Zinc-tin alloy electroplating method

Abstract

The invention discloses a technological process of a zinc-tin alloy electroplating method and a preparation method of an electroplating liquid prepared by using the process. The technical process comprises two times of thermal degreasing, two times of washing, acid hydrolysis (cathode), washing, acid washing (30% hydrochloric acid), two times of washing, oil removing through alkaline electrolysis (anode), two times of washing, activating (5-10% hydrochloric acid), two times of washing, and electroplating; meanwhile, the quality of the electroplating liquid is improved; a plurality of electroplating additives such as a complexing agent, a brightening agent, polyglycerol, a polarization type brightening agent and a reducing agent are added in the electroplating liquid. The electroplating liquid disclosed by the invention is high in stability, can be produced for a long time but not changing plating, is quick to deposit and is strong in depositing adhesion power; when the tin content of the formed electroplating layer is about 70 percent and the tin content of the formed electroplating layer is about 30 percent, the formed plating layer achieves relatively good corrosion resistance, has the salt mist property achieving 144 hr white rust and 1000 hr red rust, and has good corrosion resistance against sulfur dioxide and good plating layer softness; the plating layer can be subjected to a bending test.

Description

technical field [0001] The invention belongs to the field of electroplating technology, and in particular relates to a zinc-tin alloy electroplating method. Background technique [0002] Electroplated zinc-tin alloys have been widely used as anti-corrosion protective layers for metals such as steel, copper, and nickel. Under normal atmospheric conditions, compared with pure zinc coating, the corrosion resistance of tin-zinc alloy coating is significantly improved than that of zinc coating. This is because tin-zinc alloy coating contains tin, which is corrosive to zinc and dissolves. It has an inhibitory effect and makes the alloy coating less prone to pitting corrosion. Although the addition of tin has the effect of inhibiting zinc from being corroded, at present, the tin mass fraction of zinc-tin electroplating coating is generally about 60%~85%, but the content of tin added is higher than 70% will cause the surface of the plated parts to appear white and foggy, without br...

AI Technical Summary

Problems solved by technology

Under normal atmospheric conditions, compared with pure zinc coating, the corrosion resistance of tin-zinc alloy coating is significantly improved than that of zinc coating. This is because tin-zinc alloy coating contains tin, which is corrosive to zinc and dissolves. It has an inhibitory effect and makes the alloy coating less prone to pitting corrosion. Although the addition of tin has the effect of inhibiting zinc from being corroded, at present, the tin mass fraction of zinc-tin electroplating coating is generally about 60%~85%, but the content of tin added is higher than 70% will cause the surface of the plated parts to appear white and foggy, without brightness, and less than a certain percentage will lead to a decrease in corrosion resistance. In addition, it can be known from the standard electrode potential of the metal that Sn 2+ The standard electrode potential of zinc is equal to -0.14V, and the standard electrode potential of zinc is equal to -0.763V. There is a big difference between the two. , due to the presence of Sn 2+ , Sn in the crossing solution 2+ easily oxidized to Sn 4+ Causes the plating solution to be diffuse and turbid, affects the quality of the plating solution, and increases the post-operation process

The problems existing in the above zinc-tin alloy electroplating process have seriously hindered the development of this method. Therefore, it is urgent to develop a method that can maintain the stability of the plating solution in the electroplating process, simplify the operation process, ensure that the coating crystallization is fine and has good resistance. Zinc-tin alloy electroplating method for corrosion resistance and brightness

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