Synergistic effects of Cl- and Cu2+ ions on corrosion of pure Al and Al alloys in aqueous solutions at 363K

Pipes of 3003/4043 clad aluminum alloys are used in air conditioning systems and are exposed to flowing relatively high-temperature solutions (353 - 373K). In the present investigation, the corrosion behavior of pure aluminum and 1050-, 3003-, and 4043-aluminum alloys was examined by immersing in 1.57 x 10(-3) kmolm(-3)-CuSO4 and 0.57 kmolm(-3)-KCl solutions at 363K for 1week. Mass losses of the specimens during the immersion were measured after removing corrosion products, and the specimen surfaces were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). Mass losses of all specimens examined were 0.1 - 0.7 % in the Cl- solution and 2-3 % in the Cu2+ solution. The mass losses in a solution including both Cl- and Cu2+ ions at the same concentrations were 4 - 8 %, showing a synergistic effect of Cl- and Cu2+ ions. This effect was more with higher concentrations of Si in the Al alloys. The SEM and EDS analysis showed that Cu particles are deposited on Al phases and Fe-enriched areas of the specimen surfaces in the Cu2+ solution, while deposited on Si-enriched areas as well as on Al phases and Fe-enriched areas in the Cl-/Cu2+ solution. Copyright (c) 2013 John Wiley & Sons, Ltd.