Effect of Surface Condition on Attachment of Bacteria to Stainless Steel Welds(Materials, Metallurgy & Weldability)
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Microbiologically influenced corrosion (MIC) is ubiquitous. Welds are reported to be prone to MIC due to the altered material surface characteristics. This leads to the notion that bioadhesion is influenced by the substratum microstructure. Little is known quantitatively about the preferential adhesion of bacteria on areas of varying microstructures. One of the important characteristics of weld is its microstructure and an important determinant in the biofilm formation is bioadhesion. Thus, a study addressing both these factors would provide the probable reason why the welds suffer preferential MIC attack. Experiments were carried out to study the effect of microstructure on the adhesion of a gram-positive bacterium, Bacillus sp. isolated from the residual water of an MIC affected effluent treatment plant. Weld samples (weld metal, HAZ and base metal separately) of two different materials viz. 316L and 304L stainless steel were tested. Area of bacterial adhesion showed significant difference between base metal, HAZ and weld metal of both the materials tested. Weld metal and/or HAZ harbored more bacteria in both the materials tested, with base metal showing the least. Also, a significant difference in percentage area of adhesion was observed between as welded and polished coupons of the same material. Since base metal, HAZ and weld metal of both the materials showed difference in area of adhesion in spite of the uniform surface condition, the influence of microstructure gathers significance. This preferential adhesion contributes very much to corrosion and can be considered as one of the factors causing MIC attack on welds.
- Transactions of JWRI
Transactions of JWRI 29 (1), 45-51, 2000-07