2008 Volume 57 Issue 4 Pages 194-200
The effect of anodic oxide film structure, barrier type and porous type on galvanic corrosion resistance of aluminum in 0.5 kmol/m3 H3BO3 / 0.05 kmol/m3 Na2B4O7 with NaCl was examined by electrochemical random signal (electrochemical noise) analysis technique. When pitting corrosion occurs, rest potential suddenly decreases and current increases rapidly, and rest potential and current change with fluctuation during galvanic corrosion. The galvanic current change correlates closely with corrosion potential change. As the thickness of both types of anodic oxide films and decreasing of chloride ion concentration, the incubation time of pitting corrosion became longer, and incubation time of pitting corrosion of specimen formed porous type anodic oxide film is longer than that of specimen formed barrier type anodic oxide film. The inverse of incubation time increase with chloride ion concentration to the power of n, [Cl–]n. The value of n is between 1.2 and 2.5 in both oxide films.
