A method for reducing the corrosion potential of steel vessels and piping used in nuclear reactors, in particular steel vessels and piping carrying high temperature water and/or steam which has a concentration of oxygen therein. A metal hydride is added to the water, the hydrogen of such metal hydride combining with oxidizing agents, typically oxygen, present in the water to reduce the concentration of such oxidizing agents. In the preferred embodiment the metal of the metal hydride is a metal that is capable of reacting with oxygen to form a substantially non-water soluble and substantially electrically insulating compound on the surface of the steel, and in particular is one that may react with and become deposited or incorporated into a pre-existing thin oxide film layer on the surface of the steel to thereby render such thin oxide layer substantially non-electrically conducting.