Hydrogen Evolution Techniques Research Articles

Bimodal Trending in Corrosion Loss of Magnesium Alloys

Data for the mass loss of a variety of magnesium alloys as a function of an exposure period show that corrosion loss follows bimodal trending with time for different exposure environments, with both laboratory and field supporting these findings. For datasets sufficient to discriminate bimodal behavior, the instantaneous rate of corrosion at the commencement of the second mode is (close to) four times the instantaneous rate of corrosion at the end of the first mode (i.e., through the transition period). This observation is consistent with the theoretical relative diffusivities of oxygen and hydrogen through the corrosion product layer as it exists during the transition period. These findings support the notion that the bimodal model has corrosion in mode 1 rate-controlled by the cathodic oxygen reduction reaction and the inward diffusion of oxygen while in mode 2 corrosion is rate-controlled by the cathodic hydrogen evolution reaction and the outward diffusion of hydrogen. Similar findings have been made previously for various ferrous and other alloys and thus throws new light on the development of corrosion of magnesium alloys. It also provides reasons for measurements of hydrogen evolution and electrochemical techniques underestimating magnesium corrosion rates. A new procedure for combining these is proposed.

PERFORMANCE OF METHANOL EXTRACT OF Kalanchoe crenata LEAVES ON CORROSION OF MILD STEEL IN 5.0 M ACID MEDIUM.

The inhibitive performance of the methanol extract of an eco-friendly green inhibitor Kalanchoe crenata (KC) leaves on the corrosion of mild steel in 5.0 M H2SO4 solution with inhibitor concentrations of 1 g/L, 2 g/L, 3 g/L, 4 g/L and 5 g/L, at the temperatures of 333 K and 353 K was studied using gravimetric (weight loss) and gasometric (hydrogen evolution) techniques to determine its inhibition efficiencies as well as to depict the mechanism of inhibition of the inhibitor. The gravimetric technique was done for 5 Hours. Results indicate that the leaf extract inhibited the corrosion process efficiently. The extract showed inhibition efficiency of 84.95% and 84.24% (333 K) for gravimetric and gasometric analysis respectively. The Inhibition efficiency was found to increase with an increase in the extract concentration and also increased with an increase in time but decreased with increase in temperature. Thermodynamic considerations revealed that the activation energy, Ea increased in the presence of the plant extract. The kinetic data confirmed the reaction process to be first order. Adsorption of the plant extract on mild steel surface is an exothermic process and spontaneous as deduced by negative Qads mean value (-10.39 kJ/mol) and negative ∆Gads values (-11.54 and -10.49 kJ/mol). The mechanism of adsorption proposed for the plant extract on the mild steel surface is physical adsorption. Experimental data obtained fits the Langmuir adsorption isotherm.

Chemical, Electrochemical, and Surface Morphological Studies of the Corrosion Behavior of the AZ31 Alloy in Simulated Body Fluid: Effect of NaOH and H2O2 Surface Pretreatments on the Corrosion Resistance Property.

Magnesium and its alloys have attracted attention for biomedical implant materials in dental and orthopedic applications because of their biodegradability and similar properties to human bones. The very high rate of degradation in the physiological systems is, however, a major setback to their utilization. Chemical modification is one of the approaches adopted to enhance the corrosion resistance property of Mg and its alloys. In this work, NaOH and H2O2 were used as a pretreatment procedure to improve the corrosion resistance of the AZ31 Mg alloy in simulated body fluid (SBF). Advanced techniques such as dynamic electrochemical impedance spectroscopy (dynamic-EIS), atomic force microscopy, and optical profilometry were used in addition to the classical mass loss, hydrogen evolution, EIS, and polarization techniques to study the corrosion resistance property of the alloy in SBF for 30 h. Results obtained show that the surface treatment significantly enhanced the corrosion resistance property of the alloy. From dynamic-EIS at 30 h, the charge transfer resistance of the untreated AZ31 Mg alloy is 432.6 Ω cm2, whereas 822.7 and 2617.3 Ω cm2 are recorded for NaOH- and H2O2-treated surfaces, respectively. H2O2 is a better treatment reagent than NaOH. The mechanism of corrosion of both untreated and treated samples in the studied corrosive medium has been discussed.

