Chloride Ion Interactions with Oxide-Covered Aluminum Leading to Pitting Corrosion: A Review

Abstract

Metals and alloys such as aluminum (Al), stainless steels, andnickel-based alloys exhibit corrosion resistance in a wide range ofenvironments due to the presence of protective, passive oxides. However,in environments that contain aggressive anions such as chloride, Cl-,the passive film becomes unstable and degrades locally causing filmbreakdown and pitting corrosion. A number of theories describing theinitiation of pitting corrosion have been postulated and discussed butto date there is no consensus on the mechanism of breakdown. Since allcurrent mechanisms require Cl- interactions for oxide film breakdown inCl- containing environments, the question is what is the nature of theinteraction of aggressive anions such as Cl- with the passive film,adsorption and/or absorption, leading to pitting? This communicationfocuses on the interaction of Cl- with the passive oxide film on purealuminum by reviewing and summarizing the available experimental dataconcerning Cl- interactions. It should also be noted that theobservations for Cl- interactions with Al reviewed and summarized hereinmight not be applicable to all metals and alloys. (C) The Author(s)2014. Published by ECS. All rights reserved.