抄録
The dissolved amount, I-E curve, and normal electrode potential were determined in various concentrations (1×10-3-1M) of alkaline solutions for aluminum (99.50%) and its alloy (5052).
The dissolved amount was measured by gravimetric method and conductometric titration with carboxylic acid in dimethyl formamide.
The results obtained were as follows:
(1) The dissolved amount of Al-Mg alloy (5052) was much greater than that of pure aluminum (99.50%). It would be due to a local battery formed between aluminum and other metals.
(2) The normal electrode potential was increased in direct proportion to dipping time and finally reached a constant value.
(3) I-E curve had a distinct inflection point in 0.025-0.05 M-NaOH solution and it was considered to be the decomposition voltage of aluminum ionic species in the solution.
(4) Conductivity and electrolysis time by a.c. were inversely proportional to alkaline concentration. It was believed that the fact was due to the peeling of sodium aluminate and re-dissolution of aluminum.
The precipitate separated from sodium hydroxide solution of high concentration was estimated to be γ-Al2O3·3H2O and γ-Al2O3·H2O by means of X-ray analysis and thermal decomposition method. The precipitation was prevented by the addition of sodium gluconate and sorbitol.
