Uninhibited Solution Research Articles

Evaluation of cactus mucilage as a green corrosion inhibitor for copper in sulfuric acid environment

This study investigates the corrosion inhibition performance of cactus mucilage for copper in 0.5 M H2SO4 solution. The cactus mucilage was extracted using a pure water extraction method and characterized using FTIR and GC-MS analyses. The inhibition efficiency was evaluated using potentiodynamic polarization and EIS techniques, while surface morphology was analyzed using SEM and AFM. The potentiodynamic polarization results revealed that cactus mucilage acts as a mixed-type inhibitor, with inhibition efficiency increasing from 78.6% at 100 mg L-1 to 94.5% at 600 mg L-1. The EIS measurements showed a significant increase in charge transfer resistance from 0.56 k? cm-2 in the uninhibited solution to 8.26 k? cm-2 with 600 mg L-1 cactus mucilage. The adsorption of cactus mucilage on the copper surface followed the Langmuir isotherm model, with a strong adsorption equilibrium constant of 23.6 × 103 M. Compared to other green inhibitors, cactus mucilage exhibited superior inhibition efficiency and sustainability advantages, making it a promising eco-friendly alternative for copper corrosion protection.

An Exploratory Experimental Analysis Backed by Quantum Mechanical Modeling, Spectroscopic, and Surface Study for C-Steel Surface in the Presence of Hydrazone-Based Schiff Bases to Fix Corrosion Defects in Acidic Media.

This work focuses on developing corrosion control and protecting the environment by creating affordable, sustainable, environmentally friendly, and efficient corrosion resistance chemicals. That is, through synthesized three hydrazone Schiff bases E-2-(1-hydrazonoethyl)thiazole (HTZ), 2-((E)-(((Z)-1-(thiazol-2-yl)ethylidene)hydrazono)methyl)phenol (HTZS), and 2-((E)-(((Z)-1-(pyridin-2-yl)ethylidene)hydrazono)methyl)phenol (HPYS) and corrosion inhibitors for C-steel in 8 M H3PO4 solution that were studied. The chemicals were analyzed by using 1H NMR and 13C NMR spectroscopy to learn more about them. Predominantly, the hydrazone-based Schiff bases have been considered powerful inhibitors due to their ability to be adsorbed with very low concentrations through their reactive sites (N, O, and S). Maximum surface (θmax) coverage and inhibition efficiency of 83.33% were sufficiently found at 99.00 × 10-3 mol/L concentration of HTZS at 293 K. Galvanostatic experiments demonstrated that raising the concentration of hydrazones improved mass transfer resistance. To study microstructure, scanning, reflectance, and energy-dispersive X-rays were used. Roughness and qualitative adhesion of the adsorbed layer were estimated by an atomic force microscope. After adding 99.00 × 10-3 mol/L of HTZS, the degree of surface brightness and reflectance increases to 137.20, relative to the corroded electrolyte-free solution 27.70. The roughness (Ra) decreased from 0.468 to 0.088 μm by adding HTZS. A surface morphology study confirmed that adding hydrazones to the C-steel dissolution bath greatly improves the surface's look and texture quality. The atomic absorption spectroscopy technique was used to compare the concentration of the iron ions that remained in the solution after galvanostatic analysis in the absence and presence of the hydrazones under different conditions; it was found that the inhibited solution contained lower concentrations of iron ions as compared to the uninhibited solution. The DFT theoretical analysis verified the observation of hydrazone physical adsorption through bonding electrons that obey kinetic adsorption isotherms. It is based on examining the highest occupied molecular orbital-lowest occupied molecular orbital (HOMO-LUMO), the Fukui functions, and the Mulliken atomic charge. Overall, the results suggest that HTZS is a good corrosion inhibitor with a large surface area due to the presence of S, N, and O atoms, allowing for creating a larger surface due to the large molecular volume of atoms protecting against the corrosion process.

