www.iaset.us editor@iaset.us INVESTIGATION ON N-FORMYL PIPERIDIN-4-ONES AS CORROSION INHIBITORS FOR CARBON STEEL IN ACID MEDIUM A. ILAMPARITHI 1 , S. PONNUSWAMY 2 & A. SELVARAJ 3 1,2 PG and Research Department of Chemistry, Government Arts College (Autonomous), Coimbatore, Tamil Nadu, India 1 Department of Chemistry, Gobi Arts and Science College, Gobichettipalayam, Tamil Nadu, India 3 PG and Research Department of Chemistry, CBM College, Coimbatore, Tamil Nadu, India ABSTRACT The corrosion inhibition of mild steel in 1N H 2 SO 4 and 1N HCl in the presence of N-formyl piperidin-4-ones was studied using gravimetric and electrochemical techniques. Results obtained show that these compounds are excellent inhibitors and inhibit better in HCl than in H 2 SO 4 . The potentiodynamic polarisation studies clearly reveal that they are mixed type inhibitors. The impedance parameters (R ct and C dl ) clearly indicate the adsorption of N-formyl piperidin-4-ones on the metal surface leading to the formation of a protective layer which grows with increasing exposure time. The adsorption of N-formyl derivatives on mild steel surface in both the acid media follows a Langmuir adsorption isotherm and Tempkin adsorption isotherm. The mild steel-FP complex layer formed at the metal surface was identified by infrared spectral analysis and SEM/EDS. KEYWORDS: 1. Corrosion Inhibitors, 2. Mild Steel, 3. Electrochemical Impedance Spectroscopy, 4. Polarisation Curves, 5. Adsorption Isotherm, 6. N-Formyl Piperidin-4-One, 7. FT-IR , 8. SEM/EDS INTRODUCTION Generally HCl and H 2 SO 4 are employed in the treatment of steel and ferrous alloys in industry. The use of inhibitors containing heteroatom’s like nitrogen, oxygen, and sulphur is one of the most practical methods for protection against corrosion in acid media [1] . The aim of this study is to investigate the inhibitive properties of some azacyclic inhibitors viz. N-formyl-t-3-methyl-r-2,c-6-diphenylpiperidin-4-one (F3MPO), N-formyl-t-3-isopropyl-r-2, c-6-diphenylpiperidin-4-one (F3IPPO), N-formyl c-3,t-3-dimethyl-r-2,c-6-diphenylpiperidin-4-one (F3DMPO) and N-formyl t-3,c-5-dimethyl-r-2,c-6-diphenylpiperidin-4-one (FDMPO) on the corrosion of mild steel in sulphuric acid and hydrochloric acid. The chemical structures of the inhibitors are given in Figure 1. (A) (B) International Journal of Applied and Natural Sciences (IJANS) ISSN(P): 2319-4014; ISSN(E): 2319-4022 Vol. 3, Issue 2, Mar 2014, 63-80 © IASET