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Mackinawite, a tetragonal iron sulfide mineral, is generally a major corrosion product when iron alloys are corroded by sulfate-reducing bacteria (SRB). The experimental database for the mineral indicates that on nongeologic time scales, mackinawite, if it forms at all in nonbiological corrosion, does so only under very reducing conditions and in the presence of sulfide activities not normally found in the biosphere or in ordinary corrosion testing.
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McNeil et al. (1990) studied this question.
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