The objective propels the analysis of potential microbiological influenced corrosion(MIC) in stainless steel as a function of the resistance of stainless steel to localized corrosion as evaluated by conventional test methods.It is reasonable to explore whether or not all stainless that are equally susceptible to MIC.This is because of the wide range of pitting and crevice corrosion resistance available in stainless steels. There are many test which evaluate the resistance localized corrosion but the ferric chloride (ASTM G-68) method is one of the most widely used.This test produces acidic oxidizing condition similar to those produced by iron and manganese oxidizing types of bacteria. and as there may be some relationship between ferric chloride test data and the metal oxidizing types of bacteria. Ferric chloride testing has been used to determine pitting temperature (CPT) and critical crevice temperature (CCT) for corrosion resistance stainless steel and nickel based alloys (TATNAIL,1981).Ranking the materials by this and similar test has been helpful in making successful material selections. The correlation between the ferric chloride and a stainless steel chemical composition has been demonstrated in fig.1.Representing critical temperature are summarized on a range of stainless steel table.1, types 304 and 316 have relatively low resistance as indicated by low critical temperature,904L has moderate resistance and 6% Mo stainless steels have very good resistance, A study of Kovach and Raymond suggests that positive correlation exist between ferric chloride test and service experience(KOVACH,1995).
(1) Microbial activity almost certainly has been present in many of this applications,therefore this correlation suggest that high performance stainless steel are significantly more resistance to MIC than the standard grades.
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