Abstract
The influence of chloride and chlorate ions on the anodizing of aluminum in sodium hydroxide solutions was studied.
The baths used were composed of sodium hydroxide (0.1M) and chloride and chlorate (NaCl, NaClO, NaClO3, NaClO4) ions and bath volume was 1L. Anodizing was carried out for 30min at a current density of 3A/dm2 and a bath temperature of 10°C.
The concentration of additives at which no pitting occurred was 0.005M. The thickest film (5.5μm) was formed in an NaOH-NaClO bath.
It is suggested that Cl- is changed to ClO- by electrolysis in NaOH solution and promotes anodizing as an oxygen supplier.
