An electroactive co-polymer as corrosion inhibitor for steel in sulphuric acid medium

The corrosion behavior of mild steel in sulphuric acid solution containing various concentrations of a co-polymer formed between maleic anhydride and N-vinyl-2-pyrrolidone (VPMA) was investigated using weight-loss, polarization and electrochemical impedance techniques. The polymer acts as an effective corrosion inhibitor for steel in sulphuric acid medium. The inhibition process is attributed to the formation of an adsorbed film of co-polymer on the metal surface which protects the metal against corrosion. Scanning electron microscopy (SEM) studies of the metal surfaces confirmed the existence of an adsorbed film. The adsorption followed the Langmuir isotherm. The protection efficiency increased with increase in inhibitor concentration and decreased with increase in temperature and acid concentration. The thermodynamic functions of the adsorption and dissolution processes were evaluated.     

Experimental and computational studies of naphthyridine derivatives as corrosion inhibitor for N80 steel in 15% hydrochloric acid

The inhibition effect of three naphthyridine derivatives namely 2-amino-4-(4-methoxyphenyl)-1,8-naphthyridine-3-carbonitrile (ANC-1), 2-amino-4-(4-methylphenyl)-1,8-naphthyridine-3-carbonitrile (ANC-2) and 2-amino-4-(3-nitrophenyl)-1,8-naphthyridine-3-carbonitrile (ANC-3) as corrosion inhibitors for N80 steel in 15% HCl by using gravimetric, electrochemical techniques (EIS and potentiodynamic polarization), SEM, EDX and quantum chemical calculation. The order of inhibition efficiency is ANC-1>ANC-2>ANC-3. Potentiodynamic polarization reveals that these inhibitors are mixed type with predominant cathodic control. Studied inhibitors obey the Langmuir adsorption isotherm. The quantum calculation is in good agreement with experimental results.     

Experimental and theoretical study for corrosion inhibition of mild steel in hydrochloric acid solution by some new hydrazine carbodithioic acid derivatives

The corrosion inhibition of mild steel in 0.5 M hydrochloric acid solutions by some new hydrazine carbodithioic acid derivatives namely N′-furan-2-yl-methylene-hydrazine carbodithioic acid (A), N′-(4-dimethylamino-benzylidene)-hydrazine carbodithioic acid (B) and N′-(3-nitro-benzylidene)-hydrazine carbodithioic (C) was studied using chemical (weight loss) and electrochemical (potentiodynamic and electrochemical impedance spectroscopy, EIS) measurements. These measurements show that the inhibition efficiency obtained by these compounds increased by increasing their concentration. The inhibition efficiency follow the order C > B > A. Polarization studies show that these compounds act as mixed type inhibitors in 0.5 M HCl solutions. These inhibitors function through adsorption following Langmuir isotherm. The electronic properties of these inhibitors, obtained using PM3 semi-empirical self-consistence field method, have been correlated with their experimental efficiencies using non-linear regression method.     

Density functional theory and molecular dynamics simulation study on corrosion inhibition performance of mild steel by mercapto-quinoline Schiff base corrosion inhibitor

Corrosion inhibition mechanism of two mercapto-quinoline Schiff bases, eg., 3-((phenylimino)methyl)quinoline-2-thiol (PMQ) and 3-((5-methylthiazol-2-ylimino)methyl) quinoline-2-thiol (MMQT) on mild steel surface is investigated by quantum chemical calculation and molecular dynamics simulation. Quantum chemical parameters such as E_HOMO, E_LUMO, energy gap (ΔE), dipolemoment (µ), electronegativity (χ), global hardness (η) and fraction of electron transfers from the inhibitor molecule to the metallic atom surface (ΔN) have been studied to investigate their relative corrosion inhibition performance. Parameters like local reactive sites of the present molecule have been analyzed through Fukui indices. Moreover, adsorption behavior of the inhibitor molecules on Fe (1 1 0) surface have been analyzed using molecular dynamics simulation. The binding strength of the concerned inhibitor molecules on mild steel surface follows the order MMQT>PMQ, which is in good agreement with the experimentally determined inhibition efficiencies. In view of the above, our approach will be helpful for quick prediction of a potential inhibitor from a lot of similar inhibitors and subsequently in their rational designed synthesis for corrosion inhibition application following a wet chemical synthetic route.     

