This paper summarizes results of Phase II of a joint industry program (JIP) that addressed ammonium bisulfide (NH4HS) corrosion. This phase of the program was focused on NH3-dominated sour waters typically found in refinery services such as the overhead systems of some sour water stripper units. Phase II extended the initial research work in Phase I of the program, commonly referred to as the Sour Water JIP, which addressed NH4HS corrosion in H2S-dominated sour waters. This Phase II work in NH3-dominated sour waters studied the impact of several process variables including NH4HS concentration, NH3 partial pressure, H2S partial pressure, temperature, cyanide concentration, and velocity (wall shear stress). Data collected from laboratory tests designed to characterize these process variables were used to develop an enhanced software tool to predict corrosion rates for six materials evaluated in the program. Key aspects of the data, parametric behavior, and corrosion response of the different materials evaluated in the Phase II work are highlighted in this paper.
Keywords: sour water, ammonium bisulfide, NH4HS, hydrogen sulfide, H2S, ammonia, NH3, partial pressure, isocorrosion diagram, temperature, cyanide, velocity, wall shear stress, materials selection, software, sour water stripper.