The corrosion in crude unit overhead systems, specifically related to acidic attack and under-deposit corrosion caused by salt formation, has been extensively documented in both industry and literature. However, the absence of comprehensive corrosion data correlating critical environmental and flow variables has posed challenges in evaluating corrosion and selecting appropriate materials. To address this issue, a Joint Industry Program (JIP) was conducted with the primary objective of generating engineering data on the corrosion behavior of commonly used construction materials in atmospheric overhead systems of refinery crude distillation units (CDU-OH). The study focused on investigating the effects of HCl, NH3, NH4Cl, H2O, and H2S in the presence of ammonium chloride, aiming to identify key parameters associated with three prevalent forms of corrosion: under-deposit, water dew point, and aqueous corrosion. Through meticulous thermodynamic modeling and corrosion evaluations performed in simulated environments that accurately represented relevant conditions, the impact of these key parameters on the corrosion of six frequently used materials of construction—namely, carbon steel, 410 stainless steel, Alloy 400, Titanium, Alloy 625, and Alloy C-276—was rigorously evaluated. The corrosion rates of these materials under various test conditions were quantified, leading to the development of a corrosion prediction model. This model serves as a valuable tool for determining conditions for ammonium chloride-induced corrosion in CDU-OH systems, aiding in the assessment and decision-making processes pertaining to material selection.