Application of Scanning Vibrating Electrode Technique (SVET)to the study of weld corrosion

摘要

Welding of materials is one of the most common construction methods used throughout thernengineering community. Unfortunately this process disrupts the microstructure of the parentrnplate and, depending upon weld filler-rod chemistry, can result in major differences in bothrnchemistry and metallurgy of the welded joint. Furthermore welding produces internal residualrnstresses within the joint. These effects give rise to differences in electrochemical behaviourrnacross the welded joint, resulting in the formation of micro and macro-galvanic cells.rnScanning electrochemical techniques, which measure the micro-galvanic activity occurring onrnsurfaces immersed within conducting electrolytes, are therefore ideally placed to study therneffects of the welding process on the localised corrosion behaviour of materials. The outputrnsignal obtained during the SVET measurement is however significantly influenced by bothrnsystem parameters, e.g., solution conductivity, and operating parameters, e.g., sample-proberndistance, probe scan speed, vibration amplitude, etc.rnThis paper discusses both the influential parameters governing the SVET output signal, inrnterms of magnitude and resolution, and the application of the technique to a number ofrndifferent weld configurations. Conventional DC electrochemical techniques and optical/SEMrnobservation the weld corrosion is also presented for comparison purposes.