H3PO4 Medium Research Articles

Characterization of modified titanium surfaces by anodisation and immersion tests

This paper explores the features of both nanoporous and compact TiO2 films formed by titanium anodisation in two experimental conditions, given that they have completely different morphologies and properties than those found by our previous studies. After anodisation, samples have been subjected for 20 days to immersion tests in different media (H2O, H3PO4, and KOH). Surface morphology, phase composition and wettability of anodised films were investigated using FESEM, FTIR, Raman spectroscopy, contact angle measurements and XPS, and the hydrophilicity of modified surfaces was investigated by immersion tests. Nanoporous films exhibited hydrophobic surfaces, but contact angle values gradually decreased after immersing films in H2O, H3PO4 and KOH media, respectively. However, compact films produced superhydrophilic surfaces, both before and after immersion tests, with the exception of immersing the film in a H3PO4 medium due to film removal by acid attack. As for compact films, an unusual morphology revealed by the presence of cone-shaped particles might be responsible for the adsorption of –OH groups arranged so as to favour anatase phase formation.

Synthesis and Characterization of Oligomer Bis(<i>trans</i>-2,3-dibromo-4-hydroxy-2-butenyl)terephthalate as a Green Corrosion Inhibitor on Mild Steel in 1 M H<sub>3</sub>PO<sub>4</sub> Solution

Poly(ethylene terephthalate) (PET) waste was depolymerized by trans-2,3-dibromo-2-butene-1,4-diol in the presence of manganese acetate as a catalyst using microwave irradiation as opposed to the conventional heating process in order to reduce the time required for PET depolymerization. The depolymerization product bis(trans-2,3-dibromo-4-hydroxy-2-butenyl)terephthalate (BDBHBT) was isolated, characterized, and evaluated as a green inhibitor for mild corrosion steel in corrosive 1 M H3PO4 medium. This product was characterized using FTIR and 1H-NMR. The effects of immersion time, inhibitor concentration, and reaction temperature were studied. The chemical technique utilized in this study was weight loss, while the electrochemical technique employed an open circuit potential. With 0.6 g/L of BDBHBT inhibitor, the highest corrosion inhibition efficiency of 83.3% was observed. The kinetic and thermodynamic functions were calculated, and the results indicated that the investigated inhibitor was physically adsorbed on the surface and confirmed to the Langmuir adsorption isotherm. This study aims to lessen pollution of the environment by transforming PET waste to a beneficial oligomer BDBHBT and estimating the inhibitory effect of this product on the corrosion of mild steel in 1 M H3PO4.

Electrochemical and spectroscopic analysis of thermochemical conversion of UO2 to UCl3 using AlCl3 and Al in LiCl–KCl eutectic

Thermochemical conversion of UO2 to UCl3 using AlCl3 and Al metal in LiCl–KCl melt at 773 K is reported here. The reaction product was assessed qualitatively by UV–Vis spectroscopy, cyclic voltammetry (CV) and square wave voltammetry (SWV). The extent of conversion efficiency was quantified through UV–Vis spectroscopy by measuring the absorbance of U(VI) at 420 nm after dissolving the reaction product in 1 M HNO3 + 1 M H3PO4 medium. The conversion process was optimized by varying concentrations of AlCl3 (stoichiometric × 1 to 4) and the duration of reactions (45 min–5 h). About 93% conversion of UO2 was achieved by doubling the stoichiometric requirement of AlCl3 in 50 g of LiCl–KCl salt in 2.5 h.

Plant extracts as corrosion inhibitors for mild steel in H2SO4 and H3PO4 media – Review II

Plant extracts as corrosion inhibitors for mild steel in H2SO4 and H3PO4 media – Review II

Inhibition of corrosion of C38 steel in 1 M H3PO4 medium by an esomeprazole drug waste

Inhibition of corrosion of C38 steel in 1 M H3PO4 medium by an esomeprazole drug waste

Iridium(III)-3-hydroxy-2-(3′-methyl-2′-thienyl)-4-oxo-4H-1-benzopyran complex: The analytical, in-vitro antibacterial and DFT studies

