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.     

In vitro corrosion and biocompatibility study of phytic acid modified WE43 magnesium alloy

Phytic acid (PA) conversion coating on WE43 magnesium alloy was prepared by the method of immersion. The influences of phytic acid solution with different pH on the microstructure, properties of the conversion coating and the corrosion resistance were investigated by SEM, FTIR and potentiodynamic polarization method. Furthermore, the biocompatibility of different pH phytic acid solution modified WE43 magnesium alloys was evaluated by MTT and hemolysis test. The results show that PA can enhance the corrosion resistance of WE43 magnesium especially when the pH value of modified solution is 5 and the cytotoxicity of the PA coated WE43 magnesium alloy is much better than that of the bare WE43 magnesium alloy. Moreover, all the hemolysis rates of the PA coated WE43 Mg alloy were lower than 5%, indicating that the modified Mg alloy met the hemolysis standard of biomaterials. Therefore, PA coating is a good candidate to improve the biocompatibility of WE43 magnesium alloy.     

Influence of poly(aminoquinone) on corrosion inhibition of iron in acid media

The inhibitor performance of chemically synthesized water soluble poly(aminoquinone) (PAQ) on iron corrosion in 0.5 M sulphuric acid was studied in relation to inhibitor concentration using potentiodynamic polarization and electrochemical impedance spectroscopy measurements. On comparing the inhibition performance of PAQ with that of the monomer o-phenylenediamine (OPD), the OPD gave an efficiency of 80% for 1000 ppm while it was 90% for 100 ppm of PAQ. PAQ was found to be a mixed inhibitor. Besides, PAQ was able to improve the passivation tendency of iron in 0.5 M H₂SO₄ markedly.     

Ultrasonic irradiation and its application for improving the corrosion resistance of phosphate coatings on aluminum alloys

In this paper, ultrasonic irradiation was utilized for improving the corrosion resistance of phosphate coatings on aluminum alloys. The chemical composition and morphology of the coatings were analyzed by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The effect of ultrasonic irradiation on the corrosion resistance of phosphate coatings was investigated by polarization curves and electrochemical impedance spectroscopy (EIS). Various effects of the addition of Nd₂O₃ in phosphating bath on the performance of the coatings were also investigated. Results show that the composition of phosphate coating were Zn₃(PO₄)₂ · 4H₂O(hopeite) and Zn crystals. The phosphate coatings became denser with fewer microscopic holes by utilizing ultrasonic irradiation treatment. The addition of Nd₂O₃ reduced the crystallinity of the coatings, with the additional result that the crystallites were increasingly nubby and spherical. The corrosion resistance of the coatings was also significantly improved by ultrasonic irradiation treatment; both the anodic and cathodic processes of corrosion taking place on the aluminum alloy substrate were suppressed consequently. In addition, the electrochemical impedance of the coatings was also increased by utilizing ultrasonic irradiation treatment compared with traditional treatment.     

Synergistic effect of silver seeds and organic modifiers on the morphology evolution mechanism of silver nanoparticles

Triangular, truncated triangular, quadrangular, hexagonal, and net-structured silver nanoplates as well as decahedral silver nanoparticles were manipulatively prepared starting from silver nitrate and silver seeds in the presence of poly(ethylene glycol) (PEG), poly(N-vinyl pyrrolidone) (PVP), and Tween 80 at room temperature, respectively. UV-vis spectroscopy, XRD, HRTEM, SAED, and FTIR were used to illustrate the crystal growth process and to characterize the resultant silver nanoparticles. It was found that the silver seeds and organic modifiers synergistically affected the morphology evolution of the silver nanoparticles. The co-presence of silver seeds and PEG was beneficial to the formation of triangular and truncated triangular silver nanoplates; the silver seeds and PVP favored the formation of polygonal silver nanoplates; the silver seeds and Tween 80 preferred to the formation of net-structured silver plates. The morphology evolution of the resultant silver nanoparticles was correlated with the crystallinity of the silver seeds and the adsorption ability of the organic modifiers on the crystal surfaces.     

