Effect of temperature on CO_2 corrosion of dissimilar weld joint

To study the effect of temperature on CO₂ corrosion behavior of dissimilar weld joint, dissimilar weld joint of X70 pipeline steel and 2250 duplex stainless steel welded by metal inertia gas welding was used experimentally.Microstructure of X70/weld joint interface and CO₂ corrosion morphologies in weld joint at different temperatures were observed and analyzed.The results showed that dendritic structure appeared in weld joint.Narrow fusion zone and typeⅡboundary existed between micro-alloy steel and weld joint, and obvious concentration gradient of Ni and Cr elements was observed.Serious corrosion occurred in HAZ of micro-alloy at high temperature other than at low temperature.Corrosion product on surface of micro-alloy was shown loose while that on surface of weld joint was shown compact.Such different corrosion tendency of micro-alloy and weld joint was probably caused by the different ionic migration ratios as a result of different corrosion potentials of metals and different temperatures.