COMPARISON OF THE CORROSION OF CARBON STEEL IN NATURAL SEAWATERS - EVIDENCE OF MIC?

SUMMARY: The corrosion behaviour of carbon steel was investigated in natural seawater sampled from two different locations to determine the potential of microbiologically influenced corrosion (MIC) in these waters. Laboratory-based immersion test have been undertaken with 1020 carbon steel in seawater from Port Melbourne and Queenscliff (Victoria). Evidence of accelerated low water corrosion (ALWC), which is related to MIC, has previously been reported for sheet piling in the Queenscliff area. A range of metallurgical, chemical and microbiological measurements have been performed on the test samples including weight loss, 3D optical surface profilometry, scanning electron microscopy, energy dispersive X-ray mapping and MALDI–TOF analysis. While the results of some individual tests, including differences observed between metal coupons tested in the two seawater samples and differences between replicate samples, could potentially be linked to MIC the overall conclusion is that the corrosion observed could not be reliably assigned to MIC.