316l corrosion
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Dear experts, the image shows the corrosion state of 316L steel. The medium involved is 88% sulfuric acid, carbon monoxide, and isobutylene, with a temperature of around 80 degrees. What could be the cause of this corrosion?
Previously, when the furnace was turned on, its surface was smooth; I think this situation is caused by corrosion, but I can’t find the reason
88% sulfuric acid at around 80 degrees Celsius – its corrosivity is extremely high; 316L steel is not suitable for use in such conditions. At least an ECTFE lining is necessary.
Mainly, the pressure inside the furnace is too high, around 6 MPa
In fact, pressure is not the main factor. Someone upstairs mentioned that 316L actually does not have good corrosion resistance to sulfuric acid. As can be seen from the graph, there are weak acids accounting for less than 23%, as well as strong acids accounting for over 85%. 316L is prone to corrosion at high temperatures, and this tendency becomes more pronounced as the temperature rises. Sulfuric acid at around 80°C is well suited for PTFE pipes.
It is clearly corroded; in cases like this, a chromium-nickel-molybdenum-copper alloy is more suitable
High pressure is not a problem. The outer shell must be pressure-resistant; the lining or coating with ECTFE or PFA provides corrosion protection.
In our factory, 316L pipes are used for 98% concentrated sulfuric acid at room temperature
When the pressure is high, it is necessary to consider the pulling force between the anti-corrosion layer and the main body under such high pressures; the coating cannot withstand such high pulling forces. As for my equipment with a non-metallic lining at 6 MPa, I have yet to see any examples of it