Chromate conversion coating
A chromate conversion coating forms on zinc or aluminum surfaces via chemical conversion. It protects against corrosion and improves adhesion for organic coatings.
Physico-Chemical Mechanism of Action
The chromate conversion coating forms through a chemical reaction between the metal (zinc or aluminum) and an environment containing oxygen and water. This leads to a stable oxide with increased strength and corrosion resistance.
Metallurgical Significance & Risks in Welding
The coating protects the metal from environmental contamination and corrosion. It also improves adhesion for subsequent coatings, such as paints or lacquers. If these coatings are missing or damaged, it can lead to wear issues and reduced service life.
Workshop Practice & Action Guidelines
Before applying a coating, the chromate conversion coating must be carefully cleaned. This can be done using chemical cleaners or mechanical polishing. The temperature and time of the coating processes must be precisely controlled to ensure even layer formation.