SEDL / STP / STP1049-EB / STP24063S

Role of Selective Dissolution in Transgranular Stress-Corrosion Cracking: Studies of Transient and Steady-State Dealloying in Copper-Gold Alloys

Flanagan, WF
Professor, graduate research assistant, graduate research assistant, and professor, Vanderbilt University, Nashville, TN

Lee, JB
Professor, graduate research assistant, graduate research assistant, and professor, Vanderbilt University, Nashville, TN

Massinon, D
Research staff, Institut de Recherche de la Sidérurgie Franchise, St. Germain-en-Laye,

Zhu, M
Professor, graduate research assistant, graduate research assistant, and professor, Vanderbilt University, Nashville, TN

Lichter, BD
Professor, graduate research assistant, graduate research assistant, and professor, Vanderbilt University, Nashville, TN

Pages: 14    Published: Jan 1990

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Abstract

Transgranular stress-corrosion cracking (T-SCC) was studied for disordered single crystals of Cu-25Au in 0.6 M sodium chloride in the potential range 0 to 600 mV (sce),over which exclusive selective dissolution of copper occurs and hydrogen generation is thermodynamically excluded. Under these conditions the strain-free anodic dissolution displays “passive” behavior below a critical (“transpassive”) potential, E^c. Massive dealloying occurs above this potential, leading to the formation of a gold sponge surface layer. On the other hand, scratching experiments established that transient dealloying occurs well below the critical potential, E^c = 430 mV, and straining electrode tests show that T-SCC also occurs in this same passive potential domain. In the passive domain, transient currents resulting from crack advance during T-SCC are shown to be analogous to transients observed during surface scratching in the same corrosive environment. It is also shown that dynamic straining enhances steadystate dissolution below E^c, thus indicating that crack-related deformation could lead to enhanced dissolution in the newly-formed crack. This has implications that affect our understanding of the renucleation process in TSCC.