Simple detection method after the metal spring is blacked out

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. After taking it out, wash it in water, there should be no red spots on the surface.

The appearance of the phosphate coating 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) The composition of the test solution of the copper sulfate solution spot method is as follows:

40ml 0.5NCuSO4 solution

10%NaCl solution 20ml

0.1HCL solution 0.8ml

After the three solutions are mixed, drop them on the surface of the spring cleaned with alcohol, and record the time when the red spots appear. The normal phosphating film can be maintained for at least 1 minute.

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