CLASSIFICATION OF TYPES OF CORROSION AT DEFECTIVE PARTS OF COATED STEEL FROM CATHODIC POLARIZATION CURVE.

The measurements of the cathodic polarization curve by the potentiodynamic method were made along with the observation of rust width by the naked eye in order to classify types of corrosion at the defective parts of coated steel plate. The measurements show that, for a variety of coated steels, the cathodic curve of the defective parts exhibiing non-pitting corrosion had a characteristic peak, while one showing pitting corrosion was normal without any peak. Moreover, it was shown that this new estimation method for determining the type of corrosion could be applied to almost all coated steel panels.