Passivation Frequently Asked Questions

Passivation is a chemical treatment that boosts the corrosion resistance of stainless steel by eliminating free iron and contaminants, forming a protective chromium oxide layer on the surface.

Most stainless steels, particularly austenitic varieties, can undergo passivation. The degree of enhancement depends on the alloy type and the surface chemistry quality.

Passivation clears away iron and minor traces of light rouge from the surface, improving corrosion resistance. For heavier rouge, derouging is necessary before applying passivation.

Derouging targets visible iron oxides and metal oxides, using stronger acids to achieve a clean surface appearance. Passivation, on the other hand, focuses on removing trace amounts of free iron from the top 3 to 4 molecular layers of an already clean surface to enhance corrosion resistance.

Passivation typically lasts 8 to 12 hours, depending on the system size. Smaller systems may require 8 to 10 hours, while larger ones often need 12 hours. Derouging can take 4 to 24 hours based on the surface condition.

We are equipped to use either citric or nitric acid, but citric acid is our primary method of passivation. Citric acid is a safer, eco-friendly option that’s simpler to dispose of and more user-friendly.

We assess passivation by sampling before and after treatment to measure the chromium-to-iron ratio, evaluating the passive film's quality. At Pure Edge Passivation, we use the Koslow Passi-Flash 3036 test kit for accurate, recordable results that meet industry standards.

No, passivation only impacts the surface at a molecular level. It improves the passive layer's chemistry by increasing stable chromium atoms relative to reactive iron atoms in the top 3 to 5 atomic layers, leaving the visible finish unchanged.

Yes, the passive layer, which spans 2 to 5 molecular layers, can be stripped away by welding, polishing, exposure to reducing environments, or corrosion, which can reverse passivation and lead to an active or corroded surface.

Yes, pre-cleaning is strongly advised before passivation. It clears away contaminants from the stainless steel surface, ensuring the passivation solution can fully interact for the best results.