1-(Tert-Butoxy)Propan-2-Amine and It's Efficacy Towards Corrosion Inhibition of Mild Steel in Marine Environment – Experimental Study

The alloy of iron has wide applications in industries ranging from health to construction sector. The mild steel is the most sought alloy of iron in industries and is preferred due to its low cost and better mechanical properties. Even though mild steel possesses high mechanical strength it may readily undergo corrosion during its usage in adverse environments. Therefore, in the present research an effort was made to improve the inhibition of mild steel corrosion in the presence of chloride ions using 1-(tert-butoxy)propan-2-amine. The mild steel samples were initially investigated for weight loss measurements to assess the state of mild steel in different concentrations of 1-(tert-butoxy)propan-2-amine and later subjected to electrochemical studies using Tafel polarisation and Electrochemical Impedance Spectroscopy (EIS) to know the corrosion state when exposed to inhibited and uninhibited solutions of 3.5% NaCl. The microstructural characterisation using Scanning Electron Microscopy (SEM) analysis gives the surface micrographs of the mild steel subjected to corrosion and inhibition. The inhibitor is found to perform better with high inhibition efficiency from above tests when compared to the uninhibited solution and is a clear indication of the corrosion inhibiting property of the employed inhibitor. The presence of π-electrons on heteroatoms in the employed organic inhibitor is the main reason for the inhibition efficiency and effective adsorption on the mild steel surface.

Investigation of the inhibition behavior of an octacalcium phosphate as a green corrosion inhibitor against carbon steel in 3 % NaCl medium

The development of new corrosion inhibitors constitutes a significant endeavor for researchers. In this study, the efficacy of octacalcium phosphate (OCPa), an inorganic green corrosion inhibitor for carbon steel in a 3% NaCl solution, was evaluated. This investigation marks the first application of this compound in a saline environment. The phosphate inhibitor was synthesized through a double aqueous decomposition process in an equimolar solution of water and ethanol, and subsequently characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), chemical analysis, and SEM/EDX to ascertain its properties and morphology. Meanwhile, the electrochemical behavior was investigated using techniques such as potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) to assess the anticorrosive performance of the studied phosphates. Analysis of the carbon steel surface morphology of the resultant layer was conducted using SEM/EDX and FTIR. According to the electrochemical results, OCPa demonstrated an impressive inhibitory effect, with an efficiency reaching 93.1% at an optimal concentration of 50 ppm, exhibiting a cathodic type of inhibition. Moreover, the charge transfer resistance was found to be 2450 Ω.cm2 in the presence of 50 ppm of the inhibitor, as compared to 161.0 Ω.cm2 in the uninhibited solution. The thermodynamic parameters indicated an endothermic nature for the adsorption process in the presence of OCPa. Examination of the carbon steel surface morphology by SEM revealed the formation of a protective layer, serving to shield the metal from corrosion. The experimental findings underscore the potential of octacalcium phosphate as a promising inorganic green corrosion inhibitor for carbon steel in saline environments, opening new avenues for the exploration and development of environmentally benign anti-corrosive substances.

The effect of functional groups on the inhibitory efficacy of newly synthesized Imidazopyridines compounds against the corrosion of mild steel in acidic environments: Electrochemical, thermodynamic, surface and computational investigations (Part B)

