Atmospheric corrosion behaviour of pure Al 1060 in tropical marine environment

In this study, atmospheric corrosion behaviour of pure Al 1060 after 1-48 months of exposure in a tropical marine environment was studied. The corrosion kinetics was evaluated by weight loss measurement and pit depth calculation. The rate controlling steps as well as the effect of the native oxide film and the corrosion product layer on the corrosion process were analysed via electrochemical impendence spectroscopy. The results showed that synergetic effect of the deposition rate of chloride ions and time of wetness resulted in an abnormal increase in weight loss and an obvious fluctuation in corrosion rate. During the initial exposure period, corrosion was controlled by charge transfer process attributed to the limited corrosion area. With the increasing exposure duration, the rate controlling step was changed to diffusion due to the barrier effect of the corrosion products. Simultaneously, initiation of the new corrosion areas and the growth of the stable pits dominated the corrosion process during this period, resulting in a lower charge transfer resistance, a larger pit depth and a bigger corrosion area.