Experimental evaluation of the corrosion protection ability of PVDCoatings

摘要

In the past, research on the corrosion protection capability of coatings, which are applied by means of physical vapour deposition (PVD), was performed utilizing a variety of different characterization and evaluation methods. The PVD coatings revealed typically a higher corrosion resistance compared to the substrate material and therefore, the degradation of the substrate coating compound is predominantly caused by coating defects. In particular, the numbers of pin-holes, which enable a direct penetration of the substrate material by corrosive media, have an impact on the corrosion behaviour of the compound. Therefore, the examination of the density of these defects is a common way to evaluate the corrosion resistance of the substrate coating compound. Generally, the analysis of such defect densities uses electrochemical methods like dynamic polarisation or impedance spectroscopy. However, such analysis can be affected by passive defects, such as clogged pin-holes by corrosion products, which can cause potentially misleading results of the evaluation.