A single headed tube is an electric heating element, and due to its long-term use, its maintenance treatment is also necessary to ensure its extended service life. The repair and treatment of blackening of single ended pipes is often the most common maintenance method, which we refer to as blackening treatment. 
Simple steps for blackening treatment of single headed pipes:
The prerequisite for blackening treatment is to keep the surface of the heating tube clean and tidy. If there are impurities on its surface, it will not be conducive to blackening treatment.
The first thing B needs to do is to clear the organic matter on the surface, which is called degreasing treatment. Everyone should rest assured that degreasing treatment is easy to achieve here. Defatting treatment only requires the presence of degreasing solution. And degreasing solution is also easily available on the market. The requirement for degreasing treatment is to maintain an extremely high alkalinity of the liquid, with a stable pH value of around 13. The time requirement is approximately 30 minutes. After this treatment, the surface should be cleaned to remove impurities generated by chemical reactions. Cleaning must be done with clean water to ensure a high level of cleanliness on the surface of the heating tube.
After alkaline washing, it needs to be pickled. Because its surface not only contains alkaline organic matter, but also acidic organic matter. So acidic cleaning is also very necessary. A pH value of 3 is required for acidity, and the processing time should not exceed about 10 minutes.
Finally, formal blackening treatment will be carried out. Ph is guaranteed to be between 2-4. A time of 10 minutes is sufficient. After processing, proceed with cleaning.
The final step is to dry the single head tube. Drying is done to remove the water adhering to the surface of the single ended pipe. Finally, it's time to apply oil.