An Electrochemical Study of the Corrosion of Painted Iron

Abstract

The corrosion protective value of approximately 50 different paints was determined by means of an electrochemical method which has been previously described. This determination involved the measurement of the change in the potential of the painted iron with time when wet with water for 24 hr. or less. It was found that the interpretation of the time‐potential curves, which were automatically plotted by a recording vacuum tube electrometer, was facilitated if the test was conducted in a nitrogen atmosphere. The results obtained with the electrochemical or potentiometric method compared favorably with those obtained in a one‐year outdoor exposure test. Such differences as were found were shown to be due to either deterioration or improvement in the paint film as the result of weathering.