The theory of metallic corrosion in the light of quantitative measurements.— Part II

Abstract

In a previous paper it was shown that if dilute solutions of potassium chloride were allowed to act upon metallic zinc in the presence of oxygen, the corrosion-time curves obtained by means of the observed absorption of oxygen gas were exponential for part of their course. The reason why this particular form of curve was obtained was considered to be the gradual falling off in the concentration of chlorine ions in the experimental conditions of limited volume of solution. For N/10000 and N/5000 solutions the agreement between the experimental and calculated curves was satisfactory up to about 25 days except for a short initial period of two or three days. After about 25 days the experimental curves fell notably below the calculated values, and the suggestion that the reason for this discrepancy was mainly the barring out of chlorine ions from the anodic areas by means of accumulations of corrosion products received some support from the fact that chlorine ions were actually found in solution even after long periods of experiment with the N/5000 solution, in which this discrepancy was most pronounced, but since none were found in the more dilute solutions it seemed probable that some other factor was also operative.