Hydrogen damage in carbon steel is assumed to be caused by corrosion hydrogen. Theoretical considerations indicate the equilibrium partial pressure of hydrogen at the carbon-steel surface, exposed in pure water at high temperature, is significantly high. Acidification of the water further increases the partial pressure of hydrogen by large values. Under normal pure conditions a major part of the corrosion hydrogen may readily be released to the coolant. Contamination of the reacting magnetite surface with strong catalytic poisons could, however, block the escape of hydrogen with the coolant. In this event hydrogen could be forced into the steel at high pressure. Free-energy considerations indicate the resultant decarburization of the steel and the partial pressure of methane formed could readily jeopardize the integrity of the material.

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