THE ROLE OF ION-EXCHANGE INTERACTIONS IN THE PASSIVATION AND LOCALIZED CORROSION OF METALS

A model is examined which views the depassivation of metals as a proce ss in which anions L(-n) migrate through the oxide-hydroxide films on the metal(ion exchange mechanism of adsorption and migration through a n anion exchange membrane to the Me/MeO(n) boundary). Electrochemical and corrosion studies were carried out on Al, Mg, and carbon steel whi ch had preliminary formed surface adsorbed siloxane ion exchangers wit h variously charged functional groups in Cl- containing electrolytes. It was shown that the presence of negatively charged groups lead to in hibition, while positively charged groups lead to activation of the de passivation mechanism. The role of charge and the ion exchange propert ies of the metal surface during depassivation are examined.