Corrosion Behavior of Al 6063 in Qatar's Desert and Marine Environments

Abstract

Aluminum and its alloys have been widely used outdoors, especially in construction, electrical engineering and other applications, due to their high corrosion resistance, thermal and electrical conductivity and relatively low cost. The corrosion behavior of aluminum alloys indoor was significantly investigated compared to the outdoor studies. In addition, there is no investigation so far regarding atmospheric corrosion either in marine or desert areas in Qatar.The aim of this article is to investigate the atmospheric corrosion behavior for different exposure times (six and twelve months) of welded and non-welded Al 6063 alloy with and without crevices at seven different sites in Qatar State that represent desert, industrial, coastal and marine environments. Avergae pit densities, pit depths, pit mouth areas and aspect ratios, pitting factor and corrosion rates for the alloy at each location were measured. In addition, electrochemical characterization techniques were used in non aggressive for the collected coupons to examine the effect of exposure on the naturally formed oxide layer. Furthermore, scanning electron microscope (SEM) coupled with energy dispersive X-ray (EDX) was used to study the susceptibility of studied alloys to intergranular corrosion (IGC) and the effect of sulfur compounds and chloride ions concentration on the suceptibility for this type of corrosion. The results showed that the number, the size and the depth of pits depend on the aggressiveness of the site environment. In addition, Al 6063 alloy has the tendency for IGC at the different environments. Chloride ions were responsible for the pitting initiation while, sulfur compounds were responsible for IGC propagation. The rate of corrosion for Al 6063 alloy specimens from different sites follows the following order: North field (marine) > Ras Laffan (on shore) > Seaside Mesaieed (on shore) > Halul Island (on Shore) > Industrial Mesaieed > Dukhan (on shore) > Desert. Figure 1