Pickling – Quality, what else?
Pickling is used to remove all impurities from stainless steel surfaces with the objective of preserving a pure metal surface. The protective passive layer can only be formed on such pure metal surfaces.
Scale and heat tints are not passive layers and are thus potential points of origin for corrosion. The same goes for ferritic residue, which is practically inevitable during production, particularly on construction sites. The pickling process removes all impurities using chemicals and results in metallically pure surfaces.
Passivation means forming the protective passive layer. It doesn‘t matter whether this is done in the natural way with humidity and oxygen (within days) or with passivation chemicals (oxidation agents, within minutes). However, as there is a risk of corrosion until the complete formation of the passive layer, it is recommended that passivation is done in the chemical way. Passivation can only be done on pure metal surfaces. This means that passivation is always the second step, after a pickling process.