Application of Scanning Kelvin Probe to Measure Delamination on Thick Organic Coatings Used for Offshore Marine Applications

摘要

The scanning Kelvin probe (SKP) is a non-destructive technique for measuring the surface distribution of the Volta potential with a high spatial resolution of a few tens of micrometers. The SKP technique allows in-situ studies of the localized corrosion processes under atmospheric weathering conditions, on both metal surfaces and underneath organic coatings. For metals covered by organic coatings, the corrosion often starts at defects such as scribes, pineholes and cut-edges and propagates through delamination at the metal/polymer interface.In this paper, it is shown that the technique may be successfully used as a non-destructive technique to follow the delamination of painted steel and underfilm corrosion in-situ under atmospheric weathering conditions for thick organic coatings applied on steel for naval and offshore marine applications. SKP has been applied to study the delamination from a scribe for paints with various thicknesses on steel. From the results, it is shown that the mechanisms of delamination are largely depending upon the weathering conditions. The results are explained through the formation of opposite gradients in potential between the scribe and the intact polymer/steel interface.