Analysis of refractometric fiber optic state-of-charge (SOC) monitoring sensor for lead acid battery

In situ monitoring of the state of charge (SOC) of lead acid battery is important to understand the residual electrical energy. Usage of battery reduces the charge content of the active electrolyte which in turn changes its refractive index. This paper reports refractometric fiber optic sensor developed for on-line monitoring of SOC. The SOC is monitored during discharging phases of the battery using the developed fiber optic sensor probe along with terminal voltage, temperature and depth of discharge using a LABVIEW based data acquisition system. The paper gives the working principle, design and construction details, results and calibration of the fiber optic sensor (FOS) probe. The in situ monitoring capability of the developed FOS is demonstrated in comparison with the contemporary off-line methods of specific gravity and terminal voltage measurements.     

The inhibition effect of some amino acids towards Pb-Sb-Se-As alloy corrosion in sulfuric acid solution

The inhibition effect of three amino acids towards the corrosion of Pb-Sb-Se-As alloy in 1.28 s.g. H₂SO₄ solution was investigated with linear polarization and weight loss measurements methods. The results drawn from two different techniques are comparable. The used amino acids were tryptophane, proline and methionine. The effect of inhibitor concentration and temperature against inhibitor action was investigated. It was found that these inhibitors act as good inhibitors for the corrosion of lead alloy in H₂SO₄ solution. Increasing inhibitor concentration increases the inhibition efficiency. It was found that adsorption of used amino acids on lead alloy surface follows Langmuir isotherm.     

Adsorption orientation of sodium of polyaspartic acid effect on anodic films formed on magnesium alloy

We previously reported organic addition agent in improving the performance of anodic film formed on magnesium alloy. Here we report that the environment-friendly electrolyte with sodium of polyaspartic acid (PASP) affects the anodizing process including the microstructure, phase constituents and corrosion performance. We have used SEM, XRD, XPS and polarization curve to study in detail the electrolyte impact. Our results show that the anodic film in electrolyte with 19.2-28.8 g/L PASP is compact, smooth and high corrosion resistant. And also, increasing the PASP concentration ranging from 9.6 to 28.8 g/L results in enhancing the cell voltage, thickness and the content of compound including MgO and Mg₂SiO₄ in anodic film. Interestingly, the anodic film is non-stoichiometric oxide. Comparing with Tafel curves of the anodic film to the addition of PASP or not to, the corrosion current density is 1-2 magnitudes less than the later. Furthermore, a plausible model we propose that the anodizing process is regulated by two main plausible adsorption orientations of PASP at the surface anode. With the increasing of PASP content, the adsorption orientation may transit from “end-on” to “flat-on”. This research using organic addition agent PASP may further broaden applications of organic additive in the anti-corrosion engineering and electrochemical surface treatment of magnesium alloy.     

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.     

Influence of phytic acid concentration on coating properties obtained by MAO treatment on magnesium alloys

Anodic coatings were prepared by microarc oxidation (MAO) on AZ91HP in a base solution of 10 g/L NaOH with and without the addition of 0-12 g/L phytic acid (C₆H₁₈O₂₄P₆). The influences of C₆H₁₈O₂₄P₆ and its concentration on the conductivity and breakdown voltage were studied. The morphologies and compositions of anodic coatings were determined by environmental scanning electron microscope (ESEM) and energy dispersive X-ray spectroscopy (EDX). Potentiodynamic polarization test was performed in 3.5 wt.% NaCl solution to evaluate the corrosion resistance of anodic coatings. The results showed that with the increase of C₆H₁₈O₂₄P₆ concentration, the solution conductivity decreased while the values of breakdown voltage increased. EDX analysis showed that the coatings formed in solutions with C₆H₁₈O₂₄P₆ addition contained Mg, Al, O, C, P and a trance of Na. The addition of C₆H₁₈O₂₄P₆ into the base solution was helpful in coating formation and the coatings formed in the solution containing 8 g/L C₆H₁₈O₂₄P₆ exhibited the best pore uniformity and corrosion resistance.     