The trace determination of iridium(III) has been established using an aqueous phase spectrophotometric approach based upon its tendency to form a complex with the colour generating reagent, 3-hydroxy-2-(3-́methyl-2́-thienyl)-4-oxo-4H-1-benzopyran (HMTB) at pH 4.71–5.11. From 0.005 to 0.05 mol L -1 H3PO4 medium, 1:2 (M:L) light yellow complex between Ir(III) and HMTB has been formed with maximal colour intensity in the wavelength range of 417–425 nm. To optimize the conditions, the effect of several physical parameters such as medium choice and concentration, pH and ligand concentration on the micro level determination of iridium (III) had been examined in depth so as to make the proposed method simple, selective, sensitive and reproducible. Under the ideal set of conditions, the absorbance is linearly proportional to the concentration of Ir(III) in the range 0–1.5 µg mL−1, the correlation coefficient being 0.9954. The molar annihilation coefficient has been evaluated to be 8.458 × 104 L mol−1 cm−1 whereas Sandell’s sensitivity is 0.0023 µg Ir(III) cm−2. The detection limit of the method under the optimal set of conditions is 0.0281 µg mL−1 and relative standard deviation being 0.0296%. The proposed method satisfactorily permits determination of Ir(III) in a variety of synthetic mixtures without any interference. The novelty and advantage of the proposed method is in its high sensitivity in aqueous phase conditions compared to most of the previously cited methods. The molecular structure of the ligand (HMTB) and its complex with Iridium has been investigated using density functional theory calculations at the DFT level of theory. Ionization potential (IP) and Eletron Affinities (EA), Hardness (η), Softness (S), Electronegativity (μ), Electrophilic Index (ω), Electron Donating Power (ω-), Electron Accepting Power (ω+) and Energy Gap (Eg) are some of the molecular characteristics of the title compound that have been calculated. The Ir(III)-HMTB complex is finally tested for its in- vitro antibacterial activity and is found to show significant antibacterial application allowing its use as an antibacterial agent.

Performance of triazole derivatives as potential corrosion in-hibitors for mild steel in a strong phosphoric acid medium: Combining experimental and computational (DFT, MDs & QSAR) approaches

Four Trizaoles (TRi) were investigated as corrosion inhibitors on mild steel (MS) in strong H3PO4 medium by weight loss measurements. TR3 exhibited the highest inhibition activity of 89.47 % at 10−3 M and 308(± 0.5) K. Global and local reactivity descriptors were computed at the DFT/B3LYP/6−31+G** level of theory to evaluate the correlation between the corrosion inhibition activity and the electronic characteristics of TRi. To mimic the real inhibition system (2 M H3PO4), the protonation process of TRi was regarded. Attempts to correlate the theoretical calculations with the observed behaviours showed that the protonation process affected unfavourably the prohibition of TRi. Results demonstrated that the hydration energy (ΔGhyd) may be regarded as a valuable descriptor to inspect the inhibition performance of organic compounds. The Fukui functions and local softness indicated that the azine (=N-N=) link in the triazole ring is the privileged site for the adsorption of the inhibitor. Molecular dynamics (MDs) simulation were exerted to inspect the adsorption geometry of {TRi/50H2O/3H3O+/PO43−/Fe(110)} complexes in the neutral and protonated inhibitory configurations. The outcomes of this work show that TR3 is the pre-eminent inhibitory molecule of the studied systems for both neutral and protonated configurations. The adsorption of TRi was performed spontaneously according to Langmuir's model. The =N-N= moiety in the triazolic ring are the privileged sites of adsorption. The electron-donating substituent (both para-methoxy) effects on the tautomeric mesomeric equilibrium observed on the triazolic ring of TR3 was behind its higher inhibition. QSAR results gave an accurate interdependence between the presaged and experimental research (R² ≈ 1). Coupling GRDs with MDs descriptors enabled to gain further insights into the physical-chemistry of TRi.

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−.

An efficient corrosion inhibitor of cassava starch graft copolymer for aluminum in phosphoric acid

Starch is one of the richest natural polymers with low-cost, non-toxic and biodegradable, but is seldom directly used as corrosion inhibitor due to its poor inhibitive ability and low water solubility. To solve this problem, cassava starch-acryl amide graft copolymer (CS-AAGC) was prepared through grafting acryl amide (AA) with cassava starch (CS), and it was firstly examined as an efficient inhibitor for 1060 aluminum in 1.0 mol·L−1 H3PO4 media. The adsorption behavior of CS-AAGC and its electrochemical mechanism were investigated by weight loss and electrochemical methods. Additionally, the inhibited aluminum surface was fully characterized by a series of SEM, AFM, contact angle measurements and XPS. Results confirm that CS-AAGC performs better inhibitive ability than CS, AA or CS/AA mixture, and the maximum inhibition efficiency of 1.0 g·L−1 CS-AAGC is 90.6% at 20 °C. CS-AAGC acts as a mixed-type inhibitor while mainly retards the anodic reaction. EIS has three time constants, and the polarization resistance is significantly increased in the presence of CS-AAGC. The micrograph of inhibited aluminum surface is of hydrophobic nature with low surface roughness and little corrosion degree.

