The redness of stainless steel heat exchange tubes is mainly due to oxidation, ranging from light yellow and light blue to deep red and purple black in severe cases.
Therefore, the redness of the pipe needs to be solved by acid pickling and passivation, or by electrolytic polishing.
Before operation, personnel must wear acid resistant gloves/face shields. When diluting sulfuric acid, “acid in water” is strictly prohibited from reverse operation!
The steps of acid washing:
Degreasing → Acid washing (diluted with 10% industrial sulfuric acid, soaked at 60-80 ℃ for 10-30 minutes) → Water flushing → Neutralization → Passivation (generating dense oxide film).
Key: Use food grade acid wash solution (such as ID4008-T) to inhibit the precipitation of hexavalent chromium, dilute with water at a ratio of 1:2; After pickling, it must be fully passivated, otherwise it will accelerate corrosion.
Electrolytic polishing steps:
Removing the oxide layer through electrochemical dissolution is suitable for precision heat exchange tubes, but requires professional equipment operation.
If the redness persists, it is necessary to investigate the root cause of system overheating, such as abnormal combustion or insufficient flow.