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).     

The corrosion behaviour of polypyrrole coating synthesized in phenylphosphonic acid solution

Electrochemical synthesis of polypyrrole (PPy) film was achieved on mild steel (MS), in monomer containing 0.1 M phenylphosphonic acid solution. The synthesis was carried out using cyclic voltammetry technique. It was found that the electrode surface could only become completely passive, after a few successive cycles in solution of 0.1 M pyrrole + 0.1 M phenylphosphonic acid. Then, the thickness of polymer film was increased with help of successive cycles in a relatively narrower potential range. The corrosion performance of polymer coating was investigated in 3.5% NaCl solution, using electrochemical impedance spectroscopy (EIS) and anodic polarization curves. It was shown that the coating had high stability and low permeability, under such aggressive conditions. The EIS results also showed that the coating exhibited important anodic protection behaviour on mild steel. The percent protection efficiency value (E%) was found to be 98.4% and the percent total porosity value (P%) was determined to be 0.752%, after 96 h exposure time to corrosive solution.     

Synthesis of hollow silver spheres using poly-(styrene-methyl acrylic acid) as templates in the presence of sodium polyacrylate

Hollow silver spheres were successfully prepared by reducing AgNO₃ with ascorbic acid and using negatively charged poly-(styrene-methyl acrylic acid) (PSA) spheres as templates in the presence of sodium polyacrylate as a stabilizer. Firstly, silver cations adsorbed on the surface of PSA spheres via electrostatic attraction between the carboxyl groups and silver cations were reduced in situ by ascorbic acid. The silver nanoparticles deposited on the surface of PSA spheres served as seeds for the further growth of silver shells. After that, extra amount of AgNO₃ and ascorbic acid solutions were added to form PSA/Ag composites with thick silver shells. In order to obtain compact silver shells, the as-prepared PSA/Ag composites were heated at 150 °C for 3 h. Then hollow silver spheres were prepared by dissolving PSA templates with tetrahydrofuran.     

The inhibited effect of some tetrazolic compounds towards the corrosion of brass in nitric acid solution

The effect of the addition of some tetrazolic type organic compounds: 1-phenyl-5-mercapto-1,2,3,4-tetrazole (PMT), 1,2,3,4-tetrazole (TTZ), 5-amino-1,2,3,4-tetrazole (AT) and 1-phenyl-1,2,3,4-tetrazole (PT) on the corrosion of brass in nitric acid is studied by weight loss, polarisation and electrochemical impedance spectroscopy (EIS) measurements. The explored methods gave almost similar results. Results obtained reveal that PMT is the best inhibitor and the inhibition efficiency (E%) follows the sequence: PMT > PT > AT > TTZ. Polarization measurements also indicated that tetrazoles acted as mixed-type inhibitors without changing the mechanism of the hydrogen evolution reaction. Partial π-charge on atoms has been calculated. Correlation between the highest occupied molecular orbital energy E_HOMO and inhibition efficiencies was sought. The adsorption of PMT on the brass surface followed the Langmuir isotherm. Effect of temperature is also studied in the (25-50 °C) range.     

Impacts of oxygen sensitization methods on the deposition and microstructure of ternary lead chalcogenide alloys

Oxygen sensitization and incorporation of ternary lead chalcogenide PbSe_1-xTe_x thin films was investigated with two methods: adding oxygen via PbO to the bulk source alloy and post-deposition oxygen annealing. Characterization of the composition, structure, and morphology of these films confirmed that they follow Vegard's law for lattice parameter, and adding PbO to the source alloy did not impact the lattice parameter. However, adding PbO changed the electrical carrier properties observed in Hall effect measurements without forming any new oxide phase. Conversely, post-deposition annealing increased the lattice parameter due to oxygen incorporation into the lattice via interstitials in samples with appropriate grain boundary orientations. Morphological analysis revealed that PbSe_0.8Te_0.2 films demonstrated (100) texture, while PbSe_0.6Te_0.4 films demonstrated (111) texture with resulting grain boundary orientations more favorable to oxygen diffusion and incorporation. This varying oxygen incorporation from PbO source and oxygen annealing methods reveals trends that can lead to improved photodetector performance.     

