抄録
In this paper, the anodizing of aluminum was investigated using water-soluble aromatic amine (benzylamine) to compare with aliphatic amine. Investigations were conducted to determine optimum bath compositions for the anodizing of aluminum in organic alkaline baths (benzylamine-fluoride base) involving ammonium fluoride and organic acid salts (HCOONH4, CH3COONH4, (NH4)2C2O4, (NH4)2C4H4O6, (NH4)3C6H5O7). In the case of anodizing in baths containing organic acid salts, uniform films were formed, but non-uniform films were formed in baths without these additives. The thickest film (about 8μm) was formed in a 0.05mol/L benzylamine bath containing 0.1mol/L ammonium fluoride and 0.3mol/L ammonium acetate or in a 0.2mol/L benzylamine bath containing 0.1lmol/L ammonium fluoride and 0.2mol/L ammonium tartrate by anodizing for 30min at 20°C with a current density of 1A/dm2. The film formed in the 0.2mol/L benzylamine bath containing 0.1mol/L ammonium fluoride and 0.1mol/L ammonium tartrate was the hardest (Marten's scratch hardness test, load 50gf, about 13) and the film formed in 0.1mol/L benzylamine bath containing 0.1mol/L ammonium fluoride and 0.1mol/L ammonium citrate showed the highest corrosion resistance. SEM observation found that pores of films prepared in back containing ammonium acetate were about 30∼50nm in diameter, while these prepared in baths containing other organic acid salts were about 50nm.