Use of Omeprazole as Inhibitor for C38 Steel Corrosion in 1.0 M H3PO4 Medium

The importance of the use of various drugs as corrosion inhibitors has developed. In this context, the corrosion inhibition of C38 steel in 1.0 M H3PO4 medium by omeprazole has been evaluated by weight loss tests, potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The surface morphology has been characterized by scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy. The Tafel polarization analysis shows that omeprazole is a mixed-type inhibitor. The results obtained by electrochemical impedance spectroscopy indicate that the inhibition efficacy increases with inhibitor concentration. The results obtained from the standard free energy of adsorption of $$(\Delta {G}_{\text{ads}}^{0}=- 37.86$$ kJ mol−1) are consistent with a physisorption and chemisorption process. The scanning electron microscopy allowed the visualization of a protective layer on the C38 steel surface after the addition of the inhibitor. The results obtained from different tested techniques showed excellent inhibition efficiency up to 99% using omeprazole for C38 steel in a phosphoric acid medium.

Experimental, theoretical and simulation studies of extracted crab waste protein as a green polymer inhibitor for carbon steel corrosion in 2 M H3PO4

Crab waste protein (CWP) has been extracted, characterized and examined as a green polymer inhibitor for carbon steel in 2 M H3PO4 media by weight loss and electrochemical techniques. The inhibition of CWP accelerates by increasing the inhibitor content, but the temperature has hardly affected the inhibition efficiency. Thermodynamic data clearly show that the adsorption mechanism of CWP on the carbon steel surface in 2 M H3PO4 solution is mainly physical adsorption. Moreover, the adsorption of the CWP molecules was found to follow a Langmuir adsorption isotherm. Results of potentiodynamic polarization measurements revealed that the CWP acts as a mixed-type eco-friendly inhibitor. The electrochemical impedance spectroscopy (EIS) technique was employed to pattern the inhibition process through proper equivalent circuit pattern. Theoretical parameters derived from quantum chemical calculations as well as binding energy derived from molecular dynamics simulations experiments adequately corroborate the trend of experimental inhibition efficiencies of the tested inhibitors.

A Comparative Study on Inhibitory Actions of TCE, GIE, and CSE on the Corrosion of 6063 Al Alloy in H3PO4 Medium

Investigations of Terminalia chebula Ritz. extract (TCE), Garcinia indica Choisy extract (GIE), and Coriandrum sativum L. extract (CSE) as corrosion inhibitors for 6063 Al alloy in phosphoric acid (H3PO4) of 0.5 M, 1.0 M, and 2.0 M using potentiodynamic polarization and electrochemical impedance spectroscopy techniques were carried out. The optimal inhibitor concentrations were varied in the temperature range of 30–50 °C at 5 °C interval. Scanning electron microscope/energy-dispersive X-ray spectroscopy (SEM/EDX) technique was used to characterize the coupon surfaces before and after corrosion tests. Inhibition efficiency results with the optimal concentrations of inhibitors were 95.52% for the addition in 0.4 g L−1 of GIE at 50 °C, 91.64% for the addition in 0.4 g L−1 of TCE at 30 °C, and 90.06% for the addition in 0.5 g L−1 of CSE at 30 °C. The activation and adsorption parameters in the presence of inhibitor suggested the adsorption mechanisms were of chemisorption of GIE and physisorptions of TCE and CSE. Langmuir adsorption isotherm was followed. A suitable inhibition mechanism was proposed. The SEM revealed cracks and roughness in the sample without inhibitor, while the surface at an optimal concentration of 0.4 g L−1 of inhibitor had a smooth surface which was accomplished by EDX studies.

Synthesis of cerium orthophosphates with monazite and rhabdophane structure from phosphoric acid solutions in the presence of hydrogen peroxide

It has been proposed to conduct the synthesis of cerium(III) orthophosphates by reacting cerium(IV) compounds with hydrogen peroxide in the presence of concentrated orthophosphoric acid at ambient temperature. It has been shown that the reaction of H2O2 with CeO2 suspensions in H3PO4 medium produces CePO4 · xH2O (rhabdophane structure), while that with CeO2 solutions in concentrated H3PO4 results in CePO4 (monazite structure).