Effect of pulse parameters on the passive layer formation on pulse plated Ni-Co alloys

From a chloride bath, Ni-Co alloys were pulse plated by varying the pulse parameters off-time and the peak current densities using a pulse generator that applies a square wave signal in order to examine the mechanism of the passive oxide layer formation on the deposited coatings in the frame of pulse parameters.Cyclic voltammetry and potential step measurements were carried out in order to characterise the electrochemical behaviour on the Ni-Co coatings at a selected electrode potential in an alkaline solution. Calculation of the oxide layer formation was evaluated from the total charge, determined by recorded current-time transients and from ICP-analysis of the samples. The most protective and compact oxide was formed on the sample that was deposited at low current densities and at high off-time.     

Tween-40 as corrosion inhibitor for cold rolled steel in sulphuric acid: Weight loss study, electrochemical characterization, and AFM

The inhibition action of a non-ionic surfactant of tween-40 on the corrosion of cold rolled steel (CRS) in 0.5-7.0 M sulphuric acid (H₂SO₄) was studied by weight loss and potentiodynamic polarization methods. Atomic force microscope (AFM) provided the surface conditions. The inhibition efficiency increases with the tween-40 concentration, while decreases with the sulphuric acid concentration. The adsorption of inhibitor on the cold rolled steel surface obeys the Langmuir adsorption isotherm equation. Effect of immersion time was studied and discussed. The effect of temperature on the corrosion behavior of cold rolled steel was also studied at four temperatures ranging from 30 to 60 °C, the thermodynamic parameters such as adsorption heat, adsorption free energy and adsorption entropy were calculated. A kinetic study of cold rolled steel in uninhibited and inhibited acid was also discussed. The kinetic parameters such as apparent activation energy, pre-exponential factor, rate constant, and reaction constant were calculated for the reactions of corrosion. The inhibition effect is satisfactorily explained by both thermodynamic and kinetic parameters. Polarization curves show that tween-40 is a cathodic-type inhibitor in sulphuric acid. The results obtained from weight loss and potentiodynamic polarization are in good agreement, and the tween-40 inhibition action could also be evidenced by surface AFM images.     

Novel strategy in increasing stability and corrosion resistance for super-hydrophobic coating on aluminum alloy surfaces

A novel super-hydrophobic coating was prepared by chemical modification on the anodized aluminum alloy surface. The surface structure was characterized by water contact angle measurement, scanning electron microscopy (SEM), and the composition was measured by X-ray photoelectron spectroscopy (XPS). The corrosion behavior of the super-hydrophobic coating was evaluated by the polarization curve and the electrochemical impedance spectroscopy (EIS). It was found that the static water contact angle on the surface of super-hydrophobic coating was as high as 167.7 ± 1.2°, and the sliding angle was 5°. The super-hydrophobic coating resulted in excellent corrosion resistance property and the super-hydrophobic coating showed a good stability.     

Mossbauer investigations of corrosion environment influence on Fe valence states in oxide films of zirconium alloys

Mössbauer investigations about iron atom redistribution in oxide films of zirconium alloys subjected to corrosion at 500°C in pure oxygen and water pair have been analysed. The alloys were also subjected to autoclave conditions at a pressure of 10.0 MPa and autoclave conditions at 350°C and at a pressure of 16.8 MPa, using distilled water and water with additives of lithium and fluorine. It is shown that, depending on the corrosion environment, various compounds of iron, such as α-Fe₂O₃, Fe₃O₄, and FeO, as solid solutions of iron in ZrO₂ are formed in oxide films.