The Blue-White Passivation Fluid for Passivation and Shielding of Galvanized Workpiece by Trivalent Chromate Conversion Coating

The reaction of SiO32-and NaF was carried out under certain conditions to generate a solution containing SiF62-capable of promoting film-formation and H4SiO4 capable of shielding passivation coating. After introducing chromium sulfate, nickel sulfate, cobalt nitrate, sodium nitrate, lanthanide salts, aniline type corrosion inhibitor, and surfactants into the above-mentioned solution, a blue-white trivalent chromate passsivation fluid for the passivation and shielding of galvanized workpieces was formulated. The appearance, corrosion resistance, and heat resistance of the passivation coatings prepared from the solutions containing different doses of SiO32- were investigated. Results indicated that the trivalent chromium passivation coating prepared from the solution containing 7. 20 g/L SiO32- was evenly blue and bright and had excellent corrosion resistance and heat resistance.