Effect of welding on the corrosion behaviour of a highly alloyed austenitic stainless steel UNS N06027 in polluted phosphoric acid media

The objective of this work is to study the effect of welding on the corrosion resistance of the austenitic stainless steel Alloy 59 (UNS N06027) as well as the galvanic corrosion generated by the base/weld pair estimated from the polarisation curves according to the mixed potential theory. The materials have been exposed to polluted phosphoric acid at several temperatures. The microstructure of the samples was studied by SEM and EDX analysis. The results show that the welding process shifts the corrosion potential values to more anodic potentials. The corrosion current densities and the passive current densities also increased by the effect of welding. This effect is aggravated with the increase in temperature. Open circuit potential values were located in the passive zone of the potentiodynamic curves, which means that the materials passivated spontaneously.The galvanic corrosion of the pair is not severe in the studied conditions. The ratio between the galvanic current density of the pair and the corrosion current density of the uncoupled anode is less than 5, which implies compatibility of the members in the couple.