CORROSION OF WELDED STEEL IN HUMID AND CHLORIDE ENVIRONMENT UNDER ACCELERATED CONDITIONS

Abstract

The present study has been conducted to observe the corrosion behaviour of mild steel processed by MMAW of as-welded and post weld heat treated specimen exposed to purely humid environment under accelerated conditions, with regard to electro-potential values of weld moetal, heat affected zone and base metal. The test was conducted for exposure period of 10 and 20 days. In the study rutile and basic electrodes are used for welding of mild steel plates. Metallographic examination of specimens is also carried out and corrosion behaviour is also related with microstructure. Graphs of V.H.N. vs distance from weld centre time also plotted. The electropotential values are measured with reference to saturated colomel electrode. The electro-potential values of weldmetal are more positive as compared to HAZ hence weld metal corroded more than HAZ. In the same way HAZ is more electro-positive than base metal and hence HAZ corroded more than base metal. The corrosion rate of post weld heat treated specimen is less than as welded specimens due to homogenity of microsture in post weld heat treated specimens. In the comparision of corrosion rate, the corrosion rate in humid environment under accelerated condition is found less than chloride environment under accelerated condition. But it is greater than corrosion rate in chloride environment under normal conditions