Abstract
The reason why the spontaneous potential of titanium vibrates periodically to positive and negative directions in distilled or tap water, changing gradually to positive value with time, is that the positive and the negative ions accumulated in anodic (in pin holes of the oxide film) and cathodic (the oxide film) areas respectively, are not neutralized until they attain a certain amount in water. The spontaneous potential of titanium changes to a negative value with time in such solutions under natural aeration as HF>0.005%, HCl>10%, H2SO4>5%, H3PO4>30%, NH4F>0.01%. On the contrary, in such solutions as of HNO3, CrO3, K2Cr2O7 and K2MnO4 in acid solutions, Cu++, Fe+++, Ag+, it varies largely to a positive value and titanium is passivated. The corrosion rate of titanium in naturally aerated HF, H2SO4 or HCl solutions containing different oxidizing agents was measured.
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