Copper sheet corrosion tester is a qualitative method to determine the corrosion of oil products, mainly to determine the presence of active sulfides and elemental sulfur that corrode metals. To determine the corrosiveness of fuel oil, a polished copper sheet of standard size is immersed in oil, maintained at the temperature and time required by the product specifications, and then removed and compared to the surface color of the non-oiled copper sheet. The corrosion level is determined according to the green, black, brown-black or steel-gray spots presented by the oil-immersed test piece.

The copper corrosion test determines whether the fuel contains active sulfides that can corrode metals. Sulfur compounds have a significant impact on the working life of the engine, with active sulfides having a direct corrosive effect on metals. All sulfur compounds have a direct corrosive effect on the metal. All the sulfur compounds in the cylinder after combustion are produced sulfur dioxide and sulfur trioxide, these sulfur oxides will not only seriously corrode the parts of the high temperature zone, but also with the cylinder wall of the lubricant reaction, accelerate the formation of varnish and carbon.