Potential Distribution Measurement of Under-film Corrosion by Scanning Kelvin Probe

Abstract

In this paper the filiform corrosion of painted steel substrates was analyzed with a scanning Kelvin probe. The substrates were painted with clear acryl paint, and the dry film thickness was 5μm. In order to induce filiform corrosion, knife scribed specimens were set in a corrosive environment. (5%NaCl solution spray and 40°C 80%RH) By using the scanning Kelvin probe, a potential on the head of filiform corrosion was detected as less noble which showed anodic site. It is possible, with this technique, to measure the under-film corrosion.