Phytochemical Constituent and Anti-corrosion Properties of the Root Extract of Phyllanthus mellerianus (Nvo-nkwu) Plant on Mild Steel in 1.5M HCl Medium

The research reports on the phytochemical constituents and anti-corrosion properties of the root extract of Phyllanthus mellerianus on mild steel in 1.5M HCl. The powdered root was extracted with ethanol and concentrated with a rotary evaporator. The phytochemical constituents’ were achieved through GC-MS, FTIR and wet analysis. The anticorrosion properties were investigated via weight loss, hydrogen evolution techniques, and SEM analysis. The phytochemical investigation reveals the presence of tannins, flavonoids, phenols, and terpenoids at reasonable percentages. At different temperatures of 303K, 313K, and 323K, the inhibition efficiency, enthalpy, entropy, activation energy, Gibbs free energy, and adsorption isotherms were extrapolated with some models. The inhibition efficiency increased with an increase in the concentration of the extract, an indication of the inhibitive property of the root extract. This was supported through the extrapolation of Gibbs free energy, activation energy, enthalpy, and entropy change. The thermodynamic variable shows that the mechanism of inhibition was physisorption, whereas the kinetics study confirmed a first-order kinetic on the corrosion of mild steel in hydrochloric acid. The values of the linear regression R2 confirm the inhibitive impact of the root extract on mild steel in an acid medium. The presence of the heteroatoms N, O, and S in the root extracts of Phyllanthus mellerianus has been attributed to their inhibitory effectiveness.

PHYLLANTHUS MELLERIANUS STEM INHIBITION PROPERTIES FOR MILD STEEL CORROSION IN 1.0 M HCL MEDIUM: ADSORPTION, KINETICS AND THERMODYNAMIC INVESTIGATION

The deterioration of mild steel when exposed to acids, alkalis, and salt solutions is a problem in industrial processes. The corrosion of metals and their alloys has sparked a surge in research efforts to minimize the damage caused by the corrosion process. The research reports the corrosion inhibition properties of Phyllanthus mellerianus stem on mild steel in 1.0 M HCl solution using weight loss and hydrogen evolution techniques. The powdered sample was extracted with ethanol and concentrated with a rotary evaporator. The functional group of the extract, elemental analysis, and morphology of the mild steel were studied with FTIR and SEM. The FTIR analysis confirms the presence of functional groups with nitrogen, oxygen, sulphur, and aromatic rings, whereas the SEM reveals the elements and the morphological structure of the mild steel in the presence and absence of inhibitors in an acid corrodant. Some models were used to extrapolate the inhibition efficiency, enthalpy, enthropy, activation energy, Gibbs free energy, adsorption isotherms, and kinetics investigation. The inhibition efficiency increased with an increase in the concentration of the extract. The values of change in Gibbs free energy obtained at 303K, 313K, and 323K were negative, indicating that the stem extract of Phyllanthus mellerianus was strongly adsorbed on mild steel surfaces and stable at high temperatures. The change in Gibb’s free energy, enthalpy, and activation energy were less than and within the value of 21 kJ/mol. The extrapolation from the thermodynamic and kinetic models shows the effectiveness of the stem extract of PM and confirms the physical (physisorption) adsorption mechanism for the corrosion of mild steel surfaces. The R2 values obtained from the linear regression are strongly fitted to the Langmuir, Temkin, Freundlich, and El-Wadys thermodynic/kinetic isotherms. The inhibitory effectiveness of extracts has been attributed to the presence of the hetero atoms N, O, and S present in the stem extract of Phyllanthus mellerianus. KEYWORDS: Adsorption, Corrosion Inhibition, Kinetics, Mild Steel, Phyllanthus mellerianus stem, Thermodynamic Parameters

Experimental and quantum chemical studies of carboxylates as corrosion inhibitors for AM50 alloy in pH neutral NaCl solution

Sodium salts of mono- and di- carboxylic acids (glycolic, fumaric and benzoic acid) were studied as corrosion inhibitors for AM50 alloy in pH neutral aqueous NaCl environment. Hydrogen evolution, electrochemical and surface characterization techniques were employed to reveal their corrosion inhibition mechanism, whilst the molecular features of inhibitors were investigated by quantum chemical calculation. All inhibitors reduced anodic dissolution of AM50 and their efficiency generally increased with time and concentration from 5 mM to 100 mM. The inhibition mechanism can be described as physisorption of inhibitive molecules on the surface of the intrinsic oxide layer followed by chemisorption with Mg2+ and Al3+, and the difference in inhibition action among these inhibitors was explained on the molecular scale.

