Study On Corrosion Of 5052 Aluminium Alloy In Seawater

Aluminium alloys have low density, good thermal conductivity and excellent corrosion resistance.They are widely used for seawater desalination technology by people. Varied types of aluminium alloy have different corrosion resistance in seawater. Even the corrosion resistance of aluminium alloys with the same trademark can be different due to the influence of various factors in production process. In order to reduce costs and enhance the stability of euipments, it is important to study the corrosion resistance of different aluminium alloys.Domestic and imported 5052 aluminium alloys were used in this paper. Primarily, the influence of variation of properties of simulated seawater on the corrosion resistance of aluminium alloys was investigated using potentiodynamic polarization and alternatingcurrent impedance techniques.The results indicated that the variation of pH, salinity, temperature, dissolved oxygen concentration and heavy metal ions concentration of seawater could influence the Ecorr, Icorr, Rm and Rt of both 5052 aluminium alloys. This showed that the corrosion resistance of both 5052 aluminium alloys varied in certain degree. When the pH value decreased,the Icorr increased and the sum of Rmand Rt reduced. It indicated that the corrosion resistance of both alloys degenerated. The Icorr increased and the sum of Rm and Rt declined with the rise of salinity, showing the reduction of corrosion resistance of both materials. As the temperature went up, the Icorr increased and the sum of Rm and Rt diminished. This illustrated the degradation of corrosion resistance of both alloys. As the concentration of dissolved oxygen or heavy metal ions increased, the Icorr increased and the sum of Rm and Rt decreased. The corrosion resistance of both 5052 alloys reduced. Compared with the domestic 5052 aluminium alloy, the imported 5052 alloy exhibited better corrosion resistance in the above-mentioned experiment.The surface topographies of both 5052 aluminium alloys after immersion in the simulated seawater with different values for 15 days were also investigated in this paper.The results indicated that a large number of corrosion protuberances appeared on surfaces of both 5052 aluminium alloys. The corrosion resistance of both 5052 aluminium alloys were influenced by the variation of pH, salinity, temperature, dissolved oxygen concentration and heavy metal ions concentration of seawater. As the pH dropped, corrosion protuberances became more obvious and corrosion products multiplied. As the salinity increased, corrosion protuberances became more obvious and corrosion products multiplied. When the temperature is 50℃, the corrosion protuberances of both alloys were not very obvious. As the temperature arised, corrosion products multiplied. The corrosion products of both alloys were not obvious when the dissolved oxygen concentration was very low. A large quantity of corrosion protuberances occured on surfaces of 5052 aluminium alloys after adding heavy metal ions into seawater and we can see the obvious accumulation of corrosion products.According to the results, we can weaken the corrosiveness of seawater by adopting a lot of measures such as deoxidation and removing heavy metal ions. In this way , the corrosion resistance of alloys can increase.