Effect of stress and surface finish on Pb-caustic SCC of alloy 690TT
G.B. Mazzei, M.G. Burke, D.A. Horner, Fabio Scenini
Abstract
The effect of surface preparation on lead-induced stress corrosion cracking (PbSCC) of Alloy 690 TT in Pb-caustic solution was investigated using C-rings manufactured from tubing that was either as-manufactured or polished. The surface deformed layer on the as-manufactured samples promoted the formation of an oxide, which reduced the number of sites for crack nucleation. Conversely, the polished surface developed crystallographic corrosion slots from which some of the cracks seemed to initiate. Advanced microstructural characterization complemented with stress analysis of the samples, suggested that the early stages of PbSCC are consistent with a film-rupture/slip-dissolution mechanism and influenced by de-alloying.