An electrochemical study for corrosion inhibition of iron by some organic phosphonium chloride derivatives in acid media

The inhibiting action of (chloromethyl) triphenyl phosphonium chloride (CTP), tetraphenyl phosphonum chloride (TP), triphenyl phosphine oxide (TPO), triphenyl (phenylmethyl) phosphonium chloride (TPM) and triphenyl phosphine (TPP) on the corrosion of iron in 1 M HCl solution was studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Experimental results revealed that CTP, TP, TPO, and TPM act as inhibitors for iron in acid environments, while TPP is an accelerator. These compounds are mixed-type inhibitors and the inhibition efficiency increased with increasing concentrations. Equivalent circuits of the investigated systems are suggested.     

Corrosion inhibition of steel in sulphuric acid by pyrrolidine derivatives

Novel corrosion inhibitors, namely 1-{2-[(2-hydroxyethyl)thio]ethyl}pyrrolidin-2-one (P5) and {[2-(2-oxopyrrolidin-1-yl)ethyl]thio}acetic acid (P4), were synthesised and tested as corrosion inhibitors for steel in 0.5 M H₂SO₄. The effects of P4 and P5 are also compared to their initial reactants 1-vinylpyrrolidin-2-one (P1), 2-mercaptoethanol (P2) and mercaptoacetic acid (P3). The study was carried out by weight loss measurements, potentiodynamic polarisation, linear polarisation resistance (R_p) and electrochemical impedance spectroscopy (EIS) methods. The inhibition efficiency increases with the concentration of P5 to attain 89% at 5 × 10⁻³ M. We note good agreement between the various methods explored. Polarisation measurements show also that the pyrrolidones act essentially as cathodic inhibitors. The cathodic curves indicate that the reduction of proton at the steel surface is an activating mechanism. P4 and P5 adsorb on the steel surface according to Langmuir adsorption model. Effect of temperature is also studied in the 298-353 K range. Efficiency is explained by the theoretical studies.     

Density Functional Theory (DFT) modeling and Monte Carlo simulation assessment of inhibition performance of some carbohydrazide Schiff bases for steel corrosion

DFT and Monte Carlo simulation were performed on three Schiff bases namely, 4-(4-bromophenyl)-N^′-(4-methoxybenzylidene)thiazole-2-carbohydrazide (BMTC), 4-(4-bromophenyl)-N^′-(2,4-dimethoxybenzylidene)thiazole-2-carbohydrazide (BDTC), 4-(4-bromophenyl)-N^′-(4-hydroxybenzylidene)thiazole-2-carbohydrazide (BHTC) recently studied as corrosion inhibitor for steel in acid medium. Electronic parameters relevant to their inhibition activity such as E_HOMO, E_LUMO, Energy gap (ΔE), hardness (η), softness ($\sigma$), the absolute electronegativity (χ), proton affinity $\left(\mathrm{PA}\right)$ and nucleophilicity (ω) etc., were computed and discussed. Monte Carlo simulations were applied to search for the most stable configuration and adsorption energies for the interaction of the inhibitors with Fe (110) surface. The theoretical data obtained are in most cases in agreement with experimental results.     

Effect of surface nanocrystallization induced by fast multiple rotation rolling on hardness and corrosion behavior of 316L stainless steel

A nanostructured layer was fabricated by using fast multiple rotation rolling (FMRR) on the surface of 316L stainless steel. The microstructure in the surface was characterized by transmission electron microscopy and X-ray diffraction. The effects of FMRR on the microhardness, surface roughness and corrosion behavior of the stainless steel were investigated by microhardness measurements, surface roughness measurements, potentiodynamic polarization curves and pitting corrosion tests. The surface morphologies of pitting corrosion specimens were characterized by scanning electron microscopy. The results show that FMRR can cause surface nanocrystallization with the grain size ranges from 6 to 24 nm in the top surface layer of the sample. The microhardness of FMRR specimen in the top surface layer remarkably increases from 190 to 530 HV. However, the surface roughness slightly rises after FMRR treatment. The potentiodynamic polarization curves and pitting corrosion tests indicated that the FMRR treated 316L stainless steel with a surface nanocrystallized layer reduced the corrosion resistance in a 3.5% NaCl solution and enhanced the pitting corrosion rate in a FeCl₃ solution. Possible reasons leading to the decrease in corrosion resistance were discussed.     