Experimental and theoretical evaluation of Aspirin as a green corrosion inhibitor for mild steel in acidic medium

A combined experimental and theoretical approach has been used to evaluate the corrosion inhibition potential of an ecofriendly, cost effective and benign compound (Aspirin) on mild steel in acidic media using hydrogen evolution technique within a temperature range 303 K–333 K in sulphuric acid solution. The results show that Aspirin inhibits the corrosion of mild steel in acidic media. The inhibition efficiency of Aspirin was found to increase with inhibitor concentration and decreased with rise in temperature. The maximum inhibition efficiency was 79.2 % with 800 mg/L of Aspirin at 333 K. The corrosion reaction kinetics in the presence of Aspirin shows a transition from first order to second order kinetics on going on elevating the temperature of the system. The trend in activation energy, Ea and the enthalpy of activation, ΔH indicate that the corrosion process is endothermic, the entropy of activation, ΔS shows that the process is spontaneous. The experimental results were in consonance with Langmuir isotherm and a physical adsorption mechanism is proposed for the adsorption of inhibitor on the mild steel surface. Complementary information was obtained from theoretical computations which show that the EHOMO and ELUMO for Aspirin are −7.33 eV and −2.06 eV, respectively. Molecular dynamics simulation reveals a strong binding affinity between inhibitor and the steel surface with a binding energy of −117.2 kcal/mol at the most stable adsorption configuration.

Thermodynamic and Adsorption Analysis of Corrosion Inhibition of Mild Steel in 0.5M HCl Medium <i>via</i> Ethanol Extracts of <i>Phyllanthus mellerianus</i>

The corrosion of mild steel is a problem in industrial processes based on its deterioration on exposure to acids, alkalis, and salt solutions. This issue has prompted an increase in research interest in order to mitigate the harmful effects of corrosion on metals and their alloys. The thermodynamic and adsorption analysis of mild steel in 0.5M hydrochloric acid solutions <i>via ethanol leaf extract of Phyllanthus mellerianus</i> was investigated using weight loss and hydrogen evolution techniques. The powdered sample was extracted with ethanol and concentrated with a rotary evaporator. The phytochemical analysis reveals the presence of tannins, flavonoids, phenols, and terpenoids at reasonable percentages. The inhibition efficiency, enthalpy, enthropy, activation energy, Gibbs free energy, and adsorption isotherms were extrapolated with some models. The inhibition efficiency increased with an increase in the concentration of the extract. The values of change in Gibbs free energy obtained at 303K, 313K, and 323K were negative, indicating that the leaf extract of <i>Phyllanthus mellerianus</i> was strongly adsorbed on mild steel surfaces and stable at high temperatures. The enthalpy of activation ranges from 43.08kJ/mol to 80.64kJ/mol. An increase in activation energy with inhibitor concentration confirmed the physical (physisorption) adsorption mechanism for the corrosion of mild steel surfaces. The R² values obtained from the linear regression are strongly fitted to the Langmuir and freundlich isotherms. The inhibitory effectiveness of extracts has been attributed to the presence of the hetero atoms N, O, and S present in their phytochemical composition.

