Electrozinc passivation is the process of forming a uniform, dense, well-bonded zinc coating on the surface of a component using electrolytic principles.
Author: Anna
Electrozinc passivation is the process of forming a uniform, dense, well-bonded zinc coating on the surface of a component using electrolytic principles. The passivation process is designed to reduce the chemical activity of the zinc and is usually carried out using a chromate solution to passivate the zinc, resulting in the formation of a chromate conversion film layer on the surface of the zinc layer.
The process characteristics of electroplated zinc passivation include:
Colored passivation film: In the formulation for colored passivation, the passivation solution is acidic and the zinc layer undergoes a redox reaction with the chromic acid in the passivation solution to form trivalent chromium and hexavalent chromium compounds with the zinc, where the trivalent chromium compounds are bluish-green in color, and the hexavalent chromium compounds are ochre-red or brownish-yellow in color, which together constitute a colored passivation film.
Self-repairing function: the colored passivation film has self-repairing function, when the passivation film is damaged, in the air with high humidity, the hexavalent chromium compound dissolves in water to form chromic acid, which continues to react with the zinc layer to form a new passivation film.
Quality control: Passivation time, temperature, cleaning and baking aging and other parameters have an important impact on the passivation effect, need to be strictly controlled.
In practice, the single-sided passivation process is an emerging process, mainly used for the electro-galvanizing treatment of automotive fuel tank plates. Through the unique coating roller input, simulation of “fingerprint resistance” signal, pipe switching and other methods to achieve the single-sided coating process requirements, to solve the zinc electroplating speed production after the single-sided plating process parameter mismatch problem