The peculiar feature of cathodic protection in seawater has the capability to form mineral calcareous deposits such as magnesium and calcium on metal surfaces. It is assumed that OH − ions are generated close to the metal surface as a result of cathodic protection and generated OH − ions increases the pH of the metal/seawater interface outlined as the following formulae. (1) O 2 + 2H 2 O + 4e → 4OH − , or (2) 2H 2 O + 2e →H 2 + 2OH − . And high pH causes precipitation of Mg(OH) 2 and CaCO 3 in

more »

... H) 2 and CaCO 3 in accordance with the following formulae. (1) Mg 2+ + 2OH − →Mg(OH) 2 , (2) Ca 2+ + CO 3 2− →CaCO 3 . The focus of this study was to increase the amount of CO 3 2− with the injection of CO 2 gas to the solution for accelerating process of the following formulae. (1) H 2 O + CO 2 →H 2 CO 3 , (2) HCO 3− → H + + CO 3 2− . Electrodeposit films were formed by an electro-deposition technique on steel substrates in solutions of both natural seawater and natural seawater dissolved CO 2 gas with different current densities, over different time periods. The contents of films were investigated by scanning electron microscopy(SEM) and X-ray diffraction(XRD). The adhesion and corrosion resistance of the coating films were evaluated by anodic polarization. From an experimental result, only CaCO 3 were found in solution where injected CO 2 gas regardless of current density. In case of injecting the CO 2 gas, weight gain of electrodeposits films hugely increased and it had appropriate physical properties.