Electrochemical Evaluation of the Corrosion Properties of Rare Earth Based Chemical Conversion Coatings on Aerospace Aluminum Alloy

Aluminum alloys are widely used in different industries and mostly in the aerospace one because of their light weight combined with excellent corrosion resistance in different aggressive media. The tendency to corrosion in the presence of halide ions however limits their applications, especially in specific atmospheric conditions and marine environments and as a result after thinning the oxide layer the halides attack the exposed metal [1]. Chlorides are known to be “aggressive”, inducing passivity breakdown resulting in different kinds of localized corrosion, such as pitting and cracking. It is suggested that chloride enhances the flux of metal cation vacancies through the passive film resulting in vacancy condensation at the metal/film interface and ensuing passivity breakdown [2]