Degradation mechanism of an acrylic water-based paint applied to steels

The behaviour, in conditions of total immersion, of an acrylic water-based paint applied to a St 35.8 steel, has been studied using electrochemical techniques. The data obtained have enabled a three-step mechanism to be proposed. In the first step, there is an increase in the activity of the system, as a consequence of the entry of water. In the second step, once a critical level in the water content has been passed, the inhibitor pigments are activated, and this leads to a decrease in the electrochemical activity. Finally, once that the pigments have been exhausted, there is a loss of the protective properties of the paint, with the result that the activity detected is similar to that of the bare metal. (C) 2003 Published by Elsevier B.V.