Estudio de la formación de picaduras en el aluminio y su modelación a escala de laboratorio mediante EIS

Abstract

The aluminum and their alloys slightly corrode when they are exposed to the atmosphere, that is why this metal is very often used in the industry and buildings. This behavior is due to the fact, as it is very well known, a passive film of Al203 is formed on the surface; however, activators anions such as cr cause of pitting corrosion. Traditionally, the fundamental cause of pitting corro­sion has been attributed to the local breakdown of the passive film formed on the surface, causing the dissolution of the metallic substrate. It is possible to deter­mine the resistance to pitting corrosion by the electrochemical stability of the protective film as well as their capacity to repassivate. The propensity to pitting of a given metal-electrolyte system is characterized by the pitting potential (Ep ), although it is only valid for pure aluminum. One of the electrochemical tech­niques most widely used now is the electrochemical impedance spectroscopy (EIS) that allows determining the corrosion rate of the metal by means of the utilization of an equivalen! circuir obtained and the Nyquist diagrams. Aluminum 3003 impedance diagrams in severa! conditions were obtained in NaCl 0.5 mol/L solution in order to study the pitting formation kinetic and compare it with the mechanism of the pitting corrosion that is produced during two years in an aluminum alloy exposed at the coastal zone.