Pietro Luigi Cavallotti

Anodic oxidation and powder coating for corrosion protection of AM6oB magnesium alloys

Abstract In the present paper a protection process against corrosion for AM60B magnesium alloys is described. The coating consisted of an anodic oxide layer, obtained by microarc oxidation (MAO), covered with a powder coating layer. The MAO pretreatment improved the adhesion of the organic layer, which was responsible for the corrosion protection effect. The morphological and crystallographic structure of the anodic oxide was characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Salt spray tests were carried out in order to assess the quality of the anodic oxide powder coating system.

Electrochemical Behavior of Nickel ACD-Electroless Deposition

Deposition of metals and other materials (oxide, polymer, salt) from aqueous solutions without an external current are described in the literature as electroless deposition. The mechanism to explain ACD-electroless deposition of nickel layers are reviewed and the fundamental characteristics of the process underlined, in comparison with the nickel electrodeposition. Results obtained with the secondary current pulse method during deposition with the ACD-electroless process are presented and show the main differences between the two processes: ACD-electroless process shows a reversible behaviour, whilst electroplating process is strongly irreversible. The results are interpreted according to the reactions prevailing at the reacting surface and strengthened by the electrochemical characterization performed in the ACD electrolyte and in sodium hypophosphite only solution.