Corrosion Protection Properties of Cobalt Salt for Water-Based Epoxy Coatings on 2024-T3 Aluminum Alloy

Hexavalent chromium compounds (Cr(VI)) have been effectively applied for corrosion protection of aluminum alloy in various processes such as conversion coating, sealing or rinsing for anodization and in the primer laye r... [1-3]. Nevertheless, their cancerous risk and their toxicity for environment required to restrict or eliminate their future use. Significant efforts have been proceeded in last decade to find environmentally friendly alternative inhibitors [4]. Among them, the organic compounds, including the heterocyclic compounds, organic phosphates or carboxylates... and sometimes the synergistic combinations of organic inhibitors have exhibited the high corrosion inhibition effect for the aluminum alloy 2024-T3 surface [5-8]. This effectiveness is based on the formation of a protective barrier film on the surface to avoid the diffusion of oxygen and aggressive species at the metallic surface. The formed film is on the basis of the electrostatic and chemical adsorption of organic molecules on the metallic surface. However, suffer from the fact that this film is normal unstable caused by the highly reversible adsorption of organic inhibitor, limiting the longterm protection for the metal [9]. The inhibition behavior of inorganic substances such as metal cations toward to the corrosion of aluminum alloys has been variously studied. The lanthanides cations (La, Ce, Y, Pr, Nd, Pm...) have been interested from the 1990s. It was shown that the presence of lanthanum or cerium on the aluminum surface hinder the anodic and cathodic processes [10,11]. The cerium cations gave a highest inhibition effect in comparison with other elements, this is due to the formation of the insoluble cerium hydroxide or cerium oxide film resulted by the reaction with the OH group during the cathodic process. However, in the chloride medium, composing with the mixture of Ce(OH)3, Al(OH)3 and Ce(OH)xCl3-x is relative thin for corrosion †Corresponding author: anhtruc.trinh@itt.vast.vn (Anh Truc Trinh) †Corresponding author: ttthuy@itt.vast.vn (Thu Thuy Thai) Corrosion Protection Properties of Cobalt Salt for Water-Based Epoxy Coatings on 2024-T3 Aluminum Alloy