The results of electrochemical techniques indicated that there were the decrease of current density and the appearance of protective film on the steel surface evidencing the presence of inhibitor and the effect of Pr(4OHCin)3 compound depending on its concentration in solution. | Vietnam Journal of Science and Technology 55 (5B) (2017) 94-102 A STUDY ON PRASEODYMIUM 4-HYDROXYCINNAMATE AS AN INHIBITOR FOR CARBON STEEL IN FRESH COOLING WATER SYSTEM OF CA MAU FERTILIZER PLANT D. T. Ngan1, L. T. Dai1, 2, P. M. Q. Binh1, *, M. Vaka3, N. D. Nam1, * 1 Petrovietnam University, 762 Cach Mang Thang Tam Street, Ba Ria City, Ba Ria - Vung Tau Province, Vietnam 2 Department of Naval Architecture and Ocean Engineering, Pusan National University, Busan 609-735, Republic of Korea 3 School of Life and Environmental Sciences, Deakin University, Victoria 3220, Australia * Email: binhpmq@ and namnd@ Received: 1 August 2017; Accepted for publication: 8 October 2017 ABSTRACT Praseodymium 4-hydroxycinnamate compound has been successfully studied as an effective corrosion inhibitor for carbon steel in M NaCl solution using electrochemical techniques and surface analysis. The results of electrochemical techniques indicated that there were the decrease of current density and the appearance of protective film on the steel surface evidencing the presence of inhibitor and the effect of Pr(4OHCin)3 compound depending on its concentration in solution. The surface analysis show a confirmation of the protective film formation which is a result of adsorption between the metal and inhibitor components. In addition, inhibition performance of Pr(4OHCin)3 compound is also compared to the inhibition performance of TRACT 109, which has been added to a fresh cooling water system of Ca Mau fertilizer plant. Keywords: Ca Mau fertilizer plant; fresh cooling water system; carbon steel; corrosion inhibitor; Praseodymium 4-hydroxycinnamate 1. INTRODUCTION Carbon steel structures can be easily corroded in many applications, such as pipelines and/or tanks under various conditions with neutral pH in the air or low pH in a CO2 atmosphere or evenly in seawater [1 - 4] containing large amounts of chloride ions which is the cause of the growth of the pit by .