How to deal with the blackening of the surface of stainless steel polished tubes

Stainless steel polished tube has good corrosion resistance, heat resistance, low-temperature strength and mechanical properties, and good hot processing properties such as stamping and bending. It is widely used in equipment in seawater, chemical, dye, papermaking, oxalic acid, fertilizer, and other production equipment. However, the question is how to deal with the blackening of the surface of stainless steel polished tubes. Below, we have sorted out some reasons and treatment methods for the blackening of the surface of stainless steel polished tubes.

Generally speaking, good stainless steel polished tube products will not have this situation. If the surface of the tube turns black during long-term use, this is because the stainless steel polished tube produces a layer of oxide film under the action of air. The role of the oxide film is to protect the metal inside the stainless steel from continuing to be oxidized. This oxide film does not need to be wiped off deliberately, and it does not damage the tube. Stainless steel polished tubes of different materials have some differences in element content, so the color of the oxidized film will also be different, but it does not affect the tube. If you think this is not beautiful, you can do a polishing treatment.

If the surface of the stainless steel polished tube turns black after welding, this is caused by insufficient purity of the welding gas or high-temperature oxidation. The following three methods will teach you how to avoid such things.

1. Increase the purity of the argon used in the welding of stainless steel polished tubes to pure argon. From the outer surface of the tube alone, pure argon is significantly brighter than ordinary argon welding.
2. The argon gas on the back should be well protected. The stainless steel polished tube must be protected on the back after welding. Otherwise, high-temperature oxidation will cause the weld layer on the back to oxidize and produce defects. The back weld is polished like slag, so after protection, it can effectively prevent back oxidation.
3. You can apply a back protective agent on the back, which is a kind of agent that can save argon protection. Apply a thickness of about 1 mm, and then form a thin film on the back when welding on the front to form a protective layer.

If you have found that the weld marks of the stainless steel polished tube are black, you can use pickling passivation paste to clean it, that is, use acid to corrode the black oxide layer on the surface, and then rinse it with clean water.