Investigation of cooling water inhibitors

11 INVESTIGATION OF COOLING WATER INHIBITORS ( M.Sc. Thesis ) Ayşe Tosun GAZ! UNIVERSITY INSTITUTE OF SCIENCE AND TECHNOLOGY 1995 ABSTRACT In this study, the inhibitor effect of chromate, molybdate, nitrite, borax, ortophosphate, benzoate, ascorbic acid and mixtures of these substances on the corrosion of carbon steel having % 0.18 C, % 0.04 S, % 0.03 Si, % 0.50 Mn, % 0.15 Ni and % 0.05 Mo was investigated. For this purpose, experiments were coducted in neutral media having 100 ppm Cr at room temperature. The inhibitor effect of some one component, binary and ternary inhibitor blends was investigated depending on the temperature and pH. The current-potential curves were obtained by potentiostatic (1 mV/s) method and the corrosion rates were determined extrapolation of the Tafel slope of the cahodic polarization curves method and linear polarization method. By the use of the determined corrosion rates percent inhibition values were calculated and these values were used in comparing the effectiveness of the substances as inhibitor. In conclusion, for the one component inhibitor studies, the inhibitor effects were found to be % 93 for solution containing 1 0 ppm chromate, % 95 for 50 ppm nitrite and % 90 for solution with 50 ppm molybdate. At the binary inhibitor studies, it was found that the inhibitor effects were % 95 for solution with 8 ppm nitrite+2 ppm ascorbic acid, % 97 with 1 ppm chromate+9 ppm molybdate. From the studies with the solutions containing three of these substances, it was observed that some such mixtures can be a good alternative to some one component and binary inhibitor mixtures.