Stress corrosion cracking dealloying

Mechanisms of SCC. Crack initiation of EAC is complex and not well understood till now. Most of the SCC systems exhibit short initiation times ranging from minutes to weeks and cracking often occurs due to the change in the environment rather than to a very long initiation time. Stress-corrosion crack growth rates are usually 10 11 and 10-6 m s In systems such as stainless steels in chloride solutions, localized corrosion may create the local conditions prone to crack development, but it is still difficult to explain the initiation of the crack in the absence of localized corrosion in environmental conditions different from that of the crack propagation.95 It should be mentioned that dealloyed surface layers such as certain copper alloys in ammonia-containing solutions are believed to cause SCC.54... 

Moreover, it is evident that the intrinsic mechanical strength and fracture toughness of such nanoporous structures is low [55, 65]. Insofar, gross dealloying represents a serious form of corrosive deterioration. In addition to this, there is little doubt with respect to an association between dealloying and the stress corrosion cracking of certain alloys. 

K. Sieradzki, J.S. Kim, A.T. Cole, R.C. Newman, The relationship between dealloying and transgranular stress-corrosion cracking of copper-zinc and copper-aluminum alloys, J. Electrochem. Soc. 134 (1987) 1635-1639. 

Recent work by Jones et al. [80] has shown an enhancement of diffusion due to vacancies formed by anodic polarization. He has once again suggested that vacancies formed at room temperature by anodic dissolution are implicated in dealloying, embrittlement, and stress corrosion cracking. Specifically, divacancies are the species that migrate to the dissolving interface and enhance diffusion at that site. Other authors [87] have also recently returned to the vacancy enhemced mechanism for dealloying and SCC. 

Selective dissolution, where the less noble element dissolves selectively leaving behind a porous metal phase enriched in the more noble constituent, resulting in dealloying. The more common case is the selective dissolution of Zn (dezincification) from a-brass (Cu-Zn). Selective dissolution is in some instances associated with circumstances of stress corrosion cracking (SCC) [175]. 

Uniform, pitting, crevice, galvanic, dealloying, fretting, stress cracking, coating failure, corrosion product creep... 

---