A-SEM STUDY ON THE GALVANIC PROTECTION OF ZINC-RICH PAINTS

The research is focused directly to the cahodic protection mechanism of zinc-rich paints (ZRP). It is based on a systematic scanning electron microscope (SEM) observation of cross-sections of several ZRP coatings exposed for different time intervals to a 3% (by weight) sodium chloride solution. The effect of vehicle (binder) used in the paint formula and the effect of zinc particle content are considered. As the anodic behaviour of zinc particles depends very closely on coating microstructure, SEM observation of the latter is very useful to investigate the galvanic performance of ZRP. This study confirms that high zinc particle contents and the use of ethyl silicate as a vehicle favour the degree and duration of the cathodic protection. Depending upon whether the zinc particles act anodically or not their attack mechanism is radically different. Accordingly, two attack mechanisms of the zinc particles are proposed. © 1990 Chapman and Hall Ltd.