Effect of cerium ions on corrosion inhibition of PANI for iron in 0.5 M H2SO4

In recent years conducting polymers such as polyaniline are used as corrosion inhibitors for metals in acids. The performance of the inhibitor can be enhanced either by the addition of halide ions or metal cations. A study has been made on the effect of addition of ceric ions on the corrosion inhibition performance of polyaniline for iron in 0.5 M H₂SO₄. Techniques such as electrochemical impedance spectroscopy, potentiodynamic polarization and linear polarization resistance methods have been employed to study the corrosion inhibition. The polyaniline has been used in the concentration range of 10-100 ppm and the ceric ions concentration has been maintained at 1 × 10⁻³ M. The inhibition efficiency of polyaniline at 10 ppm has been increased from 53 to 88% and for 50 ppm from 71 to 90% in the presence of ceric ions. The enhanced inhibition of polyaniline in presence of ceric ions is due to the higher coverage of polyaniline-cerium complex.     

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.     

Inhibition of steel corrosion in 2 M H3PO4 by artemisia oil

Artemisia oil (Ar) is extracted from artemisia herba alba collected in Ain es-sefra-Algeria, and tested as corrosion inhibitor of steel in 2 M H₃PO₄ using weight loss measurements, electrochemical polarisation and EIS methods. The naturally oil reduces the corrosion rate. The inhibition efficiency was found to increase with oil content to attain 79% at 6 g/l. Ar acts as a cathodic inhibitor. The effect of temperature on the corrosion behaviour of steel indicates that inhibition efficiency of the natural substance decreases with the rise of temperature. The adsorption isotherm of natural product on the steel has been determined.     

Corrosion inhibition of steel in 0.5 M H2SO4 by [(2-pyridin-4-ylethyl)thio]acetic acid

The influence of [(2-pyridin-4-ylethyl)thio]acetic acid (P1) and pyridine (P2) on the corrosion inhibition of steel in sulphuric acid solution is studied using weight loss, potentiodynamic polarisation and linear polarisation resistance (R_p) and electrochemical impedance spectroscopy (EIS) measurements. Results obtained show that P1 is the best inhibitor and its inhibition efficiency (E%) increases with the increase of concentration. The highest E% of 82% is observed at 5 × 10⁻³ M. Potentiodynamic polarisation studies clearly reveal that P1 acts as a mixed inhibitor. The inhibitor studied reduces the corrosion rates. E% values obtained from various methods used are in good agreement. Adsorption of P1 on steel surface obeys to Langmuir adsorption isotherm. Effect of temperature indicates that E% decreases with temperature between 298 and 353 K.     

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.     

Effect of copper ions implantation on corrosion behavior of zircaloy-4 in 1 M H2SO4

In order to study the effect of copper ion implantation on the aqueous corrosion behavior, samples of zircaloy-4 were implanted with copper ions with fluences ranging from 1 × 10¹⁶ to 1 × 10¹⁷ ions/cm², using a metal vapor vacuum arc source (MEVVA) operated at an extraction voltage of 40 kV. The valence states and depth distributions of elements in the surface layer of the samples were analyzed by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), respectively. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase transformation due to the copper ion implantation. The potentiodynamic polarization technique was employed to evaluate the aqueous corrosion resistance of implanted zircaloy-4 in a 1 M H₂SO₄ solution. It was found that a significant improvement was achieved in the aqueous corrosion resistance of zircaloy-4 implanted with copper ions when the fluence is smaller than 5 × 10¹⁶ ions/cm². The corrosion resistance of implanted samples declined with increasing the fluence. Finally, the mechanism of the corrosion behavior of copper-implanted zircaloy-4 was discussed.     

Influence of titanium ions implantation on corrosion behavior of zirconium in 1 M H2SO4

In order to study the effect of titanium ion implantation on the aqueous corrosion behavior of zirconium, specimens were implanted with titanium ions with fluence ranging from 1 × 10¹⁶ to 1 × 10¹⁷ ions/cm², using a metal vapor vacuum arc (MEVVA) source at an extraction voltage of 40 kV. The valence states and depth distributions of elements in the surface layer of the samples were analyzed by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), respectively. The potentiodynamic polarization technique was employed to evaluate the aqueous corrosion resistance of implanted zirconium in a 1 M H₂SO₄ solution. It was found that a significant improvement was achieved in the aqueous corrosion resistance of zirconium implanted with titanium ions. The larger the fluence, the better is the corrosion resistance of implanted sample. Finally, the mechanism of the corrosion behavior of titanium-implanted zirconium was discussed.     

