Effect by Buffing Treatment on Intergranular Corrosion（IGC） Property of 690 Alloy Tube for Heat-exchanging Service

The 690 alloy tube for heat-exchanging service as aging-treated is subjected to the IGC test with the soaking（65%HNO₃）method before buffing，and the electrochemical（EPR）method after buffing in order to investigate how the buffing process affects the IGC property of it. The test result shows that with the soaking （65%HNO₃） method，little effect is found，while with the electrochemical（EPR）method，such a fact is identified that along with increasing of the buffing frequency，the activation current strength is reduced and going to be finally stabilized. Also identified via the test is that the surface roughness level of the buffed material plays a major role which affects the electrochemical corrosion property of the tube.