A urea plant, operating on ammonia and carbon dioxide (CO 2 ) gases, had to be shutdown due to corrosion in the intercooler and aftercooler of its CO 2 gas cleaning circuit. Extensive general corrosion of AISI type 304 stainless steel parts, such as sealing strips, fins, demisters and the shell, of these two components which were in contact with the duplex stainless steel tubes, caused the shutdown of the fertiliser plant within 6 months. Investigations of the corrosion products by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) techniques showed the presence of carbon and ammonia based compounds, thus suggesting the role of ammonia and CO 2 gases, or the product of their reactions, in the corrosion of type 304 stainless steel. Electrochemical polarisation studies showed that duplex stainless steel possessed a more positive open circuit potential and a nobler critical pitting potential than type 304 stainless steel thus confirming that the corrosion of type 304 stainless steel was caused by the galvanic action with the duplex stainless steel heat transfer tubes. Hence, it was recommended that (i) the same material (type 304 stainless steel) be used for all parts of the intercooler and aftercooler to avoid galvanic corrosion, (ii) condense water carried over by CO 2 gas by cooling it to low temperatures immediately after it comes out from the scrubber, (iii) slight modification of the process to add up to 0.8% oxygen in the CO 2 gas before entry into the intercooler, which will help in retaining/formation of an effective passive film on type 304 stainless steel.