Hydrogen

Element, chemical symbol H. A colorless gas, which is strongly absorbed by many metals. Widely used for reduction of metals from their oxides. Hydrogen may cause several types of defects in steel, and its presence in the metal is almost never beneficial. In steel, the three main sources of hydrogen are steelmaking, pickling and electrocoating and steps should be taken to remove any hydrogen thus introduced (e.g., baking after pickling and coating). This element may also cause embrittlement in ETP copper by its reaction with copper oxides. See Hydrogen Atmosphere, Hydrogen Embrittlement.