Strengthening Natural Protection

The purpose of passivation is to reinforce the steel’s natural protective oxide layer. Additionally, surface-level iron and certain superficial inclusions dissolve, contributing to enhancing the steel’s corrosion resistance.

What is Passivation?

• Passivation is a treatment with a mild acid (oxidizing agent) to strengthen the protective oxide layer.
• During mechanical polishing or grinding on stainless steel, the surface becomes active and loses its passive properties.
• To regain rust protection, the passive surface needs to be recreated.
• If this happens spontaneously with the presence of foreign particles on the surface, they will remain in the passive layer, potentially providing less corrosion protection than creating the oxide layer through a controlled process.

Chemical Post-treatment – Different from Pickling

Passivation acts as a chemical post-treatment for mechanically processed items without annealing. Especially, finely sanded, and blasted surfaces benefit from subsequent passivation. A passivation bath closely resembles pickling, but has a higher acid content, and functions differently.

Passivation – A Gentler Process

Because passivation does not contain an activator, it is a milder process than pickling. This is why it does not remove annealing or other chromium oxides through passivation.

Does Not Affect Surface Smoothness

A significant advantage of passivation is that surface smoothness is not affected, making it excellent for treating ground or blasted surfaces.

Post-treatment for Electropolishing

Passivation can also be used as a post-treatment for electropolishing to increase the thickness of the passive layer and quickly make the surface more hydrophobic.

Learn more about how Calamo works with passivation and the various standards available here.