Indian pressurised heavy water reactors use Incoloy 800 for steam generators. The pH is maintained alkaline to check corrosion in secondary circuit by the addition of Ethanolamine (ETA). Effect of octadecylamine (ODA) for further reduction of corrosion is investigated. Incoloy was exposed to both steam and liquid phases at 200°C in an autoclave for 7 days. Concentration of ETA was kept constant at 6 ppm and that of ODA was varied from 6 ppm to 20 ppm. The film grown in liquid phase was thinner and enriched with Cr, while the film grown in steam phase had larger particles and mixed-ferrite in nature. Electrochemical Impedance spectroscopy studies suggested the presence of a barrier film under both liquid and steam phase oxidation. The addition of ODA was comparatively more beneficial in liquid phase. The study showed that ODA is a promising amine to inhibit the corrosion of Incoloy 800 in secondary water chemistry conditions.