Abstract
The effect of the optimization modes of the structure of polycrystalline copper based on grain boundary engineering (GBE) on its anodic behavior in NaCl solution was investigated. The samples were studied in the as-received condition, after recrystallization annealing and thermomechanical treatment (TMT) in mode I (TMT I) and TMT II mode. The surface corrosion results were observed using confocal laser scanning microscopy (CLSM). Surface observations showed that in as-received and recrystallized copper samples, metal oxidation occurs at random high-angle grain boundaries (RHAGBs). In the as-received samples, the surface defects formed during the technological processing and incoherent twin boundaries is also subjected to corrosion. Optimization of the structure in the TMT I and TMT II modes leads to a decrease in the role of RHAGBs as anodes and an increase of local corrosion in incoherent twin boundaries. In samples subjected to TMT II, with a further decrease in the fraction of RHAGBs, along with local corrosion of incoherent twin boundaries, the effect of grain surface corrosion increases. The rate of corrosion of the grain surface depends on the crystallographic orientation of the planes subject to corrosion attack and residual stresses in the structure. This leads to non-uniformity of the anodic process on the surface of the samples, which causes a faster dissolution of some large areas of the surface than others, which ensures different depths of their corrosion and the development of pitting. This is a crucial practical result of the observed anodic behavior of copper with a structure optimized based on the GBE. Although the corrosion rate of copper subjected to TMT II is an order of magnitude lower than that of recrystallized samples, there is a potential risk of pitting, which, unlike other types of corrosion, can spread very quickly.
Funding
1. The research was performed within the framework of Government Contract FWRW-2026-0002. -