Damage to paint coatings caused by electrolyte immersion as observed in situ by scanning electrochemical microscopy

Damage to paint coatings caused by immersion in aqueous electrolyte solution has been observed in situ by scanning electrochemical microscopy (SECM). SECM was used to image the surface topography of coated metal samples as a function of time in chloride and sulphate solutions. The degradation is observed as a swelling of the polyester coating as a function of time of immersion in chloride solution. The aggressive effect of chloride ions towards coating degradation was established after very short exposure times. No indications of coating failure could be observed by either conventional electrochemical techniques or visual observation. In contrast, blistering could not be observed in a chloride-free sulphate solution. Chloride enhances degradation of the coating at a very early stage. (C) 2004 Elsevier Ltd. All rights reserved.