51316-7843-Metal-Microbe Synergy in Pitting Corrosion of Stainless Steels

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Product Number: 51316-7843-SG

ISBN: 7843 2016 CP

Author: Kamachi Mudali

Publication Date: 2016

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Stainless Steel (SS) is the workhorse material for diverse industrial applications due to its outstanding general corrosion resistance weldability mechanical properties and fabrication costs. However their susceptibility to localized corrosion and failures due to through wall pitting even in low chloride environment is a serious concern which needs international attention. Some major attempts were made by well-known groups to solve the mystery of the localized corrosion process of stainless steel. They have come up with several mechanisms regarding critical role played by MnS inclusions ennoblement sensitization and favourable adhesion of microbes etc. However till this date no consensus has been evolved and even now the process of localized corrosion is described as random sporadic and stochastic and prediction of time and initiation sites remains extremely difficult.We made an attempt to look into this age-old problem by combining both metallurgical and microbiological approach to come up with a Metal-Micro Synergy (MMS) mechanism for the localized corrosion aspect of stainless steels. The austenitic 316L SS popularly used as condenser material in cooling system of nuclear reactors and as pipelines and linings in oil and gas industry was selected as the study material. Earlier studies in our laboratory had clearly indicated favourable adhesion of manganese oxidizing bacteria on SS surfaces and acceleration of pitting. The role of MnS inclusions was confirmed by adhesion studies at different applied potentials surface characterisation studies using SEM and EDAX and immersion pitting studies with ferric chloride solution. However biofilm community analysis with state of the art biofilm quantification tools deeper chemical investigation at biofilm interfaces elemental analysis of the passive films under the influence of biofilm oxidation states of minerals surface chemical changes associated with ennoblement and compositional variation of inclusion chemistry using advanced techniques of CLSM SPM Raman etc can help to validate the MMS mechanism of stainless steel. The presentation highlights this fresh look at this age-old problem using advanced chemical biological and metallurgical techniques and provides a deeper understanding of metal-microbe interactions on the localized corrosion of stainless steels.