Issues regarding the corrosion of boiler convection tubes
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Our 60-ton waste heat boiler has been in use for over five years, and the latest leakage was particularly severe; a large amount of powdery rust was found in the lower header of the economizer, which is likely due to oxygen corrosion. However, the lower manifolds of each convective tube contained not only powder-like substances but also strip-shaped and flake-shaped materials; it’s unclear whether this corrosion is caused by water. I checked the water source and there were no issues, and the other air-blown boiler that uses the same water as it also worked fine. I also consulted some experts; some said it was just iron sheets, and there was no corrosion at all. But it was checked and opened for maintenance half a year ago, and there were no problems. No reason can be found at all……
It is recommended to conduct a scale sample analysis first to determine what substances these scales consist of.
The analysis results showed that the sample contained 2% calcium phosphate, indicating subsurface corrosion. How does underscale corrosion occur?