Bacterial settlement on welded stainless steel samples exposed to seawater occurred more rapidly in the heat-affected zone (HAZ) and the root of the weld as compared to the parent metal. Preferential
attachment of bacteria to a network of surface cracks was an occasional feature, which became more conspicuous during mild anodic polarization of the samples. In a less corrosive fi-esh water system,
bacterial settlement was more random, until application of anodic polarization which triggered bacterial settlement patterns analogous to the sea water system. Supplementary experiments on bacterial response to pre-initiated corrosion sites in the form of pits and scratches reinforced the idea that bacteria preferentially colonize areas of anodic electrochemical activity and/or metal ion release. Key words: sea water, fresh water, stainless steel, weldment, localized corrosion, bacterial settlement, electrochemistry, polarization, anodic activity, heat-affected zone, heat-tint cracks