The super-austenitic grade Alloy 35Mo (UNS N08935) has excellent corrosion resistance and mechanical properties for harsh corrosion environments within refinery and petrochemical industry, e.g. shell-and tube heat exchangers in sour water services and seawater cooling. The process fluids in the heat exchangers can be highly corrosive and correct material selection is critical for reducing corrosion failures, maintenance, and repair costs.

In this paper, different corrosion testing methods and results of Alloy 35Mo will be presented and compared with common existing corrosion resistance alloys (CRA) in refinery and petrochemical industry. The corrosion test methods cover pitting and crevice corrosion resistance, and setups approximating the corrosive condition in a hydroprocessing reactor effluent air cooler (REAC) in a refinery. The latter test will be carried out in hydrogen sulfide (H2S) dominated environments with different ammonium bisulfide (NH4HS) concentrations. The results show that Alloy 35Mo is an excellent alternative to the established corrosion resistance alloys in refinery and petrochemical industry.