Structure and properties of conducting poly(o-phenylenediamine) synthesized in different inorganic acid medium

Poly(o-phenylenediamine) was chemically synthesized from the monomer o-phenylenediamine in various inorganic acid medium, viz., hydrochloric (HCl), sulphuric (H2SO4) and phosphoric acid (H3PO4) to investigate the differences in structures and properties of the synthesized polymers. From the various characterizations, it was confirmed that the ladder type polymer with some open ring structure was formed in HCl medium while open ring type amine derivative of polyaniline structure was obtained in H2SO4 medium and the ladder type dimer was formed in H3PO4 medium. The structural differences of the polymers were correlated with the polymerization mechanism in different acid medium. Thus, the polymer synthesized in H2SO4 was well soluble in polar organic solvent like dimethyl sulfoxide (DMSO), N,N-dimethyl formamide, tetrahydrofuran etc. and casting of freestanding film was possible from DMSO solution. The highest average DC conductivity of H2SO4 doped polymer synthesized in H2SO4 medium was observed as 7.14×10−4 S/cm. The conductivity and doping properties of the polymer were explained here from the proper characterizations.

Anti-corrosive properties of 4-amino-3,5-bis(disubstituted)-1,2,4-triazole derivatives on mild steel corrosion in 2 M H3PO4 solution: Experimental and theoretical studies

The corrosion inhibitory effect of two 3,5-bis(disubstituted)-4-amino-1,2,4-triazole derivatives, namely 3,5-bis(4-tolyl)-4-amino-1,2,4-triazole (K1) and 3,5-bis(3,4-dimethoxyphenyl)-4-amino-1,2,4-triazole (K2), for mild steel in 2M H3PO4 has been studied using electrochemical impedance spectroscopy (EIS), Tafel polarization curves and weight loss measurements. It was found that the inhibition efficiency of the two investigated inhibitors increases with increase in concentration of inhibitors and decreases with increase in temperature. K1 and K2 show corrosion inhibition efficiency of 80.00 and 86.35%, respectively at 10−3M and 308K. Impedance experimental data revealed a frequency distribution of the capacitance, simulated as constant phase element. Potentiostatic polarization study showed that K1 and K2 are mixed-type inhibitors in 2M H3PO4. The results obtained from electrochemical and weight loss studies were in reasonable agreement. The adsorption of K1 and K2 on steel surface obeys Langmuir's adsorption isotherm. The correlation between inhibition efficiency and molecular structure of the inhibitors is investigated by determination of chemical indexes, which were performed using density functional theory (DFT) at (B3LYP/6-31G) (d,p) level. Monte Carlo simulations were further performed to simulate the adsorption of K1 and K2 on Fe (110) surface in the presence of water and the results show that K2 is more effective as corrosion inhibitor for mild steel in 2M H3PO4 medium than K1.

Experimental, quantum chemical and Monte Carlo simulation studies of 3,5-disubstituted-4-amino-1,2,4-triazoles as corrosion inhibitors on mild steel in acidic medium

The inhibition properties of two 3,5-bis (disubstituted)-4-amino-1, 2,4-triazole derivatives, namely 3,5-bis(4-methoxyphenyl)-4-amino-1,2,4-triazole (T1) and 3,5-bis(4-chlorophenyl)-4-amino-1,2,4-triazole (T2) were investigated for mild steel corrosion in 2M H3PO4 medium at 308K using electrochemical impedance spectroscopy (EIS), Tafel polarization curves and weight loss measurements. The results showed that the 4-amino-1, 2,4-triazole derivatives (T1 and T2) were good inhibitors in 2M H3PO4, and the inhibition efficiency, η(%), increased with the inhibitor concentration but the temperature had no effect on the inhibition efficiency. The adsorption of T1 and T2 on the mild steel surface obeyed Langmuir's adsorption isotherm. Both thermodynamic and kinetic parameters were calculated and discussed. Data obtained from EIS studies were analysed to model inhibition process through appropriate equivalent circuit model. Potentiodynamic polarization curves revealed that T1 and T2 behave as mixed-type inhibitors. The adsorption behaviour of the 4-amino-1, 2,4-triazole derivatives on Fe (110) surface was investigated by Monte Carlo simulations in the presence of water to verify their corrosion inhibition efficacies. The results indicated that the adsorption energy of T1 was greater than T2, which is in accordance with the experimentally determined inhibition efficiency.