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通过失重法结合SEM、金相分析等手段,研究了含焊缝的316L不锈钢试样在350°C、0.15MPa液态锂中500h的静态腐蚀,并采用LIBS结合台阶仪表征液态锂的渗入深度。结果表明,锂对含焊缝的316L不锈钢样式的平均腐蚀速率为99.8mg·m?2·h?1;腐蚀深度为6.4μm;渗入深度在316L不锈钢焊缝处为8.6μm,在母材处为4.8μm。在焊缝处锂对材料有明显的晶间腐蚀。     

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利用脉冲激光诱导击穿光谱仪(LIBS)结合SEM、EDX和维氏硬度(HV)等分析手段,分析了316L不锈钢在350℃的液态锂中静态腐蚀500h后的腐蚀特性.微观形貌分析表明:样品存在较明显的晶间腐蚀,其腐蚀层厚度约为2.7μm.硬度分析表明:腐蚀后表面硬度值约HV234.72,约是腐蚀前硬度值的0.78倍.LIBS组分分析表明:经液态锂腐蚀后的样品表面Ni、Cr等元素含量相对减少;在被腐蚀区域Li元素含量随激光击打深度的增加而减少,而Ni、Cr等元素含量与之近似呈成正比递增;母材区Li元素的渗透深度约3.5μm,约是焊缝区的0.6倍.     

Electrophoretic deposition of PVA coated hydroxyapatite on 316L stainless steel

Polyvinyl alcohol (PVA) coated hydroxyapatite was deposited onto a 316L stainless steel substrate by electrophoretic deposition. Deposition was carried out in a methanol suspension at pH 5.5 using a graphite rod as an anode. Parameters such as PVA concentration, deposition voltage and time were optimized to achieve a homogeneous, crack-free adhesive coating. Techniques such as X-ray diffraction and Fourier transform infrared spectroscopy were used to study the phase composition of the coated materials and the stability of hydroxyapatite in the presence of PVA.     

Pyridine–pyrazole compound as inhibitor for steel in 1 M HCl

The influence of 3,5-dimethyl-1H-pyrazole (P1), pyridine (P2) and 2-(3-methyl-1H-pyrazol-5-yl) pyridine (P3) on the corrosion inhibition of steel in molar hydrochloric acid solution is studied using weight-loss, potentiodynamic and EIS measurements. Results obtained shows that P3 is the best inhibitor and its inhibition efficiency increases with the increase of concentration to attain 89% since 10⁻³ M. Potentiodynamic polarisation studies clearly reveal that it acts essentially as a cathodic inhibitor. The inhibitor studied reduces the corrosion rates. E (%) values obtained from various methods used are in good agreement. Adsorption of P3 on steel surface has an S-shaped adsorption isotherm.     

The inhibitive effect of bipyrazolic derivatives on the corrosion of steel in hydrochloric acid solution

The effect of two pyrazole-type organic compounds, namely ethyl 5,5′-dimethyl-1′H-1,3′-bipyrazole-3 carboxylate (P1) and 3,5,5′-trimethyl-1′H-1,3′-bipyrazole (P2) on the corrosion behaviour of steel in 1 M hydrochloric acid (HCl) solution is investigated at 308 K by weight loss measurements, potentiodynamic polarisation and impedance spectroscopy (EIS) methods. The inhibition efficiencies obtained from cathodic Tafel plots, gravimetric and EIS methods are in good agreement. Results obtained show that the compound P2 is the best inhibitor and its efficiency reaches 84% at 10⁻³ M. Potentiodynamic polarisation studies show that pyrazolic derivatives are cathodic-type inhibitors and these compounds act on the cathodic reaction without changing the mechanism of the hydrogen evolution reaction. The inhibition efficiency of P2 is temperature-dependent in the range from 308 to 353 K and the associated activation energy has been determined. P2 adsorbs on the steel surface according to Langmuir adsorption model. The calculation of the total partial charge of inhibitor atoms is computed.     

