Photo-corrosion of different metals during long-term exposure to ultraviolet light

The effect of ultraviolet light on the corrosion rates of different metals was studied in two separate investigations. Metal samples were immersed in a flowing fresh water discharge stream for either three or five months under both ultraviolet (UV) light and dark conditions. Weight-loss results demonstrated that pure zinc, carbon steel, aluminum 6061 (UNS A96061), pure copper, and pure silver all experienced photo-corrosion, that is, a greater weight loss under exposure to UV light vs in the dark. Titanium, zirconium, Type 304 (UNS S30400) stainless steel, and pure nickel showed a weight gain during immersion, but the cause of the weight gain was uncertain. Pure nickel and Al 5052 (UNS A95052) did not show any reproducible trend. Zirconium, titanium, and brass showed a photo-effect in one investigation, but not in. the other. The photo-corrosion is explained with models based on the photo-voltages measured on corroded metal samples.