Hydrogen production via water splitting over graphitic carbon nitride (g-C3N4 )-based photocatalysis

Abstract Photocatalytic splitting of water into hydrogen and oxygen using semiconductor photocatalysts and light irradiation has been attracted much attention and considered to be an alternative for nonrenewable fossil fuel to solve environmental problems and energy crisis and also an as promising approach to produce clean, renewable hydrogen fuel. Owing to their various advantages such as low cost and environmental friendly, chemical, and thermal stability, appropriate band structure, graphitic carbon nitride (g-C3N4 ) photocatalysts have gained multitudinous attention because of their great potential in solar fuels production and environmental remediation. However, due to its fast charge carrier’s recombination, low surface, and limited absorption of the visible light restrict their activity toward hydrogen evolution and numerous modification techniques were applied to solve these problems such as structural modification, metal/nonmetal doping, and noble metal loading, and coupling semiconductors. In this chapter, we summarize recent progress in the synthesis and characterization of the g-C3N4-based photocatalyst. Several modification methods used to enhance the photocatalytic hydrogen production of g-C3N4-based photocatalyst were also highlighted. This chapter ends with the future research and challenges of hydrogen production over g-C3N4-based photocatalyst.

Investigation of Corrosion Protection of Austenitic Stainless Steel in 5.5 M Polluted Phosphoric Acid Using 5-Azidomethyl-7-morpholinomethyl-8-hydroxyquinoline as an Ecofriendly Inhibitor

The use of 5-azidomethyl-7-morpholinomethyl-8-hydroxyquinoline (AMH) as a corrosion inhibitor for AISI 321 stainless steel in 5.5 M polluted phosphoric acid was investigated using the hydrogen evolution technique, linear polarization curves, and impedance spectroscopy. Impedance measurements revealed that the dissolution of AISI 321 in 5.5 M polluted phosphoric acid was controlled by an activation mechanism, unchanged even with the addition of AMH at different concentrations. Polarization results showed that the inhibition ability was enhanced with increasing inhibitor concentration. AMH acted as a mixed-type inhibitor by random adsorption on the alloy surface, whatever the nature of the reaction that is taking place. The adsorption of AMH on the AISI 321 surface was also discussed via the Langmuir adsorption isotherm. The influence of elevating the solution temperature on the corrosion inhibition performance was studied. A quantum chemistry study with the DFT method was also conducted, which supplied a logical and exploitable theoretical explanation of the adsorption and the inhibition action of AMH on AISI 321.

Achieving a high corrosion resistant and high strength magnesium alloy using multi directional forging

An attempt was made to develop a corrosion-resistant, high-strength Mg alloy using multi-directional forging (MDF). An extruded alloy as well as pure Mg was MDFed at temperatures between 220 and 340 °C with 40 °C intervals. Grains, second phase distribution, and Volta-potential difference between second phases and matrix were measured. Moreover, tensile and compression tests were used to assess mechanical properties. The corrosion behavior was characterized using electrochemical, hydrogen evolution, and mass loss techniques. A corrosion-resistant Mg alloy with a corrosion rate less than even high purity Mg obtained which has not been previously reported for a light Mg alloy. It was found that the lowest corrosion rate can be obtained for the alloy MDFed at 300 °C.

Corrosion behaviours of Ti6Al4V-Mg/Mg-Alloy composites

The effect of coupling of unalloyed Mg and Mg-alloys (AZ91 and WE43) with Ti6Al4V alloy on corrosion and degradation behaviours of produced composites has been investigated in simulated body fluid (SBF) by hydrogen evolution, and surface and electrochemical characterization techniques. Combining of unalloyed Mg with Ti6Al4V intensified galvanic corrosion and catastrophic failure occurred by initiation of microcracks formed by sudden hydrogen gas evolution. In contrast to other composites, Ti6Al4V-AZ91 composites, containing new TiAl3 interface layer formed during composite production, preserved their mechanical integrities due to lowest corrosion and degradation rate of AZ91 alloy.

Green corrosion protection for mild steel in acidic media: saponins and crude extracts of Gongronema latifolium

PurposeThis paper aims to appraise the inhibitory effect of saponins extracted from Gongronema latifolium (SEGL) on mild steel in acid media. This is in a bid to conserve our environment and maintain the integrity of engineering structures and materials.Design/methodology/approachThe corrosion inhibition of SEGL and ethanolic extracts of the leaves of G. latifolium (EEGL) on mild steel was studied by hydrogen evolution technique within a temperature range of 30-60°C in tetraoxosulphate (VI) acid solutions.FindingsThe extracts inhibit the corrosion of mild steel, and the inhibition efficiency depends on the concentration of the plant extract, temperature and the period of immersion. SEGL was comparatively more efficient than EEGL. Optimum values of the inhibition efficiency for both the EEGL and SEGL (93.7 and 96.5 per cent, respectively) were obtained at extract concentration of 10 g/L, whereas the least values were obtained at extract concentration of 0.5 g/L.Originality/valueThis paper provides new information on the possible application of isolated SEGL as an environmentally friendly corrosion inhibitor. The possible mechanism of the inhibitive action is also given.

