International Journal of Scientific and Research Publications, Volume 4, Issue 1, January 2014 1 ISSN 2250-3153 www.ijsrp.org Diphenyl Sulphide as Corrosion Inhibitor for Zinc Metal in Acid Solutions A.Pasupathy 1* , S.Nirmala 1 , P.Sakthivel 2 , G.Abirami 1 and M.Raja 1 1 P.G and Research Department of Chemistry, Urumu Dhanalakshmi College, Tiruchirappalli, Tamil Nadu, India. 2 P.G and Research Department of Physics, Urumu Dhanalakshmi College, Tiruchirappalli,, Tamil Nadu, India. Abstract- This work deals with the evaluation of diphenyl sulphide as a corrosion inhibitor for zinc in 0.5N HCl and 0.5N H 2 SO 4 by conventional weight loss and gasometric methods. Results indicate that diphenyl sulphide exhibited high inhibition efficiencies in both the acids but performed better in 0.5N H 2 SO 4 than in 0.5N HCl. The inhibition efficiency was found to increase with increase in the inhibitor concentration. The adsorption of the inhibitor molecules on the zinc metal surface obeyed Temkin adsorption isotherm. Index Terms- Diphenyl sulphide, acidic solutions, zinc corrosion, weight loss, gasometry. I. INTRODUCTION cid pickling, acid cleaning and acid descaling are some of the industrial process in which metals are exposed to different acids of various concentrations. In order to reduce the metal loss and acid consumption corrosion inhibitors are added to the acid solutions 1-8 . Organic compounds containing nitrogen, oxygen and sulphur in their molecular structures have been reported to function as effective inhibitors for various metals in different corrosive media. The efficiency of these compounds as corrosion inhibitors is attributed to the number of mobile electron pairs present 9 , the π-orbital character of the electrons 10 and the electron density around the hetero atoms 11 . The efficiency of the corrosion inhibitors are also reported to be influenced by their molecular structure, molecular size and the nature of the substituent groups 12, 13 . These compounds minimize the corrosion rate of the metals by getting adsorbed on the metal surface thereby blocking the active sites on the metals. In the present work, we have evaluated diphenyl sulphide as an inhibitor for zinc corrosion in 0.5N HCl and 0.5N H 2 SO 4 using the conventional weight loss and gasometry methods. The efficiency of the inhibitor was evaluated at four different concentrations. II. EXPERIMENTAL The zinc metal specimens of composition: lead 1.03%, cadmium 0.04%, iron 0.001% and the remainder being zinc and size of 4cm*2cm* 0.08cm with a small hole of approximately 3mm near the end of the specimen were used for weight loss and gasometry studies. Zinc metal specimens were polished with a series of emery papers of various grades from 400-1200, degreased with absolute ethanol and air dried. The inhibitor compound, diphenyl sulphide was imported from the Fluka AG of Switzerland. The corrosion medium was 0.5N HCl and 0.5N H 2 SO 4 prepared from A.R grade HCl and H 2 SO 4 and deionised water. III. WEIGHT LOSS AND GASOMETRY STUDIES Weight loss and gasometry studies were conducted as reported earlier 14,15 .From the weight loss experiments the % inhibition efficiency (I.E) and the degree of surface coverage (θ) were calculated by using the following equations. Where W o and W i are the weight loss of the metal in the absence and presence of the inhibitor respectively. The corrosion rate (C.R) of the metal was calculated by using the following equation. Where W is the weight loss of the zinc metal (mg), A is the surface area of the metal specimen(cm 2 ), t is the exposure time (h) and D is the density of the metal (g/cm 3 ). From the gasometry experiments the inhibition efficiency is calculated by using the following equation. Where V o and V i are the volume of hydrogen gas evolved in the absence and presence of the inhibitor respectively. IV. RESULTS AND DISCUSSION Values of inhibition efficiency obtained from the weight loss and gasometry experiments for the inhibitor for the corrosion of zinc in 0.5N HCl and 0.5N H 2 SO 4 in the presence of different concentrations of dipheny sulphide are presented in the tables 1and 2 respectively. A