Ammonium salts represent a common problem for the refining industry. These saltslead to fouling of piping and heat exchangers resulting in loss of duty, underdeposit corrosionwhen wetted, and corrosive sour water solutionsonce sufficient water is available to dissociate these salts into solution. To properly manage fouling and corrosion associated with these salts, knowledge of the temperatures at which these salts will deposit is critical. In this age of process control, these temperatures can be predicted in real-time provided the salt deposition temperature relationships are known. The salt deposition equations for salts most often encountered in refining are not in the public domain. To close this gap, ammonium salt deposition equations were derived for NH4Cl, NH4HS, NH4Br, and NH4Fusing fundamental thermodynamic equations of state with published thermodynamic properties for the individual chemical species/reactions.