Abstract
The effects of the addition of poly(4‐vinylpyridine) (P4VP) and its derivative poly(4‐vinylpyridine poly‐3‐oxide ethylene) (P4VPPOE) on the corrosion of Cu60‐Zn40 in 0.5M HNO3 have been investigated by potentiodynamic and weight loss measurements. Both of the studied polymers decrease the corrosion rate. Their inhibition efficiency (E%) increases with the concentration. The maximum of inhibition was obtained for P4VPPOE (100 per cent at 10–5M). E% obtained from cathodic Tafel plots and weight loss methods were in good agreement. The inhibitors were adsorbed on the Cu60‐Zn40 surface according to the Frumkin adsorption isotherm model. P4VPPOE acts as a cathodic inhibitor and its efficiency is temperature independent.
Details
Keywords
S.A. Umoren, O. Ogbobe, E.E. Ebenso and U.J. Ekpe
To investigate the effect of halide ions on the corrosion inhibition of mild steel using polyvinyl alcohol (PVA) in H2SO4 at 30‐60°C and to study the mechanism of action.
Abstract
Purpose
To investigate the effect of halide ions on the corrosion inhibition of mild steel using polyvinyl alcohol (PVA) in H2SO4 at 30‐60°C and to study the mechanism of action.
Design/methodology/approach
The corrosion rates were determined using the gravimetric (weight loss) and gasometric (hydrogen evolution) techniques. The results obtained in the absence and presence of PVA, halides, PVA – halides combination were used to calculate the inhibition efficiency (%I), degree of surface coverage and to propose the mechanism of inhibition and type of adsorption.
Findings
Results obtained showed that inhibition efficiency (%I) increased with the increase in concentration of PVA, on the addition of halides and with the increase in temperature. Phenomenon of chemical adsorption was proposed and PVA was found to obey Langmuir, Flory‐Huggins and Freundlich adsorption isotherms. The synergism parameter, S1, evaluated was found to be greater than unity and the values of Ea, ΔH°, ΔS° and ΔG° obtained revealed that the adsorption process was spontaneous.
Research limitations/implications
Electrochemical studies such as polarization and AC impedance spectra will enlighten more on the mechanistic aspects of the corrosion inhibition and more polymers need to be evaluated as corrosion inhibitors.
Practical implications
PVA can be used as corrosion inhibitor and the addition of halides to PVA improves the inhibition efficiency considerably.
Originality/value
This paper provides new information on the effects of halides on the corrosion inhibition using PVA as an inhibitor for mild steel in acidic medium. Such a study had not been reported elsewhere.