Synthesis and Characterization of Nicotinonitrile Derivatives as Efficient Corrosion Inhibitors for Acid Pickling of Brass Alloy in Nitric Acid

Abstract

Abstract Three nitrogen‐heterocyclic nicotinonitriles compounds 4, 6‐dimethyl‐2‐(methylamino)‐nicotinonitrile 3 ; 2‐(dimethylamino)‐4, 6‐dimethyl‐nicotinonitrile 4 , 2‐((3‐bromophenyl)‐amino)‐4, 6‐dimethyl‐nicotinonitrile 5 are prepared and characterized by Fourier transformer infra‐red spectroscopy, proton nuclear magnetic resonance, mass spectrometry and elemental analysis. Novelty of study is synthesis and evaluation of new series organic compounds of related chemical structures as corrosion inhibitors acid pickling of brass alloy by nitric acid. Compound 5 is prepared for the first time. Compounds 3 – 5 are potent biocides and efficient corrosion inhibitors for brass alloy. Inhibition efficiency 94 %, 95 %, 96 % are achieved at 180 ppm compounds 3 – 5 , respectively. Inhibition efficiency followed the order: compound 5 > 4 > 3 . For compound 5 , increase charge transfer resistance and decrease in capacitance of electrical double layer confirmed adsorption mechanism. Limiting current indicated that corrosion is controlled by mass transfer of oxygen toward metal surface. Inhibition efficiency followed quantitative structure activity relationships. For the same molecular chemical structure of nicotinonitriles compounds 3 – 5 , Substituents methylamino, dimethylamino and 3‐bromophenylamino increased inhibition efficiency following the order: 3‐Br‐C 6 H 4 NH>(CH 3 ) 2 N>CH 3 NH.