Corrosion inhibition of pure Mg containing a high level of iron impurity in pH neutral NaCl solution

Three sodium salts of organic acids (2,5-pyridinedicarboxylic, 3-methylsalicylic and fumaric) were studied as corrosion inhibitors for pure magnesium containing a high level (342 ppm) of Fe impurity. The inhibition effect of the three inhibitors was evaluated by means of hydrogen evolution, electrochemical and surface analysis techniques. Significant reduction in corrosion rate was revealed for of the tested inhibitors in pH neutral NaCl electrolyte. 2,5-pyridinedicarboxylate and fumarate showed the effects characteristic for mixed-type inhibitors, while 3-methylsalicylate performed more as cathodic inhibitor, complying with the iron re-deposition model, where the electrochemical activity of iron-rich particles was effectively inhibited.

Corrosion behaviour of polypyrrole-coated WE43 Mg alloy in a modified simulated body fluid solution

The corrosion behaviour of PPy-coated WE43 Mg alloy in a simulated body fluid solution with daily electrolyte renewal is investigated by electrochemical, hydrogen evolution and analytical techniques. It is shown that the PPy coating effectively contributes to a decrease in the corrosion rate of WE43 Mg alloy and production of H2 gas. An increase in the PPy coating protective properties observed after every electrolyte renewal is attributed to: 1) a decrease in the coating conductivity by the adsorption of CO2 species, and 2) substrate/coating decoupling due to uncompensated coating positive charging and misalignment of the substrate and coating Fermi levels.

Thermodynamic and Kinetic Studies of Powerful Eco Friendly Green Inhibitors; Costus afer, Uvaria chamae and Xylopia aethiopia for the Control of Mild Steel Corrosion in HCl Solution.

The inhibitive action of the methanol extracts of three powerful eco-friendly green Inhibitors; Costus afer (COA), Uvaria chamae (UVC), and Xylopia aethiopica (XYA) leaves on the corrosion of mild steel in 2.5 M HCl solutions with inhibitor concentrations of 0.5 g/L, 1.0 g/L, 2.0 g/L and 4.0 g/L, at the temperatures of 30°C and 60°C was studied using gravimetric (weight loss) and gasometric (hydrogen evolution) techniques to determine their inhibition efficiencies as well as to characterize the mechanism of inhibition of these three green inhibitors. The gravimetric technique was done for 5 days (120 Hours). Results indicate that the leave extracts inhibit the corrosion process powerfully. COA, UVC and XYA extracts showed inhibition efficiency of (83.7, 84.6 and 87.0) and (85.0, 62.5 and 76.1) for gravimetric (weight loss) and gasometric analysis respectively. The Inhibition efficiency was found to increase with an increase in the extract concentration and decrease with an increase in time(days) and temperature. The inhibition efficiencies followed the trend XYA>UVC>COA and COA>XYA>UVC in gravimetric and gasometric analysis respectively. Thermodynamic considerations revealed that the activation energy, Ea increased in the presence of the plant extracts. The kinetic data confirmed the reaction process to be first order. Adsorption of the plant extracts on mild steel surface is an exothermic process and spontaneous as deduced by mostly negative Qads mean values of -7.40 KJ/mol, -2.14 KJ/mol and -32.18 KJ/mol for COA, UVC and XYA and negative ΔGads values of -9.28 KJ/mol and -12. 0 KJ/mol for COA, -9.46 KJ/mol and -11.23 KJ/mol for UVC and -7.73 KJ/mol and 6.29 KJ/mol for XYA at 30°C and 60°C respectively. The mechanism of adsorption proposed for the plant extract on the mild steel surface is physical adsorption. Experimental data obtained fit the Langmuir adsorption isotherm.

