Mechanism of Stress-Corrosion Cracking.
Abstract
A study has been made of the corrosion and SCC of copper and alpha-phase Cu-Zn alloys in 1N ammoniacal solutions. Potentiostatic experiments confirmed that the corrosion process in non-tarnishing solutions is under concentration polarization, being controlled by the transport of the main cathodic species (cupric complex ions) to the surface, and established the reversible potential, the exchange current density and the Tafel slope for the main anodic reaction, copper dissolution. The conditions for tarnish formation and the nature of this cuprous-oxide layer were also studied. Potentiostatic studies of the potential dependence of SCC of annealed Cu-30Zn established that the critical potential for cracking corresponds to the reversible potential for copper dissolution. Moreover, SCC was shown to be predominantly intergranular in potential ranges where tarnishing occurs and transgranular in non-tarnishing ranges. These and other observations lend support to our view that inter- and transgranular SCC involve different mechanisms. The former is considered to occur by the film-rupture model. The mechanism of transgranular cracking has not been established, but fractographic and accoustic-emission studies of both Cu-30Zn and Admiralty Metal indicated that this form of cracking occurs by discontinuous cleavage on (110) planes. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1977
- Accession Number
- ADA042106
Entities
People
- E. Neville Pugh
Organizations
- University of Illinois Urbana–Champaign