Phosphating
Conversion coating process where metal surfaces react with phosphate solutions to form an adherent crystalline top layer for corrosion protection and paint adhesion.
Phosphating is a surface treatment that creates a crystalline protective layer on the metal. The layer serves as corrosion protection and improves adhesion for subsequent painting. When welding, you must remove the layer in the weld area beforehand, otherwise you get pores and poor weld quality. The layer burns off during welding and can introduce impurities into the weld pool. For the treatment itself: the part must be grease-free and clean, otherwise the layer will not adhere properly. Stick to the specified times and temperatures of the respective bath, then the layer will be uniform.