The primary objective of this research paper was to investigate the inhibitory effects of two new derivatives of Imidazopyridines, namely: (E)-N-(7-methyl-2-phenylimidazo[1,2-a]pyridin-3-yl)-1-(3-nitrophenyl)methanimine (N-Imid) and (E)-2‑methoxy-4-(((7-methyl-2 phenylimidazo[1,2-a]pyridin-3-yl)imino)methyl)phenol (MH-Imid), on mild steel (MS) in 1 M hydrochloric acid at 308 K. The study also aimed to compare the protection capacities of these compounds. Additionally, the impact of (-OH & OCH3–) and (-NO2) groups on the inhibition efficiency was analyzed. The inhibition performance was measured using potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) and weight loss (WL) methods at 308 K, and confirmed by Scanning Electron Microscopy (SEM),UV–visible, and computational modeling, The study results showed that the both inhibitors displayed potent inhibition capacities, and their effectiveness grew notably with rising concentration and diminishing temperatures. Among the two compounds investigated, MH-Imid is the best with an inhibition efficiency over 96%. The substitution of functional groups was found to influence the inhibition efficiency. The electrochemical tests findings were consistent. The outcomes indicated that both inhibitors exhibited cathodic/anodic behavior (mixed type). SEM analysis was used to assess the surface morphology and showed the presence of a protective layer on the MS surface, The two studied inhibitors were adsorbed on the MS surface by the Langmuir adsorption model. Analysis of the inhibited and uninhibited solution using UV-visible spectroscopy showed evidence of a complex between Fe and two imidazopyridine molecules forming in 1 M HCl. The computational modeling matches experimental data well and demonstrates that the inhibition efficiency ranking (MH-Imid > N-Imid) holds consistently.

Corrosion inhibitory potential of selected flavonoid derivatives: Electrochemical, molecular⋅⋅⋅Zn surface interactions and quantum chemical approaches

Zinc metal corrosion inhibitor potential of some flavonoid derivatives, namely, naringenin (NRNG), morin hydrate (MNHD), and 6-hydroxyflavone (6-HFN), was investigated by measuring their inhibitory activities, determining their thermodynamic and kinetic adsorption mechanistic properties as well as comparing their molecular⋅⋅⋅Zn metal surface interaction strengths. The inhibition efficiencies were evaluated in 1.5 M hydrochloric acid (HCl) environment and different concentrations of the inhibitors (from 2.0 × 10−4 – 1.8 × 10−3 M) using gravimetric and various electrochemical methods at 30–60 °C. The molecular···metal surface interactions were determined using the density functional theory method by using the GGA/RPBE/DNP approach. Electrochemical studies show that 6-HFN and NRNG are the most and least effective corrosion inhibitors, with 77.54 and 70.46 maximum percentage inhibition efficiency, respectively. Atomic Absorption Spectroscopy technique was used to compare the concentration of the zinc ions that remained in the solution after gravimetric analysis in the absence and presence of the inhibitors at 30 °C; it was found that the inhibited solution contained less concentrations of zinc ions as compared to the uninhibited solution. Surface morphology techniques (e.g., 3D microscope) suggest that a localised type of corrosion took place on the metals, and the corrosion damage was minimal in the presence of the inhibitors. FT-IR showed a strong adsorption of the functional groups found in the inhibitor compounds, with CC functional group being strongly retained by all three inhibitors. The flavonoid inhibitor compounds were found to absorb chemically at low temperatures and physically at high temperatures. Langmuir adsorption isotherm was obeyed. The trend for molecular···metal surface interaction strengths follows the trend obtained from experimental findings on inhibition efficiency. Overall, the results suggest that all the molecules investigated are good corrosion inhibitors with a preference for those compounds in which there exists extended electron delocalization through the aromatic rings and in which there are minimal electron-withdrawing groups on the aromatic rings.

Effectiveness of strontium zinc phosphosilicate on the corrosion protection of AA2198-T851 aluminium alloy in sodium chloride solution

The effectiveness of strontium zinc phosphosilicate (SZP 391) as a corrosion inhibitor for the protection of Al–Cu–Li alloy in 0.5 M NaCl solution was evaluated using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation (PDP). The morphology of substrates were characterised with scanning and transmission electron microscopy (SEM) and (TEM). The corrosion rate of the substrates exposed to uninhibited solution increases with immersion time while those in inhibited solution showed significant reduction of corrosion rate. SEM and TEM revealed presence of film formed on the substrates’ surface which serves as a barrier for blocking the access of aggressive ions.

Corrosion Inhibition Effect of Pyridine-2-Thiol for Brass in An Acidic Environment.

