The effect of surface treatment of titanium on hydrogen absorption was investigated.Surface treated titanium specimens prepared by polishing, anodizing and air oxidizing were immersed in 0.5-6%HCl solutions at the temperature range of 70C to 250C. After immersion, the weight loss, hydrogen content and oxide film thickness of three specimens were measured. As a result, it became clear that anodizing did not reduce hydrogen absorption of titanium because titanium oxide film formed by anodizing had dissolved away in dilute HCl solutions for short time but air oxidizing specimen was stable in this solution for long time and so prevented to hydrogen absorption of titanium.These results of laboratory tests corresponded to the results of field tests conducted in hot molten urea and reducing acid solution at high temperature.

The corrosion resistance of titanium exposed in nitric acid vapor is Using this testing apparatus, the corrosion rate of titanium in the condensed zone was 0.37 mm/year (1 .1 7x I 0-11 m/s), greater value than those in any other zone and general corrosion occurred. Moreover, the corrosion rate in the liquid zone was less than 0.01 mm/year(3.17x 10-13 m/s) and this rate was regarded as the perfect corrosion resistance. That is because of concentrated soluble titanium ions in the solution acted as a corrosion inhibitor.In the case of 304Lstainless steel, the corrosion rate was 4.5 mm/year (1 .4 x I 0-10 m/s) in the liquid zone at the highest value, and the intergranular corrosion occurred. On the other hand, the rate in the condensedsolution was small to be 0.095 mm/year (3.01 x 10-12 mls).

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Hydrogen absorption of Ti-Pd alloys in deaerated and aerated hydrochloric acid solutions where Ti-Pd alloys are in the passive state were compared with that of pure titanium. In particular, the role of palladium in the hydrogen absorption of Ti-Pd alloy was discussed. The results obtained are as follows;

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