RELATION BETWEEN THE FLUCTUATIONS OF CORROSION POTENTIAL AND THE CORROSION RATE OF ALUMINUM.

Relation between the fluctuations of corrosion potential and the corrosion rate has been investigated for aluminum immersed in NaCl solutions for 24 to 240 hours at 30 degree C. The fluctuations of corrosion potential were recorded with a strip chart recorder for one minute, and were expressed as the number of waves (n). The corrosion rate was expressed in two forms, the rate of pit growth (v) determined by the calibrated microscope technique and the mean corrosion rate (r) determined by the weight loss. It was found that the value of n changed with the variation of v, when the aluminum was immersed in 5 multiplied by 10** minus **1 M NaCl solution, in 5 multiplied by 10** minus **2 M NaCl solution containing 20 mg/l Cu**2** plus , or in 5 multiplied by 10** minus **2 M NaCl solution containing 20 mg/l Cu**2** plus and 10** minus **1 M NaNO//3. The value of n also changed with the variation of r for the aluminum immersed in 5 multiplied by 10** minus **2 M NaCl solution containing 20 mg/l Cu**2** plus . The mean value of n was approximately proportional to v and r in NaCl solutions with and without addition of Cu**2** plus .