The effect of nanotwins on the corrosion behavior of copper

Ultrafine grain sized (∼0.4 μm) Cu samples having different fractions of nanotwinned grains (∼5%, ∼60% and >90%) were synthesized in order to evaluate the effect of the nanotwins on the overall microstructure. It was observed that nanotwins have a fundamental effect on altering the grain boundary network and texture of sputtered Cu samples. Increasing the fraction of nanotwinned grains increases both the fraction of special (Σ3) grain boundaries and the intensity of the {1 1 1} texture. Polarization and immersion corrosion tests using a 3.5% NaCl solution were performed on the nanotwinned Cu samples and compared to microcrystalline Cu (grain size ∼ 9 μm). It was found that highly nanotwinned Cu (nanotwinned grains > 90%) had the highest corrosion resistance among all samples, which is attributed to its unique grain boundary network and {1 1 1} texture. In addition, the passive layer formed on highly nanotwinned Cu during corrosion achieved the highest pitting resistance when compared with the other samples.