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During long-term use, the surface of some polished stainless steel tubes may turn black. This is common in the oxide film formed under air contact. Although this oxide film may affect the appearance, it does not damage the material itself, but plays a protective role to a certain extent. Due to different material ratios, the color of the oxide film formed by different types of stainless steel may also be slightly different.
If the user has high requirements for the surface aesthetics, it is recommended to polish it to restore its original finish.
On the other hand, if the surface turns black during welding, it may be caused by high-temperature oxidation or insufficient argon purity. In this regard, the following measures can be taken:
1. Increasing the purity of welding argon can help reduce oxidation at the weld.
2. Argon protection on the back of the weld can prevent the internal weld layer from being oxidized by high temperature.
3. If the operating conditions are limited, a welding back protective agent can also be used to form a protective layer to isolate the air.
After the weld turns black, it can also be cleaned with pickling passivation paste. This method can effectively remove the black oxide layer, and then rinse with clean water to restore the surface brightness.
MTSCO always insists on providing customers with high-quality, cost-effective products and professional services. Our main products include stainless steel polished pipes, seamless pipes, welded pipes, BA/AP polished pipes, pipe fittings, flanges and various forgings. Whether you have any product requirements or technical questions, please feel free to contact us, we will provide you with support and assistance as soon as possible.
