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Under cyclic wet-dry conditions, the deterioration process of the organic coating on carbon steel surface has been studied using electrochemical impedance spectroscopy (EIS) assisted by self-organizing feature map (SOM) network. According to the EIS characteristics, changing rate of impedance and the classification results by SOM network, the entire deterioration process can be divided into three main stages shown as follows. Stage I is the medium penetration into coatings, which is a slow process. Stage II is the corrosion initiation under coatings, which is a relatively fast transition period. Stage III is the corrosion extension which causes coating delamination and makes the coatings lose its corrosion protection eventually. Besides, the results indicate that SOM network is a very simple and effective technique for analyzing the deterioration process of organic coating. (C) 2007 Elsevier B.V. All rights reserved.