Abstract
The anodizing of aluminum was investigated in propylenediamine-fluoride solutions containing organic acid salts. Using a 0.1mol/L propylenediamine solution containing 0.2mol/L ammonium fluoride, uniform films about 10μm thick were formed, while in the above bath with the addition of organic acid salts (CH3COONH4:0.05mol/L, (NH4)2C2O4:0.05mol/L, (NH4)2C4H4O6:0.2mol/L, (NH4)3C6H5O7:0.1mol/L), thick films (about 14∼17μm) were obtained. Marten's scratch hardness tests (load 50gf) showed that the hardest film (20.2) was obtained in the bath containing ammonium acetate. The films formed in the baths containing organic acid salts yielded nearly the same results (75∼80sec) in alkali dropping tests. SEM observation showed that the surface of films formed in baths containing ammonium acetate or ammonium oxalate consisted of a mixture of small (approx. 300Å) and large (approx. 1000Å) pores.
