Triple-line corrosion in high purity nickel

Abstract Electrochemical studies were conducted with high purity (99.999%) polycrystalline nickel in 2 N H 2 SO 4 and 0.3 M NaCl + 0.3 M Na 2 SO 4 solutions in order to assess the relative susceptibility of triple junctions to localized corrosion. The susceptibility was found to be strongly dependent on the specific crystallographic arrangement of crystals (as determined by electron channelling) at the triple junction, in accordance with Bollmann's criteria for a nodal balance of adjoining grain boundary dislocation arrays. Preferential triple-line corrosion was only evident at those junctions where these criteria were not satisfied. This enhanced susceptibility to localized corrosion (i.e. relative to adjoining grain boundaries and crystal surfaces) was examined in the light of the structural and chemical characteristics of these defects, and their influence on electrochemical surface film stability.

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