A COMPARATIVE ELECTROCHEMICAL STUDY ON CORROSION INHIBITION OF IRON BY SYNTHESISED METHYL TRIPHENYLPHOSPHONIUM IODIDE IN ACID MEDIA

Abstract

The present work is aimed mainly to synthesize a phosphonuim salt, tetraphenylphosphonuim iodide, and evaluate inhibitive effect against carbon steel corrosion in aerated 1 M HCl solutions. Thus, tetraphenylphosphonuim iodide was synthesized by the reaction of of an equimolar quantity of a solution of phenyl iodide and triphenyl phosphine in toluene (84% yield). We have found that, the use of toluene for this reaction of triphenyl phosphine with aryl or alkyl iodide is a convenient synthesis of many phosphonium salts since the halogen as a leaving group (requires a temperature higher than boiling point of chloroform.The purity of this compound was estimated by TLC technique and microanalysis, while its structure was supported by the usual spectroscopic methods such as UV, infrared, 1 H. NMR and 13 C. NMR. Exploration of the Corrosion measurements based on polarization resistance (Rp), potentiodynamic polarization curves indicates that tetraphenylphosphonuim iodide, in most cases act as strong inhibitors. Tetraphenylphosphonuim iodide acts as anodic type inhibitors with predominant effect on the anodic dissolution of iron. Analysis of the polarization curves indicates that charge transfer process mainly controls carbon steel corrosion in HCl solution without and with phosphonuim salt. The mechanism of corrosion inhibition by phosphonuim; salt was discussed in the light of the molecular structure of the additive. A Comparative electrochemical study with that reported in the literature revealed that the efficiency of the inhibitors follows the order: tetraphenyl phosphonum iodide >(chloromethyl) triphenyl phosphonium chloride (CTP) > tetraphenyl phosphonum chloride (TP) > triphenyl phosphine oxide (TPO) > triphenyl (phenylmethyl) phosphonium chloride (TPM).