Some discussions about the mechanism of the unexpected severe impingement corrosion of condenser tubes were made in relation to hydrotalcite. It was elucidated experimentally that hydrotalcite is the initial corrosion product of Aluminum Brass in the natural sea water. Even if iron rich protective films are formed on hydrotalcite, they will be broken quite easily by the collision of foreign bodies with smaller energy in the sea water. This will increase the possibility of corrosion. The most important countermeasure is to supress the initial corrosion of condenser tubes by the effective ferrous ion dosing and to prevent hydrotalcite formation. It was pointed out that more attension should be paid to hydrotalcite from the standpoint of corrosion engineering of condenser tubes.

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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 70°C to 250°C. 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.

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Stress corrosion cracking of hydrogenated austenitic stainless steels were investigated in H₂SO₄-NaCl solution. The specimens used were exposed to 280 atm hydrogen at 400°C for 16 hours. The time-to-fracture of hydrogenated Type 304 steel was shorter than that of hydrogen-free ones in weakly corrosive solution and was longer than that of hydrogen-free ones in strongly corrosive solution. And that of hydrogenated Type 316 steel was shorter than that of hydrogen-free ones even in strongly corrosive solution. The susceptibility of stress corrosion cracking of hydrogenated Type 304 steel decreased under the catholic charging. This suggests that the stress corrosion process of this steel is active path corrosion. The self-activation time of Type 304 and 316 steels in H₂SO₄ solution became shorter by hydrogenation, and cold working increased this trend. In immersion test in FeCl₃ solution, Type 304 and 316 steels increased the susceptibility of pitting corrosion by hydrogenation. From these results, the change of stress corrosion cracking susceptibility of hydrogenated austenitic stainless steels might be produced by passive film destabilization and anodic activation of stress induced martensites.

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Some abstracts of the regulations, standards and related specifications for corrosion control mainly in Japan are described. Some important examples of the foreign reqgulations, standards and specifications for corrosion control are also summerized.

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