Microbial corrosion of aluminium alloys in mine water

Abstract

Since aluminium alloys are being considered for more extensive use in the mining industry, their susceptibility to corrosion in these environments should be determined. Various aluminium alloy samples, from in situ test rigs on two South African mines, were examined. It was found that their surfaces were colonised by a variety of microorganisms including sulphate reducing bacteria and Pseudomonas spp, Pitting and intergranular corrosion Were the main forms of attack. Immersion and electrochemical tests were car. jed out in mine water under both static and flow conditions. Aluminium alloys 1070, 5182,6063 and 6261 were exposed to cultures of Desulfovibrio desulfuricans, Pseudomonas aeruginosa and a mixed strain of sulphate reducing bacteria. Conversion coated and anodized samples were tested under flow conditions only. The presence of sulphate reducing bacteria in mine water presented an aggressive environment for aluninium alloys leading to pitting at alloying inclusions and intergranular attack. The involvement of FeS in the corrosion process was established. The alloys exposed to Pseudomonas cultures also underwent pitting corrosion. Anodizing and conversion coating were effective as temporary rneasures against microbially induced corrosion provided no defect or damage was present. The alloys were not recommended for use in mine waters