In this study, the inhibitive performance of pyridine-2-thiol added to a corrosive solution was investigated for brass using potentiodynamic polarization, electrochemical impedance spectroscopy, and X-ray photoelectron spectroscopy. Electrochemical experiments were performed with different inhibitor concentrations in 0.5 M H2SO4 as the corrosive medium. For potentiodynamic polarization, icorr values decreased significantly for the inhibited solutions in contrast with the uninhibited solution. Pyridine-2-thiol had an optimum inhibition concentration of 0.25 mM, giving an icorr value of 1.8 µA/cm2 compared to 26 µA/cm2 for the blank solution. EIS data indicated that Rp and Rct values increased substantially after the addition of the corrosion inhibitor and corrosion inhibition efficiencies of more than 85% was achieved for the majority of the inhibited solutions. Scanning electron microscopy showed defect free and less scale formation for the inhibited surface but the bare brass surface had larger amounts of scale formation. X-ray photoelectron spectroscopy and UV-vis spectroscopy was used to investigate surface chemical composition and inhibitor structural changes over time.

Synthesis, spectroscopic, and density functional theory studies of the corrosion inhibitive behaviour of n-(1,4-dihydro-1,4-dioxonaphthalene-3-yl)pyrazine-2-carboxamide chelator-ligand

The inhibitory effect of N-(1,4-dihydro-1,4-dioxonaphthalene-3-yl) pyrazine-2-carboxamide (HL chelator) on the corrosion of mild steel (Ms) in 1M HCl remained appraised via weight loss (WL) estimations, atomic absorption spectrophotometer (AAS), scanning electron microscope (SEM) and computational studies. The adsorption of the appraised ligand remained found to conform to Langmuir adsorption isotherm (LAI). The data acquired for ΔGads denotes chemisorption adsorption mechanism for the inhibitor while acquired AAS analysis results revealed that the concentration of iron in the inhibited corrosive medium is less than the concentration of iron in the uninhibited solution after immersion with Ms at the same contact time and was also observed to reduce with upsurge in concentration of the inhibitor. SEM micrographs acquired revealed that the existence of the studied compound lessened the degree of corrosion in addition to decreased surface roughness signifying establishment of protective inhibitor film at the Ms surface. The energy of highest occupied molecular orbital (EHOMO) as well as energy of lowest unoccupied molecular orbital (ELUMO) remained estimated via density functional theory (DFT) method from which other parameters were determined. The results acquired from computational studies were in conformity with those from experimental studies and both validate the use of HL chelator as an excellent and efficient inhibitor for the corrosion of Ms in 1 M HCl.

Amphoteric surfactant of octadecyl dimethyl betaine as an efficient corrosion inhibitor for cold rolled steel in phosphoric acid solution

The inhibition effect of amphoteric surfactant of octadecyl dimethyl betaine (BS-18) on cold rolled steel (CRS) in H3PO4 solution was studied by weight loss, electrochemical technique, surface analysis and quantum chemical calculations. The results show that BS-18 acts as an efficient inhibitor on CRS in 1.0 M H3PO4 medium at 20–50 °C, and the maximum inhibition efficiency is 87.1% with 50 mg L−1 at 20 °C. Its adsorption on steel surface obeys Langmuir adsorption isotherm, which is endothermic process accompanying with the increase of entropy. Compared with uninhibited solution, apparent activation energy, pre-exponential factor, activation enthalpy and activation entropy become higher in inhibited solution, while both reaction constant and rate constant decrease after adding BS-18. Inhibition performance remains more stable from 3 to 48 h, and fluctuates slightly with the acid concentration from 0.5 to 5.0 M. BS-18 is a mixed-type inhibitor through “geometric blocking effect”. EIS is a time constant with one depressed capacitive loop in Nyquist plot and one phase angle in Bode phase plot, and the charge transfer resistance turns to become more larger in the presence of BS-18. SEM and AFM micrographs of inhibited CRS surface appear little corrosion, and its contact angle is increased. There are functional groups of C–N and C–N+ in the adsorptive film of BS-18 on CRS surface using XPS analysis. Critical micelle concentration (CMC) of BS-18 is about 20 mg L−1 from surface tension measurements. Quantum chemical calculations confirm that the active adsorption site of BS-18 is the hydrophilic group of N+ and –CH2COO−.

