Some new insights into organic coating breakdown have been obtained by examining coated steel samples after various periods of exposure to 3% NaCl solution, using a novel combination of two powerful techniques. Scanning acoustic microscopy (SAM) was used to detect disbonding and blistering, possible even beneath optically opaque organic coatings. The scanning Kelvin probe (SKP) was used to map electrochemical potentials, identifying anodic and cathodic re ions at a defect and beneath the surrounding coating. SKP showed that although initially anodes, were established at the defect surrounded by cathode areas, subsequent deposition of corrosion products can sometimes lead to relocation of the anode to beneath the coating. SAM images, acquired concurrently, revealed the development of blisters at the new anode sites. (C) 2004 Elsevier Ltd. All rights reserved.