Abstract
Rates of Dissolution and Formation of Oxide FilmsFor the purpose of studying hard anodizing process, the rates of dissolution and formation of oxide films on aluminum were examined in the baths consisting of mixed solutions of sulfuric, oxalic, and citric acids.The results obtained were as follows.(1) The rate of dissolution of films in electrolytes decreased with the fall of temperature. The dissolution of films remarkably decreased by the addition of oxalic acid to sulfuric acid.(2) The rate of formation of films in sulfuric-oxalic acid baths was maximum when the concentration of sulfuric acid was high and that of oxalic acid was low. However, the concentration of the former was necessarily maintained at lower than 10-20g/l, or it would give an uneven film at more than 0.1% (by weight) against the latter.(3) The rate of formation increased by the addition of more than 30g/l of citric acid to sulfuricoxalic acid baths. In particular, the rate remarkably increased when the concentration of sulfuric acid was less than 10g/l and that of oxalic acid was also low.(4) The rate of formation was maximum at around room temperature, which were most effective for obtaining hard anodized films.(5) It was observed that the rate of dissolution during electrolysis increased twofold with each temperature rise of 25°C, which was very smaller than that in other baths. However, the value was 2-5 times as large as that during immersion.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