Adsorption and corrosion inhibition accomplishment for thiosemicarbazone derivatives for mild steel in 1.0 M HCl medium: Electrochemical, XPS and DFT studies

Four benzaldehyde thiosemicarbazone derivatives namely as 2-benzylidene-N-phenylhydrazinecarbothioamide (L1), 2-(4-hydroxybenzylidene)-N-phenylhydrazinecarbothioamide (L2), 2-(4-chlorobenzylidene)-N-phenylhydrazinecarbothioamide (L3), and 2-(4-methylbenzylidene)-N-phenylhydrazinecarbothioamide (L4) were successfully synthesized and elucidated by physical and spectral techniques, to be specific, melting point, elemental analysis (CHNS), infrared spectroscopy (FTIR) and 1H and 13C nuclear magnetic resonance spectroscopy (NMR). These organic corrosion inhibitors behaviour for mild steel (MS) in 1.0 M HCl solution was examined using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. From the electrochemical measurements, most ligands behave as efficient inhibitors for the MS in 1.0 M HCl solution which contribute the maximum inhibition efficiency up to 93.38% for L3. The potentiodynamic polarization measurements unfolds each synthesized compound were mixed-type inhibitor based on the shifting of corrosion potentials (Ecorr) found to be lesser than ±85 mV. The electrochemical impedance spectroscopy (EIS) analysis revealed retardation of metal corrosion succeeded by cause of adsorption of the four thiosemicarbazone derivatives inhibitor molecules at the metal/solution interface. The adsorption of thiosemicarbazone molecules on the low carbon steel surface in 1.0 M HCl solution obeys Langmuir adsorption isotherm. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) demonstrates in the presence of optimum concentration of L1-L4 inhibitors at 0.04 mM indicates greatly reduced surface roughness of MS in comparison with uninhibited solution. The findings were further reinforced via surface elemental analysis of metal/solution interface via X-ray Photoelectron Spectroscopy (XPS), which unveils L3 exhibit the greatest inhibition efficiency. The most plausible reason is due to benzene rings in the molecular structure increases the adsorption ability in supporting the substituent of chloro as well as conjugated double bond of C=N and C=S that chemisorbed along the surface of metal. The oxide species of FeO, Fe2O3 and FeOOH found to be chemisorbed and physisorbed on MS surface. The impact of molecular properties on the corrosion inhibition and the adsorbed sites of L1-L4 on the metal were investigated using density functional theory calculations (DFT) at the B3LYP/6–311 + G (d,p) level of theory. From the Frontier Molecular Orbitals (FMO), the Highest Occupied Molecular Orbitals (HOMO) discloses adsorption of L2 on the MS surface generally due to 2-(4-hydroxybenzylidene)-N-hydrazinecarbothioamide, whereas for L1, L3 and L4 associated to the inclusion of phenyl carbothioamide. The Lowest Occupied Molecular Orbitals (LUMOs) of L1-L4 are comparatively resembling and delocalized of all molecules. DFT reveals protonated thiosemicarbazones exhibits high correlations coefficients as up to 99–100% in comparison to the corresponding neutral forms of the molecules. The increase in the inhibition efficiency of protonated L1, L2 and L3 is proportional to the ∆N and DM.

