Synergistic Effect of KI on Corrosion Inhibition of Mild Steel by Polynuclear Schiff Base in Sulphuric Acid

K S Shaju,Aby Paul,Vinod P Raphael,K Joby Thomas

doi:10.5402/2012/425878

Abstract

Synergistic effect of KI on the corrosion inhibition efficiency of polynuclear Schiff base, anthracene-9(10H)-one-3-aminopropanoic acid (A9O3AP), on mild steel (MS) in 0.5 M sulphuric acid solution has been investigated using weight loss measurements, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization studies. The results show that inhibition efficiencies on MS increase with increase in concentration of the inhibitor and enhancement in inhibition efficiency was observed on addition of potassium iodide due to synergism. The adsorptions, of inhibitor and inhibitor + KI on the surfaces of the corroding metal obey Freundlich and Langmuir isotherms, respectively. Polarization studies revealed that A9O3AP acts as a mixed type inhibitor. Thermodynamic parameters (; ) were calculated using the adsorption isotherms. A probable synergismtic mechanism is proposed.

Highlights

The use of certain organic compounds as inhibitors is the most practical method to prevent corrosion of the mild steel (MS) in acidic media [1, 2]
Weight loss of MS specimens in 0.5 M H2SO4 at 30◦C was determined at 24 h in the presence of various concentrations of inhibitor (A9O3AP) and inhibitor + KI
The corrosion rates, inhibition efficiencies, and surface coverage (θ) in the presence of inhibitor and inhibitor + 0.2 mM KI for MS specimens for the period of 24 h are shown in the Table 1

Summary

Introduction

The use of certain organic compounds as inhibitors is the most practical method to prevent corrosion of the mild steel (MS) in acidic media [1, 2]. Schiff bases are organic molecules possessing azomethine linkage and many of them act as effective potential corrosion inhibitors [4,5,6,7]. The addition of halide ions to sulphuric acid solutions containing organic inhibitors has been found to stabilize the adsorption of organic cations, leading to improved inhibition efficiency. The present investigation was undertaken to examine the corrosion inhibition behavior and synergism mechanism [12, 13] with I− of a novel polynuclear Schiff base (A9O3AP) derived from anthracene-9 (10H)-one and 3aminopropanoic acid in 0.5 M H2SO4 solution on MS at 303 K

Experimental

Results and Discussion

Mechanism and Explanation for Synergism

Conclusions