Study on the Mechanism of the Photoelectrochemical Effect on the Initial NaCl-Induced Atmospheric Corrosion Process of Pure Copper Exposed in Humidified Pure Air

The mechanism of the photoelectrochemical (PEC) effect of the corrosion products with semiconductor properties on the initial NaCl-induced atmospheric corrosion of pure copper was studied in this work. The effect of UV illumination on the initial NaCl-induced atmospheric corrosion of pure copper was quantitatively studied using microgravimetry. Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy were used to identify the corrosion products and corrosion morphologies. Mott-Schottky methods were used to characterize the semiconductor type of the corrosion products. The photoinduced variations of the open circuit potentials, current densities, i-V curves and the polarization curves were used to analyze the PEC effect of the corrosion products with semiconductor properties on the corrosion of copper. UV illumination significantly increased the NaCl-induced atmospheric corrosion rate of copper. The photoinduced electrons did not transfer to the copper substrate, on the contrary, the photogenerated holes captured the electrons from the copper substrate, thus accelerating the atmospheric corrosion process of pure copper. The detailed influencing mechanism of the PEC effect on the NaCl-induced atmospheric corrosion of copper was suggested in this paper.