C. Current density: 25 A/ai Time: 30 seconds Flow rate: 40 m/min As a result, a transparent glossy alloy was deposited by using a plating bath containing cyclohexenecarboximide. On the other hand, as a comparative example, when a plating bath containing no cyclohexene dicarboximide was used, only an alloy with a grayish, translucent appearance was deposited.

Example 3 A plating original plate pretreated in the same manner as in Example 1 was plated under the following conditions.

PH2.0 Temperature: 45° C. Current density: 25 A/drrt Time: 30 seconds Flow rate: 40 m/min As a result, by using a plating bath containing benzoic sulfimide, an alloy with a glossy appearance resembling tinplate was deposited. On the other hand, as a comparative example, when a plating bath without benzoic sulfimide Kanakura was used, only an alloy with a grayish, translucent appearance was deposited.

Further, in this example, the plating bath contained Cr2 (304
) Even with a plating bath that does not contain 3, a shiny alloy is precipitated and has excellent corrosion resistance. Comparing the corrosion resistance with this example using a plating bath containing chromium ions, this example has a 3% Hack.The results of a scratch test in an aqueous solution at 35°C for 1 week show that the amount of iron rust generated is 4 minutes. The corrosion resistance was even better.

(Effects of the Invention) As described above, alloy plating with excellent gloss and corrosion resistance can be obtained by containing a specific organic complex in the Zn-Ni plating bath, and in particular, Zn-Ni-Cr plating. In some cases, the corrosion resistance is even better, and its use as a surface-treated steel sheet can be expanded in a wide range of fields.

Claims (1)

[Claims] Zinc ions 0.1 to 4 mol/l and nickel ions 0.1 to 4 mol/l.
1 to 4 mol/l, sulfate ion 0.2 to 10 mol/l, or trivalent chromium ion 0.01 to 1.
Glossiness characterized by electroplating using a plating bath containing 0.001 to 1 mol/l of cyclohexene dicarboximide or benzoic sulfimide, each singly or both, in an aqueous solution containing 4 mol/l. Zn-Ni alloy plating method with excellent corrosion resistance