The pitting corrosion of stainless steel in neutral chloride media at 70°C was prevented by applying cathodic current in its passive region. The protective potential range of -0.6- -0.4V, vs. SCE and its required cathodic current density of 8μA/cm² were determined by measurements on polarization and potentiostatic dissolution current change in long period.
This method was applied to a chemical plant and successful in preventing its pitting.

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An unusually rapid corrosion leakage occurred in an underground hot spring water pipeline in a volcanic area within about half a year after its laying. The field survey and laboratory tests showed that the abnormal corrosion of the hot water pipeline would have been caused from original macrocorrosion cells, large difference in resistivity due to the difference of moisture contents between upper and lower soil parts round the hot pipe and formation of magnetite on the pipe surface because of the high temperature and the alternative dry and wet condition. As for the protective measures epoxy coating and cathodic protection were studied, and their combination appeared very effective.

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Effects of the addition of molybdenum on the corrosion resistance of various alloys were investigated in maleic acid solution. The results were as follows.
(1) The critical current density of Fe-18% Cr alloy is depressed by the addition of molybdenum and this effect is remarkable when molybdenum content is 2%.
(2) Molybdenum added to Fe-18% Cr-(8% and 12%) Ni alloys has a favorable effect for the reduction of the active dissolution. But this effect is not so much as on Fe-18% Cr alloy.
(3) The polarization behaviour of Fe-(8% and 12%) Ni alloys containing molybdenum does not differ too much from that of Fe-Ni alloy.
(4) When Fe-18% Cr and Fe-18% Cr-Ni alloys contain 2% Mo, the corrosion resistance increases remarkably.

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