Studies on the Effect of Structure and Thickness of Coatings and Contaminants on the Corrosion of Steel Surfaces

Abstract

The presence of soluble salts (chloride, sulphate & nitrate) and their effect at the coating-metal interface was studied along with the chemistry of coating, water and oxygen permeability, coating thickness and metal surface preparation. Of course, the macroscopic defects, caused due to improper designing, handling, etc. can also not be over looked. What so ever the coating be the surface anomalies have their own role in deciding the coating life. Nevertheless there are still some coating systems which can reduce or postpone corrosion mechanism. Five different popular, coating systems (e.g. phenolic, polyurethane, cardanol, vinyl & alkyd) were exposed to humidity for different time, 100 and 400 hours, and the under film corrosion was determined. The study reveals that carefully designed coating systems applied on the substrate with some fundamental knowledge can significantly improve the performance of coating and metal protection as well.