This paper reviews material selection for pumping aggressive media, with particular focus on media containing hydrogen sulphide. It describes a high-velocity test rig developed to track the corrosion forms that occur when such media are pumped.
Drawing on their own measurements and published data, the authors show that material choice depends largely on the composition of the medium - in particular the H2S content and the combination of H2S plus air.
Behaviour in seawater and chloride media
In pure seawater or pure chloride-containing media the differences between the materials examined are relatively small, and austenitic-ferritic (duplex) steels perform especially well.
Behaviour with hydrogen sulphide
With hydrogen sulphide present the differences between materials become large - reaching a factor of 10^4 at high H2S concentrations - and special materials are needed. Notably, the data supports adding copper to improve corrosion and erosion-corrosion resistance: in both 13%Cr and 25%Cr alloys, the copper-containing variants significantly outperformed the plain alloys. Ferralium® 255 is widely chosen for pump shafts for exactly this reason.
Finally, in media with high hydrogen sulphide contents the attack is initiated by pitting, even at very high flow velocities.
