Abstract This paper reports the insight into corrosion product layer (CPL) evolution on C-steels in presence of inhibitor as a function of varying multiphase flow parameters. Mutiphase flow conditions are simulated as they exist in oil and gas lines. The main objective of this paper is to understand the effects of multiphase flow (full pipe vs. slug flow) on the morphology of the C- steel coupon subjected to a horizontal test loop. The corrosion product layer formed on the surface of the steel coupons and the cross-sectional view were analyzed using Scanning Electron Microscopy (SEM) and Focussed Ion Beam (FIB) techniques. Near Edge X-ray Absorption Fine Structure Spectroscopy (NEXAFS) was used to understand the imidazoline absorption kinetics and its molecular orientation on C-steel substrate.