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6782090 
Journal Article 
Chromium-free fluorozirconate-based chemical conversion coatings on aluminum and aluminum alloys 
Xiao, X; Xu, L; Deng, Cx; Wang, T; Yang, J 
2011 
30 
10 
37-40 
INSPEC:12957864 
A chromium-free chemical conversion process suitable for aluminum and aluminum alloys was studied. The effects of main components and process conditions on the quality of conversion film were discussed. The optimal process conditions were obtained as follows: potassium fluorozirconate 1.0-2.0 g/L, hydrofluoric acid 0.5-1.5 mL/L, accelerant 4-6 g/L, magnesium nitrate (as oxidant) 8-12 g/L, temperature 40-60degC, pH 3.5-4.0, and oxidation time 4-6 min. The conversion film obtained from the process is uniform and compact, presents an iridescent color with bright luster, and has a adhesion strength of 1 grade and a corrosion rate of 0.019 89 g/(m2.h) in 5wt% NaCl solution at 35degC, showing similar performance to chromate conversion film. The coating sprayed on the conversion film dose not fall off after neutral salt spray test for 240 h.