Paederia Foetida Leaves Extract as a Green Corrosion Inhibitor for Mild Steel in Hydrochloric Acid Solution

Corrosion causes heavy damages to our machines and structures. Every year billions of dollars are wasted because of this. Much corrosion protective measured are applied to protect the metal which are harmful for the environment. Green corrosion inhibitors are alternative approach in this regard. In this research, Paederia Foetida leaves extract has been used as a green corrosion inhibitor along with mild steel as a sample and 1M hydrochloric acid as an acid solution. The inhibited solution has been prepared by mixing the Paederia Foetida leaves extract with hydrochloric acid. Mild steel samples have been immersed in both inhibited and uninhibited solution for 3, 5 and 7 days. The corrosion efficiency is measured by the weight loss measurement and the maximum efficiency is obtained after 3 days of emersion which is about 73.77%. The FTIR spectroscopy test reveals that the formed adsorbed protective layer protects mild steel surface from corrosion after immersion in inhibited solution. The SEM shows the surface morphology of the corroded surface where smooth surface of immersed mild steel in inhibited solution due to formation of protective biofilm upon the mild steel surface by the physical adsorption process is seen. For further analysis, surface topography and particle analysis have been performed. At the end, mechanism of inhibition is explained with equation.

Corrosion of structural constituents of 2017 aluminium alloy in acidic solutions containing inhibitors

AbstractThe objective of this study is to establish the corrosion behaviour of the most important structural constituents of the aluminium alloy 2017 in orthophosphoric acid solutions containing heteropolyoxomolybdate, tungstate and vanadate. These are potential candidates for replacing toxic hexavalent chromium species in stripping solution for anodic coatings. The corrosion rate of the alloy is estimated with linear polarisation method. It decreases from 0.58 mA cm−2 in uninhibited solution to 0.10 mA cm−2 in a solution containing heteropolyoxomolybdate species. Microscopic studies reveal that heteropolyoxomolybdate species inhibit corrosion of the matrix and intermetallic Al15(Fe,Mn)3(Si,Cu)2 but not Mg2Si. Intermetallic Al2Cu remains not corroded. Heteropolyoxotungstate species virtually do not inhibit the corrosion of the alloy. The solution containing vanadium species is not stable with time and the corrosion rate is not determined. Nevertheless, corrosion of the matrix is inhibited, but intermetallics Al15(Fe,Mn)3(Si,Cu)2 together with Mg2Si are dissolved. X‐ray photoelectron spectroscopy is used for examination of a corrosion product precipitated on the surface.

Experimental and theoretical studies of azomethines derived from benzylamine as corrosion inhibitors of mild steel in 1 M HCl

Two azomethine ligands derived from 2,4-dihydroxybenzaldehyde and benzylamine derivatives were successfully synthesized through the conventional condensation method. The physicochemical properties were elucidated using elemental analysis (CHNS), infrared spectroscopy (IR) and nuclear magnetic resonance spectroscopy (NMR). The corrosion retardation outcomes of two azomethines derived from benzylamine namely as A1 and A2 for the low carbon steel in 1 M HCl at dissimilar concentrations were studied based on polarization measurement and electrochemical impedance spectroscopy (EIS). Based on the impedance results, it shows that an increase in the additives concentration will simultaneously increases the resistance of charge transfer while reducing double-layer capacitance. The polarization measurement parameters proved that in the existence of inhibitors, corrosion potential (Ecorr) has been altered in the direction of the cathodic region as compared to uninhibited solution and obeys Langmuir adsorption isotherm. A1 and A2 additives are regarded as mixed-type inhibitors since the corrosion potential shifts are less than ±85 mV as comparison to the corrosion potential in the absence of inhibitors’ solution. Based on the electrochemical measurement, A2 shows up to 95% inhibition efficiency. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed improvement of metal substrate at the interface of metal/solution with the presence of A1 and A2 inhibitors. From the density-functional theory study (DFT), A2 inhibitor improved inhibition efficiency due to strong solubility in water as opposed to A1. The presence of fluorine in A2 causes the frontier orbitals of HOMO more delocalized than A1, thus increase the adsorption of whole molecule to the interface of metal/solution, which also explain improved inhibition efficiency as compared to A1. The findings were supported with further investigation based on the elemental composition analysis of interface of metal/solution using X-ray Photoelectron Spectroscopy (XPS). Based on the XPS analysis, the adsorption of A2 inhibitor on mild steel-electrolyte interface has been proved mostly via chemisorption from carbon as found in the benzene ring and physisorbed via nitrogen in CN+.

