Crystallographic anisotropy of corrosion rate and surface faceting of polycrystalline 90Cu-10Ni in acidic NaCl solution
Xuening Yi, Aili Ma, Lianmin Zhang, Yugui Zheng
Abstract
The orientation-dependent corrosion rate and surface faceting of polycrystalline 90Cu-10Ni in acidic NaCl solution was investigated statistically. A good linear relationship was found between corrosion rate and the deviation angle from the 〈1 1 1〉 direction of the grain. For the three principle low-index planes, the corrosion rates followed the sequence of (0 0 1) < (1 0 1) < (1 1 1). More interestingly, there is a clear correlation between crystallographic orientation and surface faceting of grains in 90Cu-10Ni. Grains orientated near the three principle low-index planes and the (1 1 2) plane exhibit four different types of submicron-scale post-corrosion morphologies, respectively. However, each type of the faceted structure is bounded by {0 0 1} planes which have the lowest corrosion rate, independent of the substrate grain orientation. This is supported by the crystallographic models and AFM topographic measurements. Current study provides a simple way to identify grain orientation by etching, and also promising solutions to optimize corrosion properties through tailoring surface texture and design micro- or nano-scale surface structure by controlled etching.