Abstract
The electrochemical polarization characteristics of coated all aluminum cans in a 1% NaCl solution were studied to establish a method for the determination of the area of coating defects. When specimens were cathodically polarized at a potential of -2.0V vs SCE, which is below the hydrogen evolution potential, the current immediately attained a stationary value. Additionally and importantly, a linear relationship was observed between the current and the area of coating defects, implying that the area of coating defects can be determined quantitatively from the catholic current at the potential of -2.0V. The present method is considerably more reliable than the conventional enamel rater value method where the specimens are anodically polarized in a 1% NaCl solution which causes the development of pits at the defect sites and, hence, overestimation of the defect areas.
Application of the present method for the evaluation of coating performance has also been discussed with specific examples.
