Sulphate-reducing bacterial activity as a parameter to predict localized corrosion of stainless alloys

Based on an understanding of the mechanism of localized corrosion and microbial growth kinetics, sulphate-reducing bacterial (SRB) activity is believed to be the key parameter influencing SRB corrosion of stainless alloys. Accelerated corrosion tests were used to examine the relationship between SRB colonization and localized corrosion susceptibility of stainless alloy heat exchanger tubes in fresh water. Experimental conditions simulated those of the natural systems. Data were corrected to develop a model to predict microbially-influenced corrosion (MIC) for the CHECWORKS(TM) cooling water module. These tests found no correlation between bacterial numbers and pit initiation. However. there did appear to be a correlation between bacterial activity (causing a decrease in corrosion potential, as a function of sulphide production), and pit initiation. Since no practical method for measuring SRB activity at plant sites is available, it is argued that assimilable carbon, nitrogen and sulphate concentrations, as well as flow rate, may be practical input parameters for CHECWORKS(TM). Crown Copyright (C) 2000 Published by Elsevier Science Ltd. All rights reserved.