Stress Corrosion Cracking of Titanium: Some Surface Chemical Reactions in Methanol and Carbon Tetrachloride

The vapor-phase interaction of methanol and carbon tetrachloride with thin films of titanium, evaporated under high vacuum conditions was studied. At temperatures in the range 120 to 150 C (248 to 302 F), methanol reacted readily with titanium to form titanium methoxide, resulting in a gradual disappearance of the film. Prior oxidation of the titanium surface or addition of water to the methanol prevented this reaction. Using mixtures of methanol and perdeuteromethanol and of carbon-13 and oxygen-18 enriched methanol, it was demonstrated that at this temperature, reaction on a clean titanium surface involved only cleavage of the alcoholic O-H bond. Addition of hydrogen chloride to methanol enhanced the rate of dissolution of titanium in proportion to the amount of hydrogen chloride present. Carbon tetrachloride reacted with titanium in the same temperature range to form titanium chlorides. These direct reactions between metal and organic environment are discussed in relation to the stress corrosion cracking behavior of titanium.