Electrochemical Properties During Film Degradation of Coated Steel

 Organic coatings are widely used to steel structures of power transmission and distribution systems as one of effective methods for corrosion protection. The detection of the degradation of these coatings can be used for indicating their life, that is, necessity of maintenance coatings.  In order to investigate the evaluation methods for degradation of coatings for power transmission and distribution systems, atmospheric exposure tests for twenty seven months and some accelerated corrosion tests such as immersion tests used salts water were carried out. 

 Following these tests, the electrochemical behavior of the exposed specimen was measured by using alternating-current (AC) impedance and current-interrupter (DC) techniques. Furthermore typical degraded area of the coated film was analyzed using electron probe micro analyzer.

  In this report, electrochemical behaviors such as film impedance during degradation of coated steel were summarized and the relationship between the degradation of coated film and electrochemical behavior compared with the AC and the DC techniques was discussed based on the data obtained from corrosion tests mentioned above.