pH and iodide ion effect on corrosion inhibition of histidine self-assembled monolayer on copper

Self-assembled monolayer (SAM) of histidine (His) was prepared on copper surface at various pH values. The effect of KI additives on corrosion protection efficiency of His SAM was also studied. The protection abilities of these films against copper corrosion in 0.5 M HCl aqueous solution were investigated using electrochemical impedance spectroscopy and polarization techniques. The results show that the film formed on the electrode is more stable at pH = 10 than that at other pH values. When the iodide ions were added into the His self-assembly solution (pH = 10), protection efficiency was further improved. The inhibition mechanism has been discussed by quantum chemical calculations.     

Self-assembled monolayer of ammonium pyrrolidine dithiocarbamate on copper detected using electrochemical methods, surface enhanced Raman scattering and quantum chemistry calculations

Ammonium pyrrolidine dithiocarbamate (APDTC) monolayer was self-assembled on fresh copper surface obtained after oxidation-reduction cycle treatment in 0.1 mol L^− 1 potassium chloride solution at ambient temperature. The APDTC self-assembled monolayer (SAM) on copper surface was investigated by surface enhanced Raman scattering spectroscopy and the results show that APDTC SAM is chemisorbed on copper surface by its sulfur atoms with perpendicular orientation. The optimum immersing period for SAM formation is 4 h at 0.01 mol L^− 1 concentration of APDTC. The impedance results indicate that APDTC SAM has good corrosion inhibition effects for copper in 0.5 mol L^− 1 hydrochloric acid solution and its maximum inhibition efficiency could reach 95%. Quantum chemical calculations show that APDTC has relatively small ΔE between the highest occupied molecular orbital and the lowest unoccupied molecular orbital and large negative charge in its two sulfur atoms, which facilitate formation of an insulating Cu/APDTC film on copper surface.     

Intramolecular synergistic effect of glutamic acid, cysteine and glycine against copper corrosion in hydrochloric acid solution

The corrosion protection of copper by glutamic acid, cysteine, glycine and their derivative (glutathione) in 0.5 M hydrochloric acid solution has been studied by the electrochemical impedance spectroscopy and cyclic voltammetry. The inhibition efficiency of the organic inhibitors on copper corrosion increases in the order: glutathione > cysteine > cysteine + glutamic acid + glycine > glutamic acid > glycine. Maximum inhibition efficiency for cysteine reaches about 92.9% at 15 mM concentration level. The glutathione can give 96.4% inhibition efficiency at a concentration of 10 mM. The molecular structure parameters were obtained by PM3 (Parametric Method 3) semi-empirical calculation. The intramolecular synergistic effect of glutamic acid, cysteine and glycine moieties in glutathione is attributed to the lower energy of the lowest unoccupied molecular orbital (E_LUMO) level and to the excess hetero-atom adsorption centers and the bigger coverage on the copper surface.     

Corrosion and ion release behavior of ultra-fine grained bulk pure copper fabricated by ECAP in Hanks solution as potential biomaterial for contraception

Ultra-fine grained (UFG) bulk pure copper has been successfully fabricated by equal-channel angular pressing (ECAP), with the grain size about 380 nm after 8 passes. The potentiodynamic polarization results of the ECAP copper specimens tested in Hanks solution revealed that the corrosion current of UFG copper is higher than that of the coarse grained copper. The cupric ion release behaviors of UFG copper immersed in Hanks solution for 30 days only displayed a burst release during the first 3 days (in comparison to the 1-2 months for the conventional Cu) from 115 μg/day to 12.5 μg/day, after which the ion release remained constant and slow. During the immersion experiments, Cu₂O was the only corrosion product found on the surface and it took 10 days or so to form a uniform Cu₂O layer. Uniform corrosive damage on the surface and few localized corrosion is observed. The above results indicate that UFG copper could have high potential as biomedical materials for contraception.     

Investigation of inhibition effect of rhodanine-N-acetic acid on mild steel corrosion in HCl solution

Corrosion inhibition effect of rhodanine-N-acetic acid (R-NA) on mild steel (MS) corrosion in 0.1 M HCl solution was investigated. For this purpose, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) as well as hydrogen gas evolution (VH₂−t) and the change of open circuit potential as a function of immersion time (E_ocp − t) were used. The MS surfaces exposed to 0.1 M HCl solution in the absence and presence of inhibitor were examined by scanning electron microscopy (SEM). The thermodynamic parameters of adsorption were calculated and discussed. In order to gain more information about the adsorption mechanism, the EIS technique was used to evaluate the potential of zero charge (PZC) and a mechanism of adsorption process was proposed. It was found that, R-NA is a good corrosion inhibitor for the MS corrosion in 0.1 M HCl solution. The inhibition efficiency increased with increasing inhibitor concentration and reached 98% at 1.0 × 10⁻² M R-NA. The high inhibition efficiency was related to adsorption of R-NA on steel surface. Surface SEM images showed a good surface coverage of inhibitor on the metal surface.     

The corrosion inhibition and adsorption behavior of Uncaria gambir extract on mild steel in 1 M HCl

The inhibitive effect of the ethyl acetate extract of Uncaria gambir on the corrosion of mild steel in 1 M HCl solution has been investigated by weight loss measurement as well as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The presence of this catechin-containing extract reduces remarkably the corrosion rate of mild steel in acidic solution. The effect of temperature on the corrosion behavior of mild steel was studied in the range of 303–333 K. The results from this corrosion test clearly reveal that the extract behaves as a mixed type corrosion inhibitor with the highest inhibition at 1000 ppm. Surface analyses via scanning electron microscope (SEM) shows a significant improvement on the surface morphology of the mild steel plate. Linearity of Langmuir isotherm adsorptions indicated the monolayer formation of inhibitor on mild steel surface.     

