The evaluation of anticorrosive automotive epoxy coatings by means of electrochemical impedance spectroscopy

摘要

Different epoxy primer coatings for metal substrates were investigated by electrochemical impedance spectroscopy (EIS). The variables were the substrate (cold rolled steel, phosphatised cold rolled steel and phosphatised electrozincated cold rolled steel), the epoxy primer (containing a Pb anticorrosive pigment and non-toxic paint containing Al and Fe oxides) and curing temperature (low temperature 160degreesC and high temperature 180degreesC). The primers showed excellent behaviour when applied on phosphatised steel and very poor electrochemical characteristics on phosphatised electrozincated steel. The non-toxic primer performed better than the Ph coating on phosphatised steel and electrozincated steel while it performed in a similar way to Ph primer on steel. The curing temperature had a big effect on the primer behaviour. The Ph coating performed better when it was cured at a low temperature. The coat adhesion to the substrate was tested by cathodic disbonding. It was found that the primers have very good adhesion to phosphatised steel and poor adhesion to phosphatised electrozincated steel. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 19]