Effects of Electric Current and Voltage on Aluminum Integral Coloring

Abstract

The effects of electric current and voltage on aluminum integral coloring in oxalic acid and malonic acid solutions were examined. The results obtained were as follows. (1) When a constant current was applied, integral coloring occurred at high voltages, but not at low voltages. The “coloring voltage” was over 80V. (2) In case of aluminum anodizing by using a high constant voltage in dilute solution, the specimen was colored in a short time (60sec.) and no change of the color was observed for a long (10min.) of electrolysis. (3) The current density increased with the rise of bath temperature even though at low voltages; however, the integral coloring of aluminum did not occur, except in the case of the following (4). (4) Aluminum was colored when a peak of current was present on I-t curves at a constant voltage. (5) The surface roughness of aluminum base increased with the increase of applied voltage: that is, the surface roughness was higher at higher applied voltage.