1990 年 41 巻 4 号 p. 417-422
The effets of the addition of organic acid salts and polyhydric alcohols were investigated in alkaline baths of aliphatic amines (monoethylamine, diethylamine and triethylamine), containing ammonium carbonate and ammonium fluoride.
Under constant-current anodizing in the baths without additives, bath voltage increased rapidly, and burning was observed on the corners of the specimens, while in baths with organic acid salts (ammonium oxalate, ammonium tartrate and ammonium citrate) added, bath voltage decreased and uniform films were formed.
The thickest (about 17μm) and most uniform film was obtained in an amine (0.1mol/L) bath containing ammonium carbonate (0.4mol/L), ammonium fluoride (0.2mol/L), ammonium citrate (0.1mol/L) and propylene glycol (0.1mol/L).
It was found by SEM observation that the pore diameter in anodized films formed in monoethylamine-carbonate-fluoride baths are about 600Å, larger than those in films formed in diethylamine-carbonate-fluoride baths or triethylamine-carbonate-fluoride baths.