Experts interpret the simple detection method of the metal spring after the black treatment

Appearance inspection: silicon-containing spring steel is reddish brown, and other spring steels are black. The oxide film should be uniform and dense, without spots, flowers on the surface, or red and dark deposits attached. Corrosion resistance inspection: wash the surface of the spring with alcohol or gasoline and dry it, soak it in a 2% copper sulfate solution for 30s, and wash it in water after taking it out. There should be no red spots on the surface.

　　The appearance of the phosphating film should be uniform, free from blooming, and the surface should be gray or dark red. There are two ways to check the corrosion resistance.

　　 (1) Copper sulfate solution spotting method The composition of the test solution is as follows:

　　0.5NCuSO4 solution 40ml

　　 10% NaCl solution 20ml

　　0.1HCL solution 0.8ml

　　 After mixing the 3 kinds of solutions, drop them on the surface of the spring cleaned with alcohol, and record the time when the red spots appear. The normal phosphate coating can be maintained for at least 1 min.

　　 (2) Salt water soaking method: Soak the phosphated spring in a 3% salt solution for 15 minutes, take it out and rinse it with water, and place it in the air to dry for 30 minutes. If there is no yellow rust, it is qualified. .