Investigation into mechanism of protection of pigmented alkyd coatings using electrochemical and other methods

This paper reports some work conducted on several different alkyd coatings. Electrochemical techniques particularly the electrochemical noise method (ENM) have been used to monitor the performance of two and three coat systems in sodium chloride solutions. For one of the coatings systems comparison has been made between the results from room temperature continuous immersion exposure and accelerated tests both a cabinet test and a high temperature immersion test and good correlation has been obtained. Detached films have also been examined to obtain mechanism information and to clarify how these alkyd coatings work to prevent corrosion. Both the DC resistance characteristics, the noise resistance and the inhibitive properties of extracts have been examined. These tests appear to give information which is useful in deciding how effective the coating will be both when intact and when it needs to protect at a break or scribe. The work provides pointers for investigations of low VOC coatings from renewable resources such as water soluble alkyd–linseed oil coatings