Compared with other metals, zinc is a relatively cheap and easily plated metal. It is a low-value anti-corrosion coating and is widely used to protect steel parts, especially against atmospheric corrosion, and for decoration. Plating techniques include tank plating (or rack plating), barrel plating (for small parts), blue plating, automatic plating and continuous plating (for wire, strip).
Classification
According to the classification of electroplating solutions in China, it can be divided into four categories:
1. Cyanide Zinc
Because (CN) is highly toxic, environmental protection has put forward strict restrictions on the use of cyanide in electro-galvanizing, and constantly promotes the development of cyanide-reducing and replacing cyanide electro-galvanizing bath systems, requiring the use of low-cyanide (micro-cyanide) electroplating baths .
After electroplating by this process, the product quality is good, especially the color plating, and the color remains well after passivation.
2. Zinc galvanized
This process is evolved from cyanide zinc plating. There are two major factions in China, namely: a) "DPE" series of Wuhan Material Insurance Institute; b) "DE" series of Radio and Television Institute. Both belong to zincate zinc plating with alkaline additives, and the pH value is 12.5~13.
Using this process, the lattice structure of the coating is columnar, and the corrosion resistance is good, which is suitable for color galvanizing.
Note: After the product is out of the tank—>; water washing—>; light output (nitric acid + hydrochloric acid)—>; water washing—>; passivation—>; water washing—>; water washing—>; blanching—>; drying—>; aging Treatment (80~90℃ in the oven.
3. Chloride Zinc
This process is widely used in the electroplating industry, accounting for up to 40%.
After passivation (blue white), chrome can be replaced by zinc (comparable to chrome plating), especially after adding water-soluble varnish, it is difficult for a layman to distinguish whether it is galvanized or chrome plated.
This process is suitable for white passivation (blue white, silver white).
4. Sulfate Zinc
This process is suitable for continuous plating (wire, strip, simple, thick and large parts and components), and the cost is low.
Features
The purpose of electrogalvanizing is to prevent steel objects from being corroded, improve the corrosion resistance and service life of steel, and at the same time increase the decorative appearance of the product. Steel will be weathered, water or soil corrosion over time. The steel that is corroded every year in China accounts for almost one-tenth of the total amount of steel. Therefore, in order to protect the service life of steel or its parts, electro-galvanizing is generally used to process steel.
Since zinc is not easy to change in dry air, and can produce a basic zinc carbonate film in a humid environment, this film can protect the internal parts from corrosion damage, even if the zinc layer is damaged by some factor. In some cases, zinc and steel combine over time to form a microbattery, with the steel matrix protected as a cathode. Summary Electrogalvanizing has the following characteristics:
1. Good corrosion resistance, meticulous and uniform combination, not easy to be entered by corrosive gas or liquid.
2. Because the zinc layer is relatively pure, it is not easy to be corroded in acid or alkali environment. Effectively protect the steel body for a long time.
3. After passivation by chromic acid, it can be used in various colors, which can be selected according to customers' preferences. The galvanizing is elegant and decorative.
4. The zinc coating has good ductility and will not fall off easily during various bending, handling and impact.
