Chris O. Akalezi

Corrosion Inhibiting Effect of Aframomum melegueta Extracts and Adsorption Characteristics of the Active Constituents on Mild Steel in Acidic Media

The extract from the seeds of Aframomum Melegueta (AM) was investigated as corrosion inhibitor for mild steel in aerated 1 M HCl and 0.5 M H2SO4 solutions using gravimetric and electrochemical techniques. AM extract was found to inhibit both the cathodic and anodic partial reactions of the corrosion process, via adsorption of the organic matter on the metal/solution interface, as described by the Langmuir as well as Flory-Huggins adsorption isotherms. Corrosion rates in all systems studied increased with rise in temperature. Increasing the temperature of the system enhanced inhibition efficiency of AM extract in 1 M HCl, but decreased efficiency in 0.5 M H2SO4. Molecular dynamics simulations were performed to theoretically illustrate the electronic structure and adsorption behaviour of the active constituents of the seeds of Aframomum melegueta; paradol (1-(4-Hydroxy-3-methoxyphenyl)decan-3-one) and shogaol ((E)-1-(4-Hydroxy-3- methoxyphenyl)dec-4-en-3-one) in order to theoretically evaluate their contributions to the corrosion inhibiting action of the extract.

Application of aqueous extracts of coffee senna for control of mild steel corrosion in acidic environments

BackgroundThe inhibitive effect of the aqueous extract of Coffee senna (CS) on the corrosion of mild steel in 1 M HCl and 0.5 M H2SO4 solutions was investigated by weight loss measurement as well as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements.ResultThe extract was found to efficiently inhibit the corrosion process in both environments and inhibition efficiency increased with extract concentration as well as rise in temperature. Data from electrochemical measurements suggest that the extract functioned by adsorption of the organic matter on the metal/corrodent interface, inhibiting both the anodic and cathodic half reactions of the corrosion process. Adsorption of the extract organic matter was approximated by the Langmuir isotherm. The adsorption behavior of selected organic constituents of the extract on the metal surface was assessed at the molecular level, in the framework of the density functional theory.ConclusionThis study clearly shows the potentials of CS extract for control of mild steel corrosion in acidic environment.

CORROSION INHIBITION AND ADSORPTION BEHAVIOR OF MALACHITE GREEN DYE ON ALUMINUM CORROSION

Malachite green dye (MG) was studied as a corrosion inhibitor for aluminum in 1.0 mol dm−3 HCl and 0.5 mol dm−3 KOH using the gravimetric technique. The results revealed an inhibiting effect of MG, which was highly restrained in 0.5 M KOH and pronounced in 1.0 M HCl. MG inhibited the corrosion reaction in the acidic medium by adsorption on the metal/solution interface following the Flory-Huggins isotherm. Inhibition efficiency increased with MG concentration and synergistically increased in the presence of iodide ions, but decreased with a rise in temperature. The local reactivity of the MG molecule was analyzed theoretically using the density functional theory to explain the adsorption characteristics, while molecular dynamics simulations were performed to illustrate the adsorption structure of MG at a molecular level. The theoretical predictions showed good agreement with experimental results.

Inhibitive effect of methyl green dye on the corrosion of low carbon steel in acidic media

Purpose – The purpose of this paper is to study methyl green dye (MG) as a corrosion inhibitor for low carbon steel (LCS) in hydrochloric acid (1 M) and sulphuric acid (0.5 M) and to assess the effect of temperature variation and halide additives on the inhibition efficiency.Design/methodology/approach – Corrosion rates are monitored using the gravimetric technique. Inhibition efficiency is determined by comparing the corrosion rates in the absence and presence of additives. Attempts are also made to elucidate the inhibition mechanism from the trend of inhibition efficiency with change in temperature and type of acid anion.Findings – MG reduces the corrosion rate of the LCS specimens in both acid media within the investigated temperature range by adsorption at the metal/solution interface. Inhibition efficiency increases with MG concentration but decreases with rise in temperature. Maximum values of 67 and 73 per cent are obtained in 1 M HCl and 0.5 M H2SO4, respectively, at [MG]=0.001 mol dm−3. Halide ad...