Corrosion Inhibition of Passivated AISI – 1020 Steel in 3.5 % NaCL Solution Using Organic Inhibitors

It is well know that recirculating open cooling water system at metal/ water surface contact appear frequent corrosion products, like scales, foaling and material losses which are have great effect on cooling process. Passivation helps to maintain clean heat transfer surface by inhibiting oxides scales through creating outer passive layer. After definite time breakdown due to mechanical or chemical actions will take place. Therefore, it is necessary to add other organic compounds to treat the places pf collapse of previous protective layer formed by reaction of passivator with carbon steel. Corrosion inhibitor is a chemical compound that, when added to corrosive medium decreases the corrosion rate of a material with medium. Corrosion inhibitors are common used in industry. Organic inhibitors Phosphonobutane-1,2,4-tricarboxylic acid (PBTC) – C7H11O9P and Amine -C35H38Cl2N8O4 will be used. The study of corrosion inhibition for passivated carbon steel pipe line in recirculation open cooling water system was the aim of this present work. Maximum efficiency of inhibitors was determined and surface morphology were investigated using optical, scanning microscopy, phase analysis of the formed protective layer was examed by XRD and EDX. Corrosion in running water with and without inhibitors at 2 m3/hr flow rate was investigated using corrosion coupon rack. In running flow test, the corrosion rate of passivated carbon steel decreases from about 18 mpy to about 3 mpy after adding 200 ppm PBTC and 2.5 mpy after adding 150 ppm amine respectively in 3.5% NaCL solution at 250C and 6.5-7.5 PH, while In potentiodynamic polarization technique (stagnant), the corrosion rate of passivated carbon steel decreases from 7 mpy to 1.2 mpy after adding 200 ppm PBTC and 1 mpy after adding 150 ppm amine respectively in 3.5% NaCL solution at 250C and 6.5-7.5 PH.