Corrosion protection of carbon steel by coating with epoxy polyester powder containing zinc and polyaniline

Abstract

Normally the epoxy resins are used to coat the carbon steel for corrosion protection. In this research, the epoxy polyester powder was work, with the addition of zinc and polyaniline (PANI) for carbon steel coating. PANI was synthesized by chemical oxidative polymerization method using ammonium peroxydisulfate as oxidant. The resulting polymer was characterized by FT-IR spectroscopy and had conductivity in the range of 3 to 4 x 10-2 S/cm, measured by a four-point probe meter. PANI 5 phr was added. Two types of zinc particles, zinc dust and zinc flake were employed. The content of zinc dust and zinc flake was varied. These were 17 formulations of epoxy polyester powder. After depositing on carbon steel by electrostatic spray coating, they were subjected to the anti-corrosion test using the salt spray technique according to ASTM B-117 and then evaluating with ASTM D-1654. When the amount of zinc increased, size and frequency of blistering appeared to be smaller. It was also observed that the formulation with zinc flake 50 phr showed better anti-corrosion than the others. The results indicated that the presence of zinc was necessary as the zinc corroded and blocked further corrosion attack and zinc flake particles enable to secure the electrical conductive connection in the coating and create an impermeable barrier through their particles. Electrochemical impedance spectroscopy measurements in 3.5 wt. % NaCl were performed to study corrosion properties with the exposure time. The physical and mechanical properties of all the coated steel, such as adhesion to substrate, impact resistance and gloss had also been evaluated.