Electroplating surface treatment methods

Posted by Kuajing Plus on January 7th, 2022

Electroplating is a method in which metal is precipitated from the electrolyte by the action of an applied current and deposited on the surface of the object to obtain a metal covering layer.

Galvanized:

Zinc is easily corroded in acids, alkalis, and sulfides. The zinc layer is generally passivated. After passivation in chromate solution, the passivation film formed is not easy to interact with moist air, and the anti-corrosion ability is greatly enhanced. In dry air, zinc is relatively stable and not easy to change color. In a water and humid atmosphere, it reacts with oxygen or carbon dioxide to form an oxide or alkaline carbonic acid film, which can prevent zinc from continuing to oxidize and play a protective role.

Applicable materials: steel, iron parts

chrome:

Chromium is very stable in a humid atmosphere, alkali, nitric acid, sulfide, carbonate solutions, and organic acids, and is easily soluble in hydrochloric acid and hot concentrated sulfuric acid. The disadvantage is that it is hard, brittle, and easy to fall off. Direct chromium plating on the surface of steel parts as an anti-corrosion layer is not ideal. Generally, multi-layer electroplating (ie copper plating → nickel → chromium) can achieve the purpose of rust prevention and decoration. At present, it is widely used to improve the wear resistance of parts, repair size, light reflection, and decoration.

Applicable materials: ferrous metal, copper, and copper alloy zero decorative chrome plating, wear-resistant chrome plating

Copper plating:

Copper is not stable in the air, and at the same time, it has a high positive potential and cannot protect other metals from corrosion. However, copper has high electrical conductivity, the copper plating layer is tight and fine, it is firmly combined with the basic metal, and it has good polishing performance. It is generally used to improve the conductivity of other materials, as the bottom layer of another electroplating, as a protective layer to prevent carburization, and to reduce friction or decoration on the bearing.

Applicable materials: black metal, copper, and copper alloy nickel-plated, the chrome-plated bottom layer

Nickel plating:

Nickel has good chemical stability in the atmosphere and lye and is not easy to change color, but it is easily soluble in dilute nitric acid. It is easy to passivate in concentrated nitric acid, and its disadvantage is porosity. To overcome this disadvantage, multi-layer metal plating can be used, and nickel is the intermediate layer. The nickel plating layer has high hardness, is easy to polish, has high light reflectivity and can increase the appearance and resistance, and has good corrosion resistance.

Applicable materials: can be deposited on the surface of various materials, such as steel-nickel-based alloys, zinc-based alloys, aluminum alloys, glass, ceramics, plastics, semiconductors, and other materials

Tin plating:

Tin has high chemical stability. It is not easy to dissolve in dilute solutions of sulfuric acid, nitric acid, and hydrochloric acid. Sulfides have no effect on the tin. Tin is also stable in organic acids, and its compounds are non-toxic. It is widely used in food industry containers and parts of aviation, navigation, and radio equipment. It can be used to prevent copper wires from being affected by sulfur in rubber and as a protective layer for non-nitriding surfaces.

Applicable materials: iron, copper, aluminum, and their respective alloys

Copper tin alloy:

Copper-tin alloy electroplating is to plate copper-tin alloy on the parts without nickel plating, but directly chromium plating. Nickel is a relatively rare and precious metal. At present, copper-tin alloy electroplating is widely used in the electroplating industry to replace nickel plating, which has good anti-corrosion ability.

Applicable materials: steel parts, copper, and copper alloy parts