アルミニウムの硬質陽極酸化におよぼす電源波形の影響について

Abstract

Studies were made of the effects of application of three kinds of direct currents (single phase full-wave, three phase half-wave, and six phase half-wave) and other five kinds of currents (interrupted, pulse, PR, periodic alternate [DC or AC], and superimposed [DC and AC] currents) on hard anodic oxidation coatings of aluminum. Specimens were anodized at 0°C for 45min, in 100g/l of H2SO4 containing 15g/l of C2H2O4.The results of the experiments were as follows:(1) The color of coating anodized by applying a direct current was dark, but it became light when a negative current was applied.(2) The adhesion of coating was extremely poor when PR current or periodic alternate (DC or AC) current was applied.(3) The bath voltage was higher than those by other currents when single phase full-wave or three phase half-wave direct current was applied, and the cell size of these coatings was larger. Except for superimposed (DC and AC) current, it was observed by scanning electron microscopy that the cell size became somewhat larger when a current including AC was applied.(4) The thickness of coating was larger and its hardness was higher than those by other currents when a direct current was applied.(5) The coating ratio was high when a direct current was applied, but it became lower when a negative current was applied.(6) The coating ratio was higher when the density was higher; in other words, the density of each coating indicated almost the same tendency as the value of coating ratio.(7) The results of the measurement of sulfur intensity of coating by X-ray microanalyzer revealed that the quantity of sulfur contained in the coating was less than that by a direct current when superimposed (DC and AC) current was applied, although a large quantity of hydrogen sulfide gas was evolved near the specimens.