Probing Coating Degradation on AA2024‐T3 Using Local Electrochemical and Chemical Techniques

Abstract

The local electrochemical and chemical characteristics of intrinsic breakdown sites on organically coated aerospace alloys were investigated. Local electrochemical impedance spectroscopy and mapping were used in conjunction with capillary electrophoresis, local pH, and local open‐circuit potential measurements to classify the electrochemical activity and chemical properties of individual failure sites on organic coated AA 2024‐T3 exposed to an aqueous environment. Panels coated with vinyl or polyurethane and exposed to chloride solutions were examined. Several different types of blister sites, both active and passive, were observed and characterized. A strong correlation was observed between the underfilm chemical characteristics, the electrochemical impedance, and the visual appearance of the blisters. Evidence suggestive of hydrolysis of the polyurethane coating was found during the propagation of coating defects. © 1999 The Electrochemical Society. All rights reserved.