Role of Films in Stress Corrosion Cracking and Hydrogen Embrittlement

Abstract

Stress corrosion cracking (SCC) is a term often used to describe the catastrophic fracturing of materials under the simultaneous influence of stress and exposure to an aggressive environment. This type of failure or fracturing is also referred to as environmentally assisted cracking, which emphasizes the important contribution of the environment on SCC. However, environmental cracking is also commonly used to describe all forms of cracking that are assisted by their environment, including liquid and solid metal embrittlement, hydrogen damage, and corrosion fatigue. To avoid confusion and the vagueness of the term environmental cracking, we use stress corrosion cracking in the classical sense to strictly apply to that form of cracking that incorporates a tensile stress with anodic dissolution to induce fracture. Furthermore, SCC is sometimes used to include classical hydrogen embrittlement (HE). While there are certain systems where SCC does appear to be dominated or assisted by HE, the majority of systems that display SCC cannot be simply classified as HE. Therefore, HE or, more correctly, hydrogen damage (HD) will be discussed as a separate mechanism.