CORROSION BEHAVIOR OF THE AL-ZN SPRAYED OPEN RACK VAPORIZER IN SEA WATER

摘要

Al-Zn spray coating is employed as protection for the heat transfer tubes of the Open Rack Vaporizer (ORV) . The corrosion behavior of Al-Zn coatings was investigated. Blisters were observed after two weeks on the Al-2wt%Zn coating by an erosion corrosion test in sea water after two weeks. However, no blisters appeared on the Al-15wt%Zn coating even after three weeks testing. It is suggested that the blistering behavior could be due to localized corrosion at voids in the coating by the current distribution measurement. This corrosion is emphasized in Al-2wt%Zn coating which has more ability to form passivation than Al-6wt%Zn or Al-15wt%Zn. These alloys also have an advantage in stability of corrosion potential and effective range as a sacrificial anode compared with Al-2wt%Zn. The contents of 6wt% and 15wt% of Zn in alloys gave long term adhesion and effect as a sacrificial anode, hence they could work as a better protective coatings than Al-2wt%Zn.