The corrosion behavior of welded stainless steel evaporator tubes was studied using electronic and optical micrography. The presence of roughness, surface faults, and crevices in the stagnant condition of the fluid and Cl- ions, promoted corrosive attack with many pits. Once this corrosion process starts, it goes on with an autocatalytic mechanism of occluded cell until tube perforation occurs. To improve the corrosion resistance of the tubes, the welds should be cleaned using paste with pickling action with HNO3 and HF, and then polished. A treatment with 10% HNO3 should follow to further improve the performance of the passive layer. The use of titanium-rich stainless steel is also recommended to increase its resistance to localized corrosion.
Failure avoidance: Failure of welded stainless steel evaporator tubes
Rossi, Stefano
1998-01-01
Abstract
The corrosion behavior of welded stainless steel evaporator tubes was studied using electronic and optical micrography. The presence of roughness, surface faults, and crevices in the stagnant condition of the fluid and Cl- ions, promoted corrosive attack with many pits. Once this corrosion process starts, it goes on with an autocatalytic mechanism of occluded cell until tube perforation occurs. To improve the corrosion resistance of the tubes, the welds should be cleaned using paste with pickling action with HNO3 and HF, and then polished. A treatment with 10% HNO3 should follow to further improve the performance of the passive layer. The use of titanium-rich stainless steel is also recommended to increase its resistance to localized corrosion.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione
