The Effect Of The Ion Trap Pretreatment Process On Corrosion Of Aluminum Alloy Tube

Low temperature multi-effect distillation (LT-MED) is one of the second-generation desalination methods because of its advantages such as low operating temperature, simple pretreatment, high thermal efficiency, low cost of fresh water, etc. LT-MED can make use of residual heat, which is low grade, from power plant and chemical plant. Aluminum alloy tube is widely used in LT-MED because of its low density, high conductivity for heat and low cost. It is important to study the corrosion behavior of aluminum alloy in seawater in order to reduce cost and improve competitiveness of LT-MED.An experimental equipment of pretreatment system for LT-MED was built, where seawater was pretreated by the ion trap consisted of AA5052material. Based on the experiment, the concentration of Fe3+was analyzed quantitatively as the experimental temperature and residence time of seawater in ion trap were changed. The corrosive morphology of the aluminum alloy tubes was comparatively investigated. Meanwhile AA5052hanging pieces in seawater, which was filtered by ion trap in different conditions, were tested by the potentiodynamic polarization curve method. The effect of ion trap pretreatment process on corrosion behavior of AA5052was studied by the measurement of corrosive potential, corrosion current density and corrosion rate.Experimental results indicated that the concentration of Fe3+in seawater fell significantly as the pretreatment temperature increased and the residence time of seawater in ion trap extended. According to the polarization curves of AA5052in seawater after pretreatment, the pitting potential remained unchanged and the variation tendencies of corrosive potential were not consistent. Whereas, the corrosion current density and corrosion rate decreased as the pretreatment temperature increased and the residence time of seawater in ion trap extended. As a result, the corrosion resistance of AA5052in seawater was greatly improved.In brief, the corrosion of AA5052in seawater could be decreased by ion trap pretreatment process.