Effect of the heat treatment on the corrosion behaviour of amorphous Fe-Cr-P-C-Si alloy in 0.5 M H2SO4

The effect of the heat treatment on the corrosion behaviour of amorphous Fe₈₅Cr₅P₆C₃Si alloy in 0.5 M H₂SO₄ has been investigated using electrochemical techniques. Heat treatment was carried out at temperatures varying between 250 and 650 °C at different times 30, 60, 120 and 240 min. The evolution of crystallization processes after annealing was identified by differential thermal analysis (DTA) and by X-ray diffraction (XRD). The diagrams obtained by DTA show that the structure of samples treated at high temperature changes towards a crystalline state. This crystallization phenomenon is confirmed by the analysis with the XRD. The results obtained from the polarization curves reveal that for all the studied temperatures of annealing, Fe-Cr-P-C-Si exhibits a phenomenon of passivation without breakdown of passivity. The best corrosion resistance is obtained at the temperature of annealing 350 °C. For an annealing at higher temperatures, Fe₈₅Cr₅P₆C₃Si becomes less corrosion resistant than same amorphous alloy treated with temperatures lower than 350 °C.     

Synergistic effect between 4-(2-pyridylazo) resorcin and chloride ion on the corrosion of cold rolled steel in 0.5 M sulfuric acid

The corrosion inhibition of 1-(2-pyridylazo)-2-naphthol (PAR) on the corrosion of cold rolled steel in 0.5 M sulfuric acid (H₂SO₄) was studied using weight loss method and potentiodynamic polarization method. Results obtained revealed that together with chloride ion, PAR is an effective corrosion inhibitor for steel corrosion in sulfuric acid. It was found that for steel corrosion inhibition in the presence of single PAR in sulfuric acid the Temkin adsorption isotherm may be used to explain the adsorption phenomenon. For the mixture of PAR and NaCl used as corrosion inhibitor, however, the Langmuir adsorption isotherm can be used to satisfactorily elucidate the adsorption of mixture of PAR and NaCl. Potentiodynamic polarization studies showed that single PAR mainly acts as a cathodic inhibitor for the corrosion of steel in 0.5 M sulfuric acid. The mixture of PAR and chloride ion, however, acts as a mixed type inhibitor that mainly inhibits cathodic reaction of the steel corrosion in sulfuric acid. By means of electrochemical polarization tests, a desorption potential at ca. −370 mV was observed for the adsorption of mixture of PAR and chloride ion, when potential reaches this value, adsorbed inhibitor molecule heavily departs from the steel surface. For the mixture of PAR and chloride ion, thermodynamic parameters such as adsorption heat, adsorption entropy and adsorption free energy were obtained from experimental data of the temperature studies of the inhibition process at four temperatures ranging from 30 to 45 °C, the kinetic data such as apparent activation energies and pre-exponential factors at different concentrations of the inhibitor were calculated, and the effect of the apparent activation energies and pre-exponential factors on the corrosion rates of cold rolled steel was discussed. The most suitable range of inhibitor concentration was discussed. The inhibitive action was satisfactorily explained by using both thermodynamic and kinetic models. Synergism between chloride ion and PAR was proposed. The results obtained from weight loss and potentiodynamic polarization were in good agreement.     

Inhibition of iron corrosion in 0.5 M sulphuric acid by metal cations

Corrosion inhibitors are widely used in acid solutions during pickling and descaling. Mostly organic compounds containing N, O, and S groups are employed as inhibitors. In this study, the inhibition performance of metal cations such as Zn²⁺, Mn²⁺ and Ce⁴⁺ ions in the concentration range 1-10 × 10⁻³ M has been found out. The corrosion behaviour of iron in 0.5 M H₂SO₄ in the presence of metal cations is studied using polarization and impedance methods. It is found that the addition of these metal cations inhibits the corrosion markedly. The inhibition effect is in the following order Ce⁴⁺ ? Mn²⁺ > Zn²⁺.     

The corrosion inhibition and gas evolution studies of some surfactants and citric acid on lead alloy in 12.5 M H2SO4 solution

The inhibition action of the citric acid and three surfactants: sodium dodecyl sulfate (SDS), t-octyl phenoxy polyethoxyethanol (Triton X-100), sodium dodecyl benzene sulphonate (SDBS) on the corrosion behavior and gas evolution of Pb-Sb-As-Se was investigated in 12.5 M H₂SO₄ solution with linear sweep polarization, cyclic voltammetry and weight loss measurements methods. The results drawn from different techniques are comparable. It was found that these surfactants and citric acid act as good inhibitors for the corrosion of lead alloy in H₂SO₄ solution. SDS inhibited most effectively the lead alloy corrosion among the three surfactants and citric acid. The inhibition efficiency for the inhibitors decreases in the order: SDS > SDBS > Triton X-100 > citric acid > blank. The inhibition efficiency increases with rising of the inhibitor concentration. In this work, the effect of the inhibitors on hydrogen and oxygen evolution was studied. In addition, it was found that the adsorption of used inhibitors on lead alloy surface follows Langmuir isotherm.     

Establishment of equivalent circuits from electrochemical impedance spectroscopy study of corrosion inhibition of steel by pyrazine in sulphuric acidic solution

This paper describes the use of the electrochemical impedance spectroscopy technique (EIS) in order to study the corrosion inhibition process of steel in 0.5 M H₂SO₄ solution at the open circuit potential (OCP). Diethyl pyrazine-2,3-dicarboxylate (Prz) as a non-ionic surfactant (NS) inhibitor has been examined. The Nyquist diagrams consisted of a capacitive semicircle at high frequencies followed by a well-defined inductive loop at low frequency values. The impedance measurements were interpreted according to suitable equivalent circuits. The results obtained showed that the Prz is a good inhibitor. The inhibition efficiency increases with an increase in the surfactant concentration to attain 80% at the 5 × 10⁻³M. Prz is adsorbed on the steel surface according to a Langmuir isotherm adsorption model.     

A novel electrodeposited Cu-Zn-Bi film with increased corrosion resistance in a 0.05 M K2SO4 solution

A single phase Cu-Zn-Bi film is fabricated on the steel wire by electrodeposition. Bi addition (∼1 wt.%) greatly increases the corrosion resistance of brass (Cu−36 wt.% Zn) film in a 0.05 M K₂SO₄ solution as shown by potentiodynamic polarization and electrochemical impendence spectroscopy (EIS) experiments. It is proposed that the main reason for the improvement in the corrosion resistance by the Bi addition is that it greatly increased the crack resistance, which thus prevents crack-induced galvanic corrosion occurring between the brass film and the steel substrate.     

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.     

Berberine as a natural source inhibitor for mild steel in 1 M H2SO4

Berberine was abstracted from coptis chinensis and its inhibition efficiency on corrosion of mild steel in 1 M H₂SO₄ was investigated through weight loss experiment, electrochemical techniques and scanning electronic microscope (SEM) with energy disperse spectrometer (EDS). The weight loss results showed that berberine is an excellent corrosion inhibitor for mild steel immersed in 1 M H₂SO₄. Potentiodynamic curves suggested that berberine suppressed both cathodic and anodic processes for its concentrations higher than 1.0 × 10⁻⁴ M and mainly cathodic reaction was suppressed for lower concentrations. The Nyquist diagrams of impedance for mild steel in 1 M H₂SO₄ containing berberine with different concentrations showed one capacitive loop, and the polarization resistance increased with the inhibitor concentration rising. A good fit to Flory-Huggins isotherm was obtained between surface coverage degree and inhibitor concentration. The surface morphology and EDS analysis for mild steel specimens in sulfuric acid in the absence and presence of the inhibitor also proved the results obtained by the weight loss and electrochemical experiments. The correlation of inhibition effect and molecular structure of berberine was then discussed by quantum chemistry study.     

