Study On Electrochemical Performance Of Sacrificial Anode Under Seawater Wet-dry Cycling

Seawater wet-dry cycling is a common corrosion condition in the ocean industry, such as water ballast tank condition. Metal alloys are severity corroded in this critical condition. There are a few literatures reported about the electrochemical properties of metal alloys in this condition .Most of them are about the cathodes performance, few are about the anodes. Anodes are effect to the protect of cathodes, so it is important to study the electrochemical properties of sacrificial anodes in the seawater wet-dry cycling.Three type sacrificial anodes are studied in this paper, Zinc alloy(Zn-Al-Cd),common aluminium alloy(Al-Zn-In-Cd) and high activity aluminium alloy(Al-Zn-In-Mg-Ga-Mn).Electrochemical impedance spectroscopy(EIS),potentiodynamic polarization and potentiostatic polarization are introduced to study the electrochemical properties of sacrificial anodes in seawater immersion and under wet-dry cycling. The morphologies of the corrosion products and the surface dissolution of the anode are examined. Conclusions as follows:Under seawater wet-dry cycling, the electrochemical properties of sacrificial anodes are decreased compared with seawater full immersion. In salt spray test, the electrochemical properties are the worst of all. Under different seawater- atmosphere cycling, the anode performance is also different. Concerning Zinc alloy(Zn-Al-Cd), the best electrochemical properties of sacrificial anode in three seawater- atmosphere cycling are under 2.5day seawater -7.5day atmosphere cycling. Under 1day seawater-1day atmosphere cycling, the properties are little worse and under 1day seawater-3day atmosphere cycling, the properties are the worst in the three seawater-atmosphere. Concerning common aluminium alloy(Al-Zn-In-Cd), under...