液态金属锂对于316L不锈钢焊接件的腐蚀行为研究

通过失重法结合SEM、金相分析等手段,研究了含焊缝的316L 不锈钢试样在350°C、0.15MPa 液态锂中500h 的静态腐蚀,并采用LIBS 结合台阶仪表征液态锂的渗入深度。结果表明,锂对含焊缝的316L 不锈钢样式的平均腐蚀速率为99.8mg·m^-2·h^-1;腐蚀深度为6.4μm;渗入深度在316L 不锈钢焊缝处为8.6μm,在母材处为4.8μm。在焊缝处锂对材料有明显的晶间腐蚀。     

316L不锈钢在静态液态锂中的腐蚀行为研究

利用脉冲激光诱导击穿光谱仪(LIBS)结合SEM、EDX和维氏硬度(HV)等分析手段,分析了316L不锈钢在350℃的液态锂中静态腐蚀500h后的腐蚀特性。微观形貌分析表明：样品存在较明显的晶间腐蚀,其腐蚀层厚度约为2.7μm。硬度分析表明：腐蚀后表面硬度值约HV234.72,约是腐蚀前硬度值的0.78倍。LIBS组分分析表明：经液态锂腐蚀后的样品表面Ni、Cr等元素含量相对减少;在被腐蚀区域Li元素含量随激光击打深度的增加而减少,而Ni、Cr等元素含量与之近似呈成正比递增;母材区Li元素的渗透深度约3.5μm,约是焊缝区的0.6倍。     

Inhibition of mild steel corrosion by Morinda tinctoria leaves extract in sulphuric acid medium

The corrosion inhibition of mild steel in 0.5 M sulphuric acid by aqueous and acid extracts of leaves of Morinda tinctoria was studied using weight loss, colorimetric and electrochemical techniques. Results obtained indicate that both the extracts are effective in sulphuric acid medium and the efficiency decreases with increase in temperature. Added halide additives improve the efficiency of the inhibitor. From the thermodynamic, spectral, and surface analyses, the nature of adsorption has been found out.     

Investigation of the inhibitive effect of triphenyltin 2-thiophene carboxylate on corrosion of steel in 2 M H3PO4 solutions

A new organic compound was synthesised and tested as corrosion inhibitor of steel in phosphoric acid medium using gravimetric, electrochemical polarisation and electrochemical impedance spectroscopy (EIS) measurements. Results obtained show that the inhibitor studied is a good cathodic inhibitor. EIS results show that the change in the impedance parameters (R_T and C_dl) with concentration of triphenyltin 2-thiophene carboxylate (TTC) is indicative of the adsorption of molecules leading to the formation of a protective layer on the surface of steel. The effect of the temperature on the steel corrosion in 2 M H₃PO₄ and with addition of various concentrations of TTC in the range of temperature 298-348 K was studied. The associated apparent activation corrosion energy has been determined.     

1,3-Bis(3-hyroxymethyl-5-methyl-1-pyrazole) propane as corrosion inhibitor for steel in 0.5 M H2SO4 solution

The effect of addition of 1,3-bis(3-hyroxymethyl-5-methyl-1-pyrazole) propane (M = 264 g). HMPP on steel corrosion in 0.5 M sulphuric acid is studied by weight-loss, electrochemical polarisation and electrochemical impedance spectroscopy (EIS) measurements at various temperatures. The results obtained showed that HMPP acts as a good corrosion inhibitor. The inhibition efficiency increases with the bipyrazole compound to attain 88%. It acts as a mixed-type inhibitor. Trends in the increase of charge-transfer resistance and decrease of capacitance values also show the adsorption of the molecule on the metal surface. The bipyrazole adsorbs on the steel surface according to the Langmuir isotherm adsorption model. Effect of temperature indicates that inhibition efficiency decreases with temperature between 25 and 85 °C.     

Inhibiting effects of some oxadiazole derivatives on the corrosion of mild steel in perchloric acid solution

The efficiency of 3,5-bis(n-pyridyl)-1,3,4-oxadiazole (n-POX, n = 1, 2, 3), as corrosion inhibitors for mild steel in 1 M perchloric acid (HClO₄) have been determined by weight loss measurements and electrochemical studies. The results show that these inhibitors revealed a good corrosion inhibition even at very low concentrations. Comparison of results among those obtained by the studied oxadiazoles shows that 3-POX was the best inhibitor. Polarisation curves indicate that n-pyridyl substituted-1,3,4-oxadiazoles are mixed type inhibitors in 1 M HClO₄. The adsorption of these inhibitors follows a Langmuir isotherm model. The electronic properties of n-POX, obtained using the AM1 semi-empirical quantum chemical approach, were correlated with their experimental efficiencies using the linear resistance model (LR).