Mechanisms of hardening, wear and corrosion improvement of 316 L stainless steel by low energy high current pulsed electron beam surface treatment

The mechanisms of corrosion and wear improvements by low energy high current pulsed electron beam (LEHCPEB) have been investigated for an AISI 316 L steel. Selective purification followed by epitaxial growth occurred in the top surface melted layer (2-3 μm thick) that was softened by tensile stresses and, to a much lower extent, by lower efficiency of MnS precipitation hardening. Electrochemical impedance spectroscopy and potentiodynamic polarization analyses used to model the corrosion behavior revealed that, while craters initiated at MnS inclusions initially served as pitting sites, the resistance was increased by 3 orders of magnitude after sufficient number of pulses by the formation of a homogeneous covering layer. The wear resistance was effectively improved by sub-surface (over 100 μm) work hardening associated with the combine effect of the quasi-static thermal stress and the thermal stress waves. The overall results demonstrate the potential of the LEHCPEB technique for improving concomitantly the corrosion and wear performances of metallic materials.     

Microstructure and corrosion behavior of electrodeposited nickel prepared from a sulphamate bath

Electrodeposited nickel was prepared from a sulphamate bath at different current densities ranging from 0.01 A cm^− 2 to 0.1 A cm^− 2. Based on the analysis of the microstructure, the corrosion behavior of the electrodeposited nickel in 3.5%NaCl solution was studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). All the electrodeposits display active-passive-transpassive behavior in potentiodynamic polarization process. The electrodeposits with the best corrosion resistance are obtained at 0.05 A cm^− 2. As for other electrodeposits, the corrosion potential and breakdown potential decrease with increasing current density used to prepare electrodeposits. However, the variation of both corrosion current density and passive current density is opposite to that of the corrosion potential. The changes in the charge-transfer resistance determined from the impedance spectra are consistent with the results determined from potentiodynamic measurements.     

A novel corrosion self-protective copper/liquid microcapsule composite coating

Traditional methods to protect copper coating still exists with some shortages such as environmental pollution and high cost caused by multi-step processes. In this letter, Cu/liquid microcapsule composite coating was prepared by electroplating method. The corrosion resistance of the composite was investigated by means of electrochemical technique. The result of the XPS analysis proved that a thin hydrophobic film could form on the composite surface because of the slow release of microcapsules. This film improved greatly the corrosion resistance of composite coating. Especially, the corrosion inhibition efficiency reached up to 97.6% compared with that of the copper coating when the composite was stored in air for 30 days (d) at 25 °C.     

The effect of extrusion speed on the structure and corrosion properties of aged and non-aged 6063 aluminum alloy

Extrusion is used in processing of Al alloy for consolidation, redistribution of reinforcements, and shape forming. The important parameter that controls the extrusion process is extrusion rate, which is a function of extrusion equipment and parameters. Homogenized AA6063 alloy billets were extruded at different ram speeds related to extrusion speed (3, 6, 10 mm s⁻¹) and then aged at 185 °C for 6 h. The extruded samples were studied for their corrosion, microstructure, and mechanical properties. The effects of extrusion speed and aging on the corrosion behavior of AA6063 were investigated using dynamic polarization and impedance techniques in 0.5 M NaCl aqueous solution. The surface structures were then characterized by means of surface profilometer. The electrochemical measurements showed that the decreasing ram speed for the aged sample improved the corrosion resistance. In addition, the aging improved the corrosion resistance of aluminum in 0.5 NaCl environments.     

Hydroxyapatite coating on the Ti-35Nb-xZr alloy by electron beam-physical vapor deposition

The aim of this study was to investigate the hydroxyapatite coating on the Ti-35Nb-xZr alloy by electron beam-physical vapor deposition. The Ti-35Nb-xZr ternary alloys contained from 3 wt.% to 10 wt.% Zr content were manufactured by arc melting furnace. Hydroxyapatite (HA) coatings were prepared by electron-beam physical vapor deposition (EB-PVD) method, and crystallization treatment was performed in Ar atmosphere at 300 and 500 °C for 1 h. The coated surface morphology of Ti-35Nb-xZr alloy was examined by FE-SEM, EDX and XRD, respectively. In order to evaluate the corrosion behavior, the tests were performed by potentiodynamic, cyclic polarization and AC impedance test. All the electrochemical data were obtained using a potentiostat. The Ti-35Nb-xZr alloys exhibited equiaxed structure with β phase, the peak of β phase increased with Zr contents. The hardness and elastic modulus of Ti-35Nb-xZr alloys decreased as Zr content increased. The HA coated layer was approximately 150 nm and Ca/P ratio of HA coated surface after heat treatment at 500 °C was around 1.67. The HA thin film consisted of small droplets with spherical shape by crystallization. From the anodic polarization curves, HA coated and heat treated Ti-35Nb-10Zr alloy showed higher corrosion potential than other samples. HA coated film on the Ti-35Nb-10Zr alloy can be shown high polarization resistance by crystallization.     

Studies of the corrosion inhibition of copper in sodium chloride solutions using chemical and electrochemical measurements

The inhibiting effects of 2-mercapto-4-amino-5-nitroso-6-hydroxy pyrimidine (MAