JPS61117298A - Treatment of surface - Google Patents

Abstract

PURPOSE:To form a bronze film of high quality on the surface of a metallic material by electroplating by adding a specified nonionic surfactant and formaldehyde to a plating bath. CONSTITUTION:To a bronze electropalting bath contg. copper sulfate. stannous sulfate and sulfuric acid as principal components are added 0.2-30g/l one or more kinds of nonionic surfactants such as polyoxyethylene-polyoxypropylene condensation products represented by formula I, polyoxyethylene- polyoxypropylenediimine compounds represented by formula II and polyoxyethylene-polyoxypropylenediimine compounds represented by formula III and 4-20ml/l formaldehyde. When electro-plating is carried out in the resulting plating bath, a bronze film contg. no pinholes and having a uniform semimat appearance can be formed.

Description

[Detailed Description of the Invention] [Object of the Invention] The present invention provides a method for surface treatment of metal materials in which electrolytic bronze plating is applied using a sulfuric acid acidic bath using additives described below. The present invention relates to a method for surface treatment of metal materials, characterized in that

[Prior art]

Conventionally, the method of electroplating a copper-tin alloy, that is, bronze, on a metal material is as follows.

Methods using 1) cyanide steel-tin layer salt bath, 2) copper cyanide-tin pyrosinate bath, 5) pyrosinate bath, 4) sulfate bath, etc. are known. These baths are selectively used depending on the quality of the desired film, workability, etc. Low-pollution baths, especially sulfuric acid baths, require only smoothing, and the resulting bronze electrodeposit has properties such as semi-gloss and easy polishing.

Can be recommended.

Conventional sulfuric acid acid bronze plating conditions are as follows.

Sulfuric acid steel auso4e sa, o 50~50
f/ stannous sulfate Elu Day 04 50-50
t/ to sulfuric acid H, SO25G ~100 f
/l Phenol 5-1 op/l Gelatin 1.5-St/L Thiourea
α005P/l cathode and anode current density 15~I A/di temperature
18-25[deg.]C [Problem where the invention is about to disappear] However, in such a bath, it is not possible to individually quantitatively control each organic substance that is added in combination. Therefore, the Hull cell test was used to determine the electrodeposition ability of the bath, but it required a lot of experience and effort to obtain a bronze film of stable quality.

[Structure of the invention]

Taking these circumstances into consideration, the present inventor conducted extensive research on plating conditions with high productivity and workability that would allow a stable high-quality film to be obtained, and found that the following nonionic surfactant was used as an additive. It has been found that using a tin plating bath mixed with formalin, or in addition formalin as an additive, results in a high quality coating, i.e. a bronze coating with a uniform semi-gloss appearance and few pinholes. be.

The nonionic surfactant is (1) Formula %formula%) [In the formula, a+c must be a positive integer from 2 to 350.

b is a positive integer of 11 to 66] Polyoxyethylene-polyoxypropylene condensate represented by formula (2) [wherein m is a positive integer of 1 to 320, n is 8 to 60]
is a positive integer of 8 to 60, and q is a positive integer of 1 to 520.
is a positive integer] is a polyoxyethylene-polyoxypropylene diimine compound represented by the following.

The concentration of nonionic surfactant in this tin plating bath is set at 121% in order to sufficiently increase the leveling effect and obtain a good appearance.
71 or more is required, and if it exceeds 30 f/l, the effect will be saturated and it is uneconomical to add more than that.

These nonionic surfactants have a sufficient pressure leveling function even when added alone to a sulfuric acid acidic bronze plating bath, but the divalent tin ions in the bath are easily oxidized and the liquid is formed by tetravalent tin salts. It becomes cloudy easily.

Formalin contributes to leveling together with a nonionic surfactant, suppresses the oxidation of tin, and reduces the adverse effects of insoluble tetravalent tin salts on plating quality, such as increase in pinholes and reduction in gloss.

If the amount added is less than 4 rd/l, there is no difference in plating quality compared to the case without the addition, and if it exceeds 20 rd/l, the effect is saturated, and adding more than that is uneconomical.

There are no particular restrictions on the type of metal material to be plated, and any material can be used. Moreover, the shape of the material, ie, the type of strip, processed product, etc., does not matter.

This metal material to be plated was subjected to normal pretreatment such as alkaline degreasing, electrolytic degreasing, and activation treatment to adjust the surface to be suitable for electroplating, and then the nonionic surfactant of the present invention or formalin was added. Tin plating is applied using a sulfuric acid acid plating bath, followed by washing and drying.

The back steel plating material thus obtained had a uniform semi-glossy surface and a good film with few pinholes. Furthermore, the only additives are a nonionic surfactant and formalin, and quantitative analysis is possible using a known method.

Next, Examples and Comparative Examples will be described.

[Examples and comparative examples]

After the thin bronze strip was alkaline degreased, electrolytically degreased, washed with acid, and neutralized, it was plated with 1 μm bronze in the following sulfuric acid acid bath.

The copper bath before sulfuric acid and plating conditions are as follows.

0u80. -5H4os
o t7't8nS0. 50 f/L
a, so, 1 ao
Tit bath Temperature: 25°C Current density: 3A/d/Next, from a bath containing a nonionic surfactant represented by formulas 11 to (3) and a mixture of formalin added to this treated material, and a bath containing conventional additives, Table 1 shows the results of testing the bronze plating film obtained.

Additive (1) formula %formula%) [In the formula, a+c must be a positive integer of 26.

b is a positive integer of 30] Polyoxine ethylene-polyoxy7-propylene condensate additive (2) represented by the formula [where m is a positive integer of 60, n is a positive integer of 71] ] Polyoxyethylene-polyoxypropylene diimine compound additive (3) represented by the formula [wherein p is a positive integer of 71 and q is a positive integer of 60] Polyoxyethylene represented by the formula -Polyoxypropylene/Diimine Compound Table 1 Porosity represents the number of pinholes in 1-Also.

As mentioned above, the present invention is capable of obtaining a surface-treated material with good appearance and excellent surface properties with low porosity with good workability by adding a nonionic surfactant and further formalin to the bronze plating bath. Became.

Claims (3)

[Claims] (1) In a surface treatment method for metal materials in which electrolytic bronze plating is applied using a sulfuric acid acidic bath, one or more of the nonionic surfactants shown in formulas (a) to (c) below are added to the sulfuric acid acidic bath. A surface treatment method characterized by performing bronze plating using a bath. (A) Formula HO (C_2H_4O)_a-(C_3H_6O)_b
-(C_2H_4O)_c-H [in the formula, a+c is 2 to 35
a positive integer of 0, and b is a positive integer of 11 to 66.] A polyoxyethylene-polyoxypropylene condensate represented by: (b) Formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [In the formula, m is a positive integer from 1 to 320, and n is from 8 to 60.
is a positive integer] A polyoxyethylene-polyoxypropylene diimine compound represented by: (C) Formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [In the formula, p is a positive integer of 8 to 60, and q is a positive integer of 1 to 320] Polyoxyethylene-polyoxy Propylene diimine compound. (2) The surface treatment method according to claim (1), using the nonionic surfactant in an amount of 0.2 g/l to 30 g/l. (3) The surface treatment method according to claim (1), wherein bronze plating is performed using a sulfuric acid acid bath to which 4 ml to 20 ml/l of formalin is further added.