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The corrosion reaction of iron wire and the effect of tensile stress on the reaction were investigated in a hydrocarbon oil and hydrocarbon solution containing sulfur compounds using the hot wire method. The corrosion rate followed the parabolic law after an initial stage in white oil and elementary sulfur solutions. The diffusion of reactant through the formed film on the iron wire is considered to be the rate-determining step. Generally the tensile stress applied to iron wire accelerated the corrosion reaction. It seems to be the effect of stress-induced heterogeneity in the formed film. Corrosion observed in the case of benzyl mercaptan solutions was significantly higher than other sulfur compounds, and the corrosion rate followed linear relationships. In this case the effect of tensile stress was not observed clearly because of high corrosion rate. With dibenzyl disulfide the corrosion did not follow any of the known relationships. To understand the mechanism further, similar experiments were conducted in nitrogen atmosphere. Corrosion occured severely on iron surface in nitrogen atmosphere as compared to air. The reaction products on the wire surface were analysed by X-ray diffraction method to deduce the corrosion mechanism.

The rusting of ball bearings caused by vapour from the insulating varnish in electric motors was investigated by measuring the corrosive acid vapour using ion chromatographic analyser. It was found that formic acid evolved depending on the kind of varnishes, and that the amount had good correlation with the extent of rusting of bearings tested in a relative humidity of 70 percent. Based on the limit of formic acid present, a quantitative evaluation of varnish-induced rusting and classification of varnishes are presented.