Standardization of in vitro skin corrosion test using reconstructed human epidermis tissues (RhE Model)

The corrosion inhibitory effect of two 3,5-bis(disubstituted)-4-amino-1,2,4-triazole derivatives, namely 3,5-bis(4-tolyl)-4-amino-1,2,4-triazole (K1) and 3,5-bis(3,4-dimethoxyphenyl)-4-amino-1,2,4-triazole (K2), for mild steel in 2 M H3PO4 has been studied using electrochemical impedance spectroscopy (EIS), Tafel polarization curves and weight loss measurements. It was found that the inhibition efficiency of the two investigated inhibitors increases with increase in concentration of inhibitors and decreases with increase in temperature. K1 and K2 show corrosion inhibition efficiency of 80.00 and 86.35%, respectively at 10− 3 M and 308 K. Impedance experimental data revealed a frequency distribution of the capacitance, simulated as constant phase element. Potentiostatic polarization study showed that K1 and K2 are mixed-type inhibitors in 2 M H3PO4. The results obtained from electrochemical and weight loss studies were in reasonable agreement. The adsorption of K1 and K2 on steel surface obeys Langmuir's adsorption isotherm. The correlation between inhibition efficiency and molecular structure of the inhibitors is investigated by determination of chemical indexes, which were performed using density functional theory (DFT) at (B3LYP/6-31G) (d,p) level. Monte Carlo simulations were further performed to simulate the adsorption of K1 and K2 on Fe (110) surface in the presence of water and the results show that K2 is more effective as corrosion inhibitor for mild steel in 2 M H3PO4 medium than K1.

Research on Corrosive Wear Properties of Super High Chromium Cast Iron

National standard high chromium cast iron contains 26% chromium by weight (Cr26). A new type of Super High Chromium Cast Iron (SHCCI) has been developed with chromium content of about 37% by weight. This paper examines the microstructure of SHCCI using SEM and XRD. The hardness and toughness of SHCCI was studied and the corrosive wear properties of SHCCI were also examined using an MCF-30 type erosion abrasion tester under H3PO4 media. The results show that, the microstructure of SHCCI is composed of M7C3 and M23C6 carbides, martensite matrix and residual austenite matrix. With proportionately greater carbon content, the hardness of SHCCI will first increase and then decrease, while the toughness and corrosive wear properties will decrease gradually SHCCI’s corrosive wear performance was significantly better than that of Cr26 cast iron. The maximum wear capacity of SHCCI is three times higher than that of Cr26 cast iron.

Extraction of uranyl ion from nitric acid medium using solvent containing TOPO and its mixture with D2EHPA in room temperature ionic liquids

Studies on the extraction of uranyl ion were carried out from nitric acid feed solutions using solutions of tri-n-octyl phosphine oxide (TOPO) in several room temperature ionic liquids (RTIL), viz. [C4mim][PF6], [C6mim][PF6], [C8mim][PF6], [C4mim][NTf2], [C6mim][NTf2], [C8mim][NTf2]. All solvent extraction studies used 0.05M TOPO in the respective RTILs. Out of the RTILs studied, those containing C8mim+ as the cationic part showed significantly higher extraction efficiency. The ionic liquids with PF6− as the counter anion showed faster extraction kinetics as well as higher extraction efficiency as compared to those containing NTf2− as the counter anion. The extraction studies carried out at varying concentrations of nitric acid indicated solvation mechanism of extraction similar to that displayed with molecular diluents such as n-dodecane. The extracted species were ascertained from the slope analysis method which indicated 1:2 (metal:ligand) ratio in the complex which displayed variations with the feed nitric acid concentration. UV–visible and fluorescence spectroscopic studies were also carried out to understand the nature of the extracted species.Solutions of D2EHPA and its mixture with TOPO in the RTILs were also used for the extraction of U(VI) from both HNO3 as well as H3PO4 medium. While the solvent system containing D2EHPA+TOPO in RTILs do not show appreciable variation with HNO3 concentration, a sharp decrease was seen with increasing H3PO4 concentration.

The protective effect of polypyrrole coating on the corrosion of steel electrode in acidic media

In this study, the corrosion parameters of stainless steel containing 12% Cr, have been determined by Tafel extrapolation method in 1 M HCl, H2SO4 and H3PO4 media. Later, steel was coated with polypyrrole in 0.1 M Pyrrole + 0.3 M Oxalic acid solution by cyclic voltametric method. The corrosion parameters and percentage inhibition efficiencies of coated electrodes were investigated according to immersion times in the same media. In all acidic media studied, increases in immersion time, produced increased corrosion densities and a decrease in percentage inhibition efficiencies were determined.