MIC studies of buried potable water pipelines using semi-solid agar as an analogue for soil

Abstract

Seventy percent of the Australian water pipeline network, predominately critical transmissions mains, is constructed of ferrous materials which are highly susceptible to corrosion, particularly microbiologically influenced corrosion (MIC), when buried in soil. A novel technique for the study of MIC in soil to further the understanding of localized corrosion on the external surface of water pipelines is being developed. This novel test method utilizes agar to simulate both the physical structure and chemical components of soil more closely than the traditionally used aqueous solutions. This paper discusses initial electrochemical tests conducted on carbon steel exposed to semi-solid agar containing low concentration sodium chloride and a peptide based nutrient broth with and without Pseudomonas fluorescens present. Open circuit potential measurements for 3 and 24 hours durations were conducted followed by potentiodynamic scans. The sample surfaces were characterized with scanning electron microscopy. These initial results suggest that under these conditions, P. fluorescens increases the corrosion of the steel and that the more developed the nutrient film, with or without a biofilm present, the greater the kinetic drive for corrosion. This work is part of a continuing investigation into the mechanisms of microbial corrosion at the soilsteel interface of buried potable water pipes.