Effect of Microstructure of X-120 Steel on CO2 Corrosion Inhibition by 2-Mercaptobenzimidazole

The use of 2-mercaptobenzimidazole (2MBI) as corrosion inhibitor for API X-120 pipeline with two different microstructures in a CO2-saturated 3.5% NaCl solution has been investigated. One microstructure was predominantly martensitic and bainitic (steel A), whereas the second one was mainly ferritic (steel B). It was found that 2MBI behaved as a mixed type of corrosion inhibitor and it changed the corrosion-controlled mechanism. In the uninhibited solution, steel A had a dissolution rate higher than steel B. However, in the presence of inhibitor, dissolution rate for steel A was lower than that for B because the film-formed inhibitor is adsorbed in a better way for steel A which has smaller precipitates distributed in a more homogeneous way than that for steel B.

The Electrochemical Behavior of Al Alloys in NaCl Solution in the Presence of Pyrazole Derivative

This paper studies the corrosion inhibition of Al-Mg alloy system in 0.5 mol/dm3 NaCl solution in the presence of pyrazole derivative using potentiodynamic polarization and linear polarization method. The inhibition efficiency as a function of concentration and temperature was investigated. From the polarization curves, it can be concluded that the pyrazole derivative behaves like a mixed inhibitor. It has been shown that the efficiency of the inhibitor increases with increasing concentration and with increasing temperature and it indicates a chemisorption process. It was concluded that the pyrazole derivative adsorbed on the electrode blocks the active surface sites and reduces the corrosion rate. The kinetic and thermodynamic parameters of the adsorption process were determined. The relatively low efficiency of the inhibitor at room temperature could be an indicator of increased desorption in the adsorption-desorption equilibrium process. With increasing temperature the equilibrium is shifted in the direction of adsorption, causing an increasing inefficiency. Also, the positive values of equilibrium adsorption constant Kads indicate chemisorption of the pyrazole derivative on the alloy surface. The values of the activation energy in the presence of inhibitor were lower than in the uninhibited solution, which also indicates the chemical adsorption. Negative values of adsorption free energy ΔGads show that the adsorption process is spontaneous.

Continuous Studies on Using Camel’s Urine as Nontoxic Corrosion Inhibitor–Corrosion Inhibition of Al–Cu Alloy in Alkaline Solutions

The corrosion inhibition of Al–Cu alloy in 0.5 M NaOH using various concentrations of camel urine (CU) was investigated using hydrogen evolution, weight loss, electrochemical impedance spectroscopy and potentiodynamic polarization measurements. Analysis of impedance spectra revealed that CU inhibits the corrosion of the studied alloy effectively through the formation of a protective film on its surface with a resistance increasing with increasing CU concentration. Polarization studies indicated that CU was a mixed-type inhibitor except for CU concentrations > 3 mL% where it behaves predominantly as an anodic inhibitor. Hydrogen evolution plots were analyzed using shrinking core models for solid–liquid heterogeneous systems. The resultant data revealed that after certain induction period, hydrogen evolution occurs by fast reaction followed by slow reaction and the latter is controlled by diffusion. The values of IE% obtained from hydrogen evolution and weight loss measurements were temperature dependent. Generally, the inhibitor performance decreased at relatively high temperature (60 $$^{\circ }$$ C) except for low CU concentrations (< 3 mL%) the inhibition efficiency improved with temperature increase. The apparent activation energy for Al–Cu alloy corrosion in the inhibited solutions was calculated and compared with that in the uninhibited solution. El-Awady and Temkin adsorption isotherms fit well the adsorption data obtained from weight loss at 30 $$^{\circ }$$ C and 60 $$^{\circ }$$ C. Based on El-Awady and Temkin isotherms, multilayer film formation with repulsive forces between the adsorbed molecules was suggested. Various thermodynamic parameters for the adsorption process were calculated and discussed. Thermodynamic data indicated comprehensive adsorption (chemisorptions and physical adsorption). Good assessment to correlate the inhibition mechanism with the CU composition was obtained.

