A joint action mechanism of anodic dissolution and hydrogen entrance during environment cracking

Abstract

Environment sensitive cracking refers, mainly, to stress corrosion cracking (SCC) and corrosion fatigue (CF) in aqueous solutions. Presently, the research devoted to environment sensitive cracking primarily focuses on SCC. Compared to SCC, the research of CF is relatively rare. There are some similarities between SCC and CF crackings; although, they are two different kinds of environment sensitive cracking. It is suggested that static stress is a special function of cyclic stress, or cyclic stress is a special function of static stress; therefore, the mechanisms of SCC and CF can be substituted in many cases. There are some limitations to explain crack growth in aqueous solutions using previous SCC or CF mechanism. For example, hydrogen embrittlement (HE) is widely accepted as the principle cause of SCC or CF in high strength steels. Anodic dissolution (AD) is another process believed to propagate cracks by stress assisted corrosion in low strength steels, but a problem arises for the researchers because of their inability to explain the mechanisms of crack growth for high strength steels. Fracture theory of surface film is a successful explanation of crack growth in filmed systems; however, it is not supported in an acidified solution. Although many researchers have triedmore » to propose universal mechanisms of environmental cracking, they have not procured a unified theory. In this paper the authors propose a joint action mechanism of anodic dissolution and hydrogen entrance during environment sensitive cracking based on the electrode reactions at the crack tip, and they also propose a remedy for the weakness of previous mechanisms.« less