The effect of ultraviolet (UV) illumination on the NaCl-induced atmospheric corrosion of pure zinc was investigated in this work. UV illumination affects the atmospheric corrosion morphology and corrosion rate of zinc. The NaCl-induced atmospheric corrosion rate of zinc increases significantly under UV illumination, which can be attributed to the photovoltaic effect of the corrosion products with semiconductor properties. The photoinduced electrons and holes, which are generated by the corrosion products with semiconductor properties under UV illumination, participate in the corrosion reactions and thus affect the atmospheric corrosion rate of zinc.

The effects of relative humidity on the initial atmospheric corrosion of zinc during drying of chloride-contained absorbed thin electrolyte layer was investigated by mass loss, scanning electron microscopy (SEM), cathodic polarization curves, pre-Tafel polarization curves fitting method and electrochemical impedance spectroscopy (EIS). The results showed that the zinc corrosion rate decreased with increasing relative humidity in the first 2 h. After 72 h of exposure, the corrosion rates of zinc were ranked as: 75% RH < 85% RH < 97% RH. And the morphology of corrosion products at 75% RH appeared more compact than that of 85% and 97% RH.Zinc is widely exposed to the atmosphere, particularly in the form of steel coatings and paint pigments designed to protect underlying metal against corrosion by the sacrificial loss of zinc because of its relatively lower corrosion potential (E corr ) in the electrochemical series. Substantial research on the corrosion of zinc materials has been performed in field exposure and controlled laboratory environments. [1][2][3][4][5] Indeed, the importance of zinc is enhanced especially in coastal regions, where airborne salinity more significantly affects the degradation of structures than pollution with reduced industrial pollutants. 6 Deposition of airborne salinity on metal components can cause them damage and reduce their service life.Chloride deposition is a major contributor to increased atmospheric corrosivity in marine environments. 7 Oceans provide a source of chlorine in the form of marine salt (e.g., NaCl and MgCl 2 ), which can be directly emitted by the ocean or formed by turbulent ocean states and surf action and transported inland predominantly by coastal wind patterns. 2 Atmospheric corrosion can be accelerated by the deposition of marine salts. Lindström et al. 3 reported that the zinc mass loss of samples covered with sodium chloride particles remains constant in the presence of CO 2 regardless of temperature; by contrast, the strong temperature dependence of metal loss on CO 2 -free air was observed. This study showed that CO 2 is important for zinc corrosion. In fact, sodium chloride is the main stimulator of atmospheric corrosion in metals, and a substantial amount of research on this type of corrosion has been done. 2,4,6 Sodium chloride is hygroscopic; thus, atmospheric moisture may condense and form droplets and/or adsorbed thin electrolyte layers (ATELs) containing chloride ions when the temperature drops and relative humidity (RH) rises. By contrast, increases in temperature and/or drops in RH lead to the evaporation of sodium chloride electrolyte (drying) and increase in chloride concentration in the ATELs. 8 The diameter and thickness of droplets and/or thickness of ATELs also change with variations in the ambient temperature and RH.Atmospheric corrosion under droplets has been extensively studied. 1,[9][10][11][12] In general, when droplets on a metal surface evaporate, they form thin electrolytic films and drastically increase the metal corrosion rate. Sinc...