CORROSION BEHAVIOUR OF DISSIMILAR WELD

Abstract

Investigations have been carried out to find the corrosion behaviour of base metals (low alloy steel and austenitic stainless steel), weld metals (ER308 and ER309L), heat operated zone region and dissimilar welded specimens processed by GTAW under static and accelerated condition in 3.5M NaCl solution. The tests have been conducted for 2 days, 4 days and 6 days under accelerated condition and 25 days, 30 days and 35 days for static condition. Metallographic examinations of the specimen have been also carried out. Graphs of V.H.N. vs. distance have been plotted. Tensile test and Impact V-notch test also have been carried out. Corrosion rate of the welded specimens are higher than the base metal specimens and specimens that contain heat affected zone region under both static and accelerated condition due to galvanic corrosion of dissimilar welds. In intergranular corrosion test, weight loss is maximum for base metal heating at 675°C and lowest for welded specimen without heating in the first 12 hours test and also during second test of 24 hours duration, pits are formed on the whole surface of all the specimens, so weight loss has increased as compared to first 12 hours test. Micro structures are also observed after test