ABSTRACT
Before discussing this effort, it should be understood that stress corrosion cracking is not hydrogen embrittlement. (See Chapters 48 and 49.) It is possible to have hydrogen released during exposure to corrosive elements if a galvanic cell or differential aeration cell is created. This hydrogen can cause brittle failure, even in the absence of any significant corrosion. Hydrogen embrittlement will be encouraged if the fastener is exposed to hydrogen through acid cleaning and/or electroplating during manufacture. It can occur at hardness levels above Rc 35 in steel after the bolt is tightened to clamp the joint. It is interesting to note that H-11 steel has a high resistance to hydrogen embrittlement but not to stress corrosion cracking (SCC).