Solvent Free Glycolysis of Plastic Waste as Green Corrosion Inhibitor for Carbon Steel in Sulfuric Acid

Solvent free efficient green glycolysis of Polyethylene terephthalate waste, PET, in this respect, PET waste was subjected to depolymerization with propylene glycol in the presence of manganese acetate as a catalyst, the product is Bis-(3-hydroxy-propyl)-terephthalate, BHPT, as non-ionic surfactant was separated, characterized by FT-IR and 1HNMR, BHPT was evaluated as corrosion inhibitor for steel in the presence of 1.0 M sulfuric acid by chemical and electrochemical methods, the corrosion inhibition efficiency increase with inhibitor concentration and decrease with temperatures, the galvanostatic polarization curves indicate that the BHPT, compound act as mixed inhibitor, the impedance of the inhibited solution has increased with the increase in the concentration of the inhibitor. the inhibition due to adsorption of the inhibitor molecules on the steel surface, the adsorption obey Langmuir adsorption isotherm. Thermodynamic parameters were computed and discussed, Scanning electron microscope (SEM) was used to study the surface morphology of steel in absence and presence of the used inhibitor, hydrogen evolution techniques was used to evaluate the inhibition efficiency of the BHPT inhibitor compound. the data obtained from different techniques are in good agreement to each other and show the BHPT, surfactant derived from PET, waste considered as good corrosion inhibitor for steel in sulfuric acid.

Corrosion Inhibition of Aluminum–Silicon Alloy in Hydrochloric Acid Solutions Using Carbamidic Thioanhydride Derivatives

The corrosion inhibition of Al–Si alloy in 1 M HCl solution using some carbamidic thioanhydride derivatives at various concentrations has been studied using potentiodynamic polarization, electrochemical impedance spectroscopy, electrochemical frequency modulation, and hydrogen evolution techniques. Results obtained indicate that the inhibition efficiency (% η) reached 94 % at 2 × 10−5 M concentration and was found to increase with increasing the inhibitor concentrations. % η decreased with increasing the temperature. Potentiodynamic polarization curves showed that the investigated derivatives were mixed-type inhibitors. Some activation and adsorption thermodynamic parameters (ΔH, ΔG, and ΔS) were calculated and discussed. The adsorption of these derivatives on the alloy surface was found to obey Langmuir adsorption isotherm. The electrochemical results are in good agreement with the calculated quantum chemical HOMO and LUMO energies of the tested molecules.

An investigation of the corrosion mechanisms of WE43 Mg alloy in a modified simulated body fluid solution: The effect of electrolyte renewal

The effect of daily electrolyte renewal on the corrosion mechanisms and kinetics of WE43Mg alloy in a modified simulated body fluid (m-SBF) is investigated by electrochemical, hydrogen evolution, analytical and surface characterization techniques. It is shown that by performing electrolyte renewal, physiological control of corrosion products and concentration of relevant electrolyte components such as calcium, phosphate and carbonate species, can be better emulated. Electrolyte renewal affects the corrosion mechanism by promoting partial dissolution of the corrosion layer and increasing mass transport, thereby delaying the increase in the corrosion layer protective ability and the occurrence of localized corrosion.

Inhibition and Adsorption impact of Leave Extracts of &lt;i&gt;Cnidoscolus Aconitifolius&lt;/i&gt; on Corrosion of Aluminium Sheet in 1 M Hcl Medium

Corrosion inhibition in the presence of alokaloid and non alkaloid extracts of Cnidoscolus aconitifolius in 1M HCl was studied using the weight loss and hydrogen evolution techniques at 303, 313 and 333 K. The results obtained revealed that the inhibition efficiency decreased with increase in temperature. Inhibition occurred through adsorption of the alokaloid and non alkaloid extracts molecules on the metal surface. The apparent activation energies, enthalpies and entropies of the dissolution process and the free energies and enthalpies for the adsorption process were determined and discussed. The fundamental thermodynamic functions were used to evaluate important inhibitive properties of Cnidoscolus aconitifolius.Keywords: Activation energy; Gibb’s Free Energy; Langmuir adsorption; Cnidoscolus aconitifolius; Aluminium sheet.