Conversion Coating Formation
Conversion layer formation is a process in which a metallic surface is converted into a poorly soluble protective layer through chemical or electrochemical reactions. This layer protects against corrosion and improves adhesion of paints or coatings.
Physicochemical mechanism of action
Conversion layer formation occurs through the reaction of the metallic surface with an aqueous solution. For example, in chromating, the metal reacts with chromic acid, forming a thin chromated protective layer.
Metallurgical relevance & risks during welding
The conversion layer can prevent corrosion and increase the service life of components. However, it must be removed before welding, as it can impair melting and cause uneven stresses.
Workshop practice & instructions
Before welding, conversion layers must be thoroughly removed. This can be done using chemical cleaning agents or mechanical polishing methods. It is important to follow the manufacturer's specific instructions to ensure no corrosion or stress formation occurs.