Corrosion accelerated exposure experiment simulating under seawater environment for organic coated steel materials

Abstract

In order to investigate and evaluate the corrosion characteristics of steel members more effectively under seawater conditions, the authors have developed an accelerated exposure experimental system to simulate under seawater environments. The acceleration coefficients of this experimental system were based on a study of the depths of corrosion actually found in structural steel members exposed to seawater environments for over 19 years. The accelerated coefficient for the splash zone was around 6·0. In the experiment reported, the system was used to investigate the corrosion behaviours of steel coated with epoxy resin, polyurethane resin and tar-epoxy resin and then subjected to damage from cross scribe lines or circular types of coating defect. Corrosion propagation was found to occur under the coating around the boundaries of these coating defects and macrocell corrosion was observed around the boundary areas. Methods of predicting corrosion propagation distances under the organic coating and the depths of corrosion under the coating defects were proposed based on the experimental results.