STUDY OF THE EFFECT OF ANODIZATION PARAMETERS ON THE STRESS CORROSION CRACKING BEHAVIOR OF AZ61 MAGNESIUM ALLOY
Magnesium and its alloys have attractive physical properties for engineering applications. In structural usage, these materials are advantageous owing to their lower specific mass than that of steel and aluminum alloys. However, they are susceptible to corrosion and several studies are carried out in order to minimize this phenomenon, focusing, for example, on the development of surface treatments such as anodization. In addition, as well as high strength metallic materials such as high-strength and low-alloy steels (HSLA), magnesium alloys are subject to stress corrosion cracking. The aim of the present work is to study the effect of anodizing parameters of the AZ61 magnesium alloy on its stress corrosion cracking behavior. The effect of the anodizing parameters on the morphology, thickness, roughness and composition of the anodized layers will be investigated. The initial stage of the work, depicted here, consisted of undertaking anodizing treatments of the AZ61 magnesium alloy using different concentrations with constant current density. In later stages, different anodizing parameters such as electrolyte composition, anodizing current density and time were tested. The results showed that the concentration was not effective to improve the electrochemical behavior of the material. On the other hand, upon increasing the anodizing current density and time, a favorable effect was observed on the corrosion resistance. Anodizing electrolytes 3 M KOH + 0,15 M Na2SiO3 + 0,1 M Na2B4O7.10H2O) and 3 M KOH + 0,5 M Na3PO4) also formed the oxide films with the best characteristics against corrosion magnesium alloy AZ61, in relation to the as-received state. The results showed that solution 3 M KOH + 0,15 M Na2SiO3 + 0,1 M Na2B4O7.10H2O) and solution 3 M KOH + 0,5 M Na3PO4) improved the electrochemical properties against material degradation making their corrosion potentials less negative and their corrosion current densities have decreased.