Corrosion by wet ammonium chloride salt is a significant concern in many refining process units.
Because corrosion rates typically experienced can be extremely high when all of the conducive
conditions are met, every attempt is made to prevent this corrosion from occurring. This includes
process design, corrosion resistant materials, and source control of chlorides. However, despite the
best effort by the industry, ammonium chloride continues to pose a serious threat to the integrity of
refining equipment and the process safety of refineries because the omnipresence of chlorides in a
refinery. This paper presents a recent effort to further minimize this threat. It includes advances in the
fundamental understanding of ammonium chloride salt behavior, predictive modeling effort based upon
such fundamentals, the integration of such models with process and operating conditions in real-time,
and guidance for inspection in search of this highly elusive corrosion phenomenon.
Keywords: ammonium chloride, dew point, dry point, corrosion prediction model, salt formation,
ionic equilibria, hydroprocessing, distillation overhead systems