Scanning Kelvin Probe assessment of steel corrosion protection by marine paints containing Zn-rich primer

Zinc rich primers provide corrosion protection of steel constructions under heavy corrosive conditions such as offshore environments. In general, the paint contains different polymeric layers including the zinc-rich primer with a total thickness larger than 00 mu m that significantly delays the degradation of the paint and the observation of corrosion failures. For prediction of corrosion failure and a quick ranking of paint systems, a new sensitive and non-invasive method for assessment has to be developed. Two commercial coatings with different corrosion protection ability were selected for the study. Scanning Kelvin Probe (SKP) was used to determine the sacrificial protection of steel by multilayer paint systems containing zinc rich primer during exposure to accelerated corrosion tests under atmospheric or under immersed conditions. Scanning Electron Microscopy - Energy Dispersive X-Ray Spectrometer (SEM-EDX) techniques were applied to analyse the cross sections after exposure. It is shown that SKP could quickly access the level of cathodic protection of the steel substrate underneath of industrial thick marine paints.