Abstract
Cathodic current on a metal tends to increase the $OH^-$ neighboring to the metal surface, especially during electro-deposition in seawater. The increased pH at metal/seawater interface results in precipitation of brucite crystal structure-$Mg(OH)_2$ as following formula; $Mg^{2+}+2OH^-{\rightarrow}Mg(OH)_2$, that is typical mechanism of the main calcareous deposits-compound in electro deposited coating films. In this study, the effects of anode and current density on deposition rate, composition structure and morphology of the deposited films were systematically investigated by scanning electron microscopy(SEM) and x-ray diffraction(XRD), respectively in order to overcome the problems such as deposition rate and a weak adhesion between deposit film and metal surface. The adhesion and corrosion resistance of the coating films were also evaluated by anodic polarization test. The electro-deposited film formed by using AZ31-Mg anode had the most appropriate physical properties. Weight gain of electro-deposit films increased with increasing cathodic current. Electro-deposit prepared at $5A/cm^2$ current density shows better adhesion than that formed at $8{\sim}10A/cm^2$.
