Chemical composition of the aqueous solution within crevices on two different Ni-Cr-Mo-Fe alloys immersed in natural seawater was determined using a semiquantitative thin-layer chromatographic method. Active crevices were found to contain concentrated amounts of dissolved Ni2+, Cr3+, Mo3+, and Fe2+ ions. Propagation of crevice corrosion for the two alloys was determined from anodic polarization curves in model crevice solutions based upon stoichiometric dissolution or selective dissolution of alloy components. Both alloys 625 (UNS N06625) and C276 (UNS N10276) underwent crevice corrosion in the model crevice electrolytes. For the model crevice solution based upon selective dissolution of alloy constituents, the anodic dissolution rate for alloy 625 was higher than that for alloy C276. This trend was reversed for the model crevice solution based upon uniform dissolution of alloy constituents.

Subject
Constituents, Composition, Nickel based alloys, Molybdenum alloys, Dissolution, Crevices, Corrosion modeling, Crevice corrosion, Metals, Immersion, Aluminum alloys, Alloys, Electrolytes
Keywords:
alloy C276, alloy 625, anodic polarization, chromium, crevice corrosion, dissolution, iron, marine environments, molybdenum, nickel
NACE International
1997
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