Adsorption and Corrosion Inhibition Characteristics of Some Nicotinamide Derivatives on Mild Steel in Hydrochloric Acid Solution

M P Chakravarthy,K N Mohana

doi:10.1155/2014/687276

Abstract

The present investigation includes the study of corrosion inhibition effect of N-(1H-Indol-3-ylmethylene)-nicotinamide (IMN) and N-(3,4,5-trimethoxy-benzylidene)-nicotinamide (TMN) on mild steel in 0.5 M HCl by mass loss and electrochemical measurements. The obtained results showed that inhibition efficiency increased with the increasing concentration of inhibitors and decreased with increase in temperature and immersion time. Potentiodynamic polarization curves indicate that both IMN and TMN were acting as mixed type of inhibitors. Langmuir adsorption isotherm model was employed to determine the equilibrium of adsorption for inhibiting process in both inhibitors. Nyquist plots revealed that, as the concentration of the inhibitors increases, double layer capacitance (Cdl) and corrosion current (icorr) decreases, while polarization resistance (Rp) increases. Various thermodynamic parameters for the adsorption of inhibitors on mild steel were computed and discussed. The passive film formed on the metal surface was characterized by FTIR, EDX, and SEM.

Highlights

Mild steel (MS) is cheap, strong, stiff, and widely used engineering material because of its good mechanical properties
Selection of an appropriate inhibitor ranging from rare earth elements [4] to organic compounds [5,6,7,8] for specific environment and metal is of great importance
The efficiency of these compounds is attributed to their steric factors, functional groups, lone pairs of electrons present on the hetero atoms, and pi-orbital character of donating electrons which determine the type of interaction between organic molecules and the metallic surfaces

Summary

Introduction

Mild steel (MS) is cheap, strong, stiff, and widely used engineering material because of its good mechanical properties It is the most important structural material exposed to outdoor conditions especially in acidic media [1] where corrosion is considerably more severe. A large number of organic compounds, those containing nitrogen, oxygen, or sulphur in a conjugated system, are known to be applied as inhibitors to control acid corrosion of iron and steel. A large number of organic compounds containing nitrogen, oxygen, or sulphur have been used as inhibitors to control acid corrosion of iron and steel [11, 12]. The adsorption characteristics of organic molecules are affected by sizes, electron density at the donor atoms, and orbital character of donating electrons [13,14,15,16]. The inhibition performances of the two derivatives have been compared and discussed

Experimental Procedure

Methods

Results and Discussion

Conclusions