A study on the effect of new prepared amide cationic amphipathic on the corrosion inhibition of API N80 steel pipelines in oil wells industries

PurposeThe purpose of this study is to inspect the corrosion inhibition of API N80 steel pipelines in uninhibited solution and inhibited with a synthesized surfactant compound [N-(3-(dimethyl octyl ammonio) propyl) palmitamide bromide] (DMDPP), which is prepared through a simple and applicable method.Design/methodology/approachWeight loss was inspected at five different temperatures of 25°C, 30°C, 40°C, 50°C and 60°C Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation were used at room temperature. Density functional theory was used to study the relation between the molecular structure and inhibition theoretically.FindingsAdsorption of the prepared DMDPP fits the Langmuir isotherm model. The inhibition efficiency of the prepared DMDPP amphipathic inhibitor is directly proportional to temperature increase. Polarization results reveal that the investigated DMDPP amphipathic compound behaves as a mixed-type inhibitor. EIS spectra produced one individual capacitive loop.Originality/valueThe originality is the preparation of cationic surfactants through a simple method, which can be used as corrosion inhibitors in oil production. The synthesized inhibitors were prepared from low-price materials. The work studied the behavior of the synthesized surfactants in inhibiting the corrosion of the steel in an acidic medium. Electrochemical and theoretical studies were presented, besides gravimetric and surface examination.

The replacement of chromate by molybdate in phosphoric acid-based etch solutions for aluminium alloys

ABSTRACTCorrosion inhibition of aluminium alloys in the acidic solutions is important in the aluminium finishing industry (stripping solutions for anodic films). Sodium molybdate is a potential replacement for chromate-containing species used in the stripping solutions. It was tested as the corrosion inhibitor of 2024 aluminium alloy in orthophosphoric acid solutions. A corrosion rate of the alloy as a function of an initial concentration of sodium molybdate and temperature was determined by using gravimetric and gasometric methods. The corrosion rate was significantly lower in the solutions containing over 5 mM of sodium molybdate when compared to the uninhibited solution. The inhibition efficiency decreased with the increase of the temperature for the constant concentration of sodium molybdate. Sodium molybdate reduced the corrosion of the alloy by adsorption as well as formation of insoluble corrosion products on the alloy.

Evaluation of Inhibitive Performance of Acidic Extract of Eichornia Crassipeson Corrosion of Low Carbon Steel in 1M Sulphuric Acid Solution

Corrosion inhibition potential of Eichhornia crassipes extract on low carbon steel in 1 M sulphuric acid solution was investigated using gravimetric method and corrosion rate. The experiment was carried out for 3 hours at different concentration of Eichhornia crassipes extract and temperatures of 26.6°C, 40°C and 60°C. Arrhenius and improved Arrhenius equations were used to determine the thermodynamics properties of the reaction while the nature of the reaction was proposed by adsorption isotherms. The results showed that corrosion rate decreased in the presence of the extract except in 60oC. Inhibition efficiency also increased with extract concentration with the highest (82%) occurring at room temperature and 5% concentration. Inhibition efficiency decreased with increase in temperature with almost no inhibition at 60oC, this is associated with physisorption. Activation energy () and activation enthalpy () both had positive values and they increased in the presence of Eichhornia crassipes extract, those for inhibited solution were higher than those for uninhibited solution, these can also be attributed to physisorption. Inhibition reaction obeyed Langmuir adsorption isotherm. Gibbs free energy () calculated for the reaction is -8.509 to -11.767 kJ mol-1.