Synergistic effect between 4-(2-pyridylazo) resorcin and chloride ion on the corrosion of cold rolled steel in 1.0 M phosphoric acid

The synergistic inhibition between 4-(2-pyridylazo) resorcin (PAR) and chloride ion on the corrosion of cold rolled steel in 1.0 M phosphoric acid was studied using weight loss and potentiodynamic polarization method. Results obtained revealed that single PAR is not an effective inhibitor for steel corrosion in phosphoric acid, but in the presence of chloride ion, PAR may act as a good inhibitor due to the synergism. It is found that the adsorption of PAR accords with the Langmuir adsorption isotherm in the absence and presence of chloride ion. Potentiodynamic polarization studies show that PAR is an anodic inhibitor for steel in 1.0 M phosphoric acid, and with addition of chloride ion PAR acts as a mixed type inhibitor. The experimental temperature ranges from 30 to 45 °C. The kinetic data such as apparent activation energies and pre-exponential factors at different concentrations of the inhibitor were calculated, and the effect of the apparent activation energies and pre-exponential factors on the corrosion rates of cold rolled steel was discussed. The inhibitive action was satisfactorily explained by using kinetic models.     

Synergistic upconversion effect in NaYF4:Yb,Tm nanorods under dual excitation of 980 nm and 808 nm

NaYF₄:Yb³⁺,Tm³⁺ nanorods are prepared with hydrothermal method. The upconversion luminescent properties are investigated under dual excitation of 980 nm and 808 nm. The blue emission is observed at about 475 nm under dual excitation. The intensity is 2.6 times higher than the total intensity of the two corresponding single wavelength excitations, showing a synergistic upconversion effect occurring there. The dual wavelength excitation not only effectively decreases non-radiative relaxation pumped by 980 nm but also reduces the rate of the back energy transfer from Tm³⁺ to Yb³⁺ pumped by 808 nm. The result provides a possible new way to further improve the upconversion efficiency of rare earth doped phosphor.     

Inhibition of aluminum corrosion by phthalazinone and synergistic effect of halide ion in 1.0 M HCl

The inhibitive effects of 1-(2H)-phthalazinone (PTO) for aluminum alloy (2024) corrosion in 1.0 M HCl solution and the synergistic effect of KI on the corrosion inhibition efficiency were assessed using electrochemical measurements. Results showed that the inhibition efficiency increased with an increase in concentration of the PTO and synergistically increased with addition of KI. Adsorption characteristic of PTO molecules in absence and presence of KI was approximated by Freundlich and Langmuir adsorption isotherm models, respectively. The synergistic effect is found to decrease with increase in the concentration of PTO and a competitive inhibition mechanism exists between KI and PTO cations.     

Role of chromium ion implantation on the corrosion behavior of zirconium in 1N H2SO4

In order to study the effect of chromium ion implantation on the aqueous corrosion behavior of zirconium, specimens were implanted by chromium ions with a dose range from 1×10¹⁶ to 1×10¹⁷ ions/cm², using MEVVA source at an extracted voltage of 40 kV. The valence and elements penetration distribution of the surface layer were analyzed by X-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES), respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the micro-morphology and microstructure of chromium-implanted samples. The potentiodynamic polarization measurement was employed to value the aqueous corrosion resistance of zirconium in a 1N H₂SO₄ solution. It was found that a significant improvement was achieved in the aqueous corrosion resistance of zirconium compared with that of as-received zirconium. The mechanism of the corrosion resistance improvement of chromium-implanted zirconium is probably due to the addition of the chromium oxide dispersoid into the zirconium matrix.     

Inhibitive action of indole-5-carboxylic acid towards corrosion of mild steel in deaerated 0.5 M sulfuric acid solutions

Inhibition of mild steel corrosion in deaerated 0.5 M sulfuric acid solutions containing various concentrations of indole-5-carboxylic acid is studied in the temperature range from 25 to 55 °C using weight-loss, potentiodynamic and spectrophotometric tests. The adsorptive behaviour of inhibitor is also investigated using electrochemical impedance spectroscopy measurements. The indole-5-carboxylic acid is found to shift the corrosion potentials towards more noble values. This shift indicates that the addition of inhibitor mainly affects the anodic process, raising the anodic overpotential more than that of the cathodic, i.e. the indole-5-carboxylic acid behaves as mixed-type inhibitor. Because the cathodic Tafel slopes for hydrogen reduction (b_c) are affected, the inhibitor probably affects the hydrogen reduction mechanism. The activation energy values (E_a) indicate that the indole-5-carboxylic acid increases the activation energy of the corrosion reaction. The adsorption behaviour of indole-5-carboxylic acid follows Langmuir's isotherm. Both the low values of and its decrease with temperature suggest physical adsorption. Double layer capacitance-potential curves indicate considerable adsorption of the inhibitor in the potential range (−400 to −800 mV/_SCE).