Trivalent chromium treatments
Hexavalent chromium-free conversion treatments

The first trivalent chromium-based passivates were developed commercially in the 1970s. The aim was to obtain a bluish-colored passivation film, mainly for decorative purposes. The relatively high cost of trivalent chromium salts meant that very small quantities of trivalent chromium were used in the passivation electrolyte (< 1 g · L ^–1), and the anti-corrosion performance of these coatings was consequently very limited (around 24 hours in the salt spray test before white rusting according to ASTM B 117-03).

These electrolytes are based on a combination of trivalent chromium salts and an oxidizing agent that replaces the chromate present in chromating with Cr^VI[9], mainly hydrogen peroxide....