Analysis of a premature failure of welded AlSl316L stainless steel pipes originated by microbial induced corrosion

Abstract

This paper analyses the causes of the premature failure of welded AISI316L stainless steel (ss) pipes which formed part of a sea water cooling circuit. The service time of the pipes was 8 months. The laboratory tests carried out consisted of metallography tests, δ-ferrite determination, intergranular corrosion susceptibility, cyclic anodic polarization curves, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray photo-electron spectroscopy (XPS). The study presents typical forms of microbial induced corrosion (MIC) in AISI 308L and 316L ss in contact with natural sea water. The research is completed with the performance of bacteriological tests which demonstrate that the bacteria which cause the localized corrosion are of the sulphate-reducing genus >desulfovibrio> and the sulphide-oxidizing genus >thiocapsa>.