This paper reports on the performance of Electron Beam Welded (EBW) low alloy steel AISI 4140 and stainless steel AISI 304 in air as well as molten salt environments of Na2SO4-60%V2O5 and K2SO4-60% NaCl at 650°C. The corrosion kinetics has been established by thermo-gravimetric technique during the initial stages. In this work, X-ray diffraction, scanning electron microscopy/energydispersive analysis and electron probe micro analysis techniques were used to analyze the corrosion products. It is well observed from the experimental results that the weldments suffered accelerated corrosion in K2SO4-NaCl environment and showed spalling/sputtering of the oxide scale. Furthermore, corrosion resistance of weld interface was found to be lower than that of parent metals in molten salt environment. It is also inferred from the results that NaCl is the one of the maincorrosive species in hot corrosion, involving mixtures of K2SO4-NaCl and which is responsible for internal corrosion attack. © 2013 University of Manchester and the authors.