Paul O. Ameh

A review on the assessment of polymeric materials used as corrosion inhibitor of metals and alloys

Corrosion control of metals is an important activity of technical, economical, environmental, and aesthetical importance. The use of inhibitors is one of the best options of protecting metals and alloys against corrosion. The toxicity of organic and inorganic corrosion inhibitors to the environment has prompted the search for safer corrosion inhibitors such as green corrosion inhibitors as other more environmental friendly corrosion inhibitors, most of which are biodegradable and do not contain heavy metals or other toxic compounds. Investigations of corrosion-inhibiting abilities of polymeric substances, e.g., plant gums, in addition to being environmentally friendly and ecologically acceptable, have shown that plant products are inexpensive, readily available, and renewable sources of materials. Need for more effective inhibitors has propelled companies such as the Montazhkhimzashchita Trust to develop a pool method of welding sheet vinyl, a method widely employed in gluing on roller sticky bands from thermoplast on a pipe. The article enumerates several kinds of polymeric materials which are suitable for use in combating corrosion, and several which have suitable strength characteristics as to serve in place of scarce expensive metals and alloys.

Commiphora pedunculata gum as a green inhibitor for the corrosion of aluminium alloy in 0.1 M HCl

The effect of Commiphora pedunculata (CP) gum on the inhibition of the corrosion of aluminum alloy AA 3001) in solutions of HCl was investigated using gravimetric and thermometric methods of monitoring corrosion. The results obtained indicated that CP gum is a good adsorption inhibitor for the corrosion of aluminum in solutions of HCl. The inhibition efficiency of CP gum was found to increase with an increase in concentration but to decrease with increasing temperature. The adsorption of CP gum on the surface of aluminum was found to be endothermic, spontaneous and to support the mechanism of physical adsorption. The Langmuir adsorption model has been used to describe the adsorption characteristics of CP gum on aluminum surface.

ADSORPTION AND QUANTUM CHEMICAL STUDIES ON THE INHIBITION OF THE CORROSION OF ALUMINUM IN HCL BY GLORIOSA SUPERBA (GS) GUM

Physico-chemical constituents of Gloriosa superba gum exudate were analyzed using recommended chemical methods. Results obtained from FT-IR study indicated the presence of functional groups that are typical for polysaccharides. Gas chromatography-mass spectrometry spectrum of the gum revealed the presence of 1-piperoylp, 1-penta-decarboxylic acid, 9-octadecenoic acid, and stigmasta-5,22-dien-3-ol. Based on its chemical constituents, corrosion inhibition potentials of various concentrations of the gum were investigated using FT-IR and gravimetric methods. The results obtained showed that Gloriosa superba gum is an inhibitor for the corrosion of Al in solution of HCl. The initial mechanism for the inhibition of Al corrosion by Gloriosa superba gum was found to be physiosorption and was succeeded by chemisorption. Although the Langmuir adsorption model supported the adsorption characteristics of the gum, the existence of interaction between the inhibitor particles was confirmed by the fitness of Flory-Huggins, Parsons, and Volmer adsorption isotherms. Analysis of El-Awady et al. kinetic isotherm revealed the formation of multiple layers of inhibitor on the surface of Al. The adsorption strength of the inhibitor was also found to increase with increasing temperature. Data obtained from the application of the Gibb-Helmholtz equation and Bockris-Swinkle adsorption model reflected spontaneous adsorption of the gum on the Al surface through chemisorption. From quantum chemical studies, it was found that the adsorption of the gum on the Al surface is facilitated by the presence of amide and hydroxyl functional groups in stigmasta-5,22-dien-3-ol and 1-piperoylp respectively.

Rheological Modeling and Characterization of Ficus platyphylla Gum Exudates

Ficus platyphylla gum exudates (FP gum) have been analyzed for their physicochemical parameters and found to be ionic, mildly acidic, odourless, and yellowish brown in colour. The gum is soluble in water, sparingly soluble in ethanol, and insoluble in acetone and chloroform. The nitrogen (0.39%) and protein (2.44%) contents of the gum are relatively low. The concentrations of the cations were found to increase according to the following trend, Mn>Fe>Zn>Pb>Cu>Mg>Cd>Ca. Analysis of the FTIR spectrum of the gum revealed vibrations similar to those found in polysaccharides while the scanning electron micrograph indicated that the gum has irregular molecular shapes, arranged randomly. The intrinsic viscosity of FP gum estimated by extrapolating to zero concentrations in Huggins, Kraemer, Schulz-Blaschke, and Martin plots has an average value of 7 dL/g. From the plots of viscosity versus shear rate/speed of rotation and also that of shear stress versus shear rate, FP gum can be classified as a non-Newtonian gum with characteristics-plastic properties. Development of the Master_s curve for FP gum also indicated that the gum prefers to remain in a dilute domain (ClC∗), such that 𝜂sp𝛼C1.2. The apparent activation energy of flow for FP gum (calculated from Arrhenius-Frenkel-Eyring plot) was relatively low and indicated the presence of fewer inter- and intramolecular interactions.

Thermodynamic, Chemical and Electrochemical Investigations of 4-Hydrobenzoic Acid as Corrosion Inhibitor for Mild Steel Corrosion in Hydrochloric Acid Solutions

The corrosion inhibition of mild steel in 0.1M HCl solution by 4-hydrobenzoic acid was studied at temperature range 303, 313, 323 and 333 K using weight loss measurement, thermometric, Polarization Resistance, Potentiodynamic Polarization, Electrochemical Impedance Spectroscopy, Scanning Electron Microscopy (SEM) and Fourier transformed infra-red spectroscopy (FTIR) techniques. The results obtained at 303 K indicated that the studied inhibitor had established >88% inhibition efficiency at an optimum concentration of 0.10 M. The adsorption of 4-hydrobenzoic acid takes place according to Langmuir`s adsorption isotherm. Kinetic parameters (activation energy, Ea and pre-exponential factor, A) as well as thermodynamic parameters (enthalpy, entropy and free energy of adsorption; ΔHads o ΔSads o, and ΔGads o respectively) were calculated and discussed. Potentiodynamic polarization studies indicate that 4-hydrobenzoic acid acts as a mixed type of inhibitor. Data collected from EIS studies has been analyzed to model the appropriate equivalent circuit for better explanation of corrosion inhibition process. The surface analysis study using SEM confirms the corrosion of the mild steel and its inhibition by the inhibitor. FTIR spectra of the inhibitor and the corrosion product of mild steel (in the presence of the inhibitor) reveal that there were shifts in frequencies of adsorption suggesting that some functional groups were used in adsorption and some new bonds were formed.