There are specific national standards for testing the effects of surface treatments such as degreasing, rust removal, phosphating, and passivation. In addition to using professional methods for quantitative detection, it can also be easily judged by some simple and practical methods.
In order to judge whether the steel surface is cleaned after surface treatment such as degreasing and derusting, the simple method is to immerse it in water, then take it out and observe whether the water film formed on the surface is continuous. If the water film is complete and continuous, it means it has been cleaned. clean. Because the cleaned steel surface is hydrophilic, it can be completely wetted by water. When there is dirt on the metal surface, there will be a water-cut area that is not wetted by water. However, it should be noted that the oxide film on the steel surface cannot be detected by this method. Therefore, the copper sulfate method is often used to test the cleanliness of the steel surface and the effect of removing oil and rust. Brush the copper sulfate solution on the surface of the treated steel plate, since the iron can replace the copper in the copper sulfate, so a layer of metallic copper will adhere to the surface of the steel plate. Therefore, the part where the rust is completely removed will be the color of metallic copper, while the part where the oxide scale remains is dark. The rust removal effect can be judged from the color difference. Also dip the steel plate into the acidic copper sulfate solution, take it out and rinse after 1 minute, if a complete copper film is replaced, it means that the steel surface is clean and free of oil, otherwise it means that there is residual oil.
To check the degreasing effect, you can also wipe the steel surface with white cloth, cotton or filter paper to see if they are stained with oil or dirt. If they are clean and free of dirt, it means that the cleaning and degreasing effect is good.
The ultimate goal of surface treatment is to obtain a good coating effect, so it is the most practical to test its coating effect. The specific method is to paint the surface-treated sample as required, and then immerse the painted sample in water for 24~48 hours. If the surface treatment is not good, the coating will peel or even fall off.