343 is a highly effective anti-tarnishing agent used for gold and silver plating. For silver plating, a 5% K2S test for 3-20 minutes does not cause any discoloration (time depends on the thickness of the silver plating under 25℃), and no discoloration occurs after 10 minutes at 260℃. Potassium sulfide is available in the market with different concentrations, such as 45%, 50%, and 98%, as well as an unknown concentration for blackening. To ensure the accuracy of the potassium sulfide test results, it is recommended to use the 98% concentration. For gold plating, there is no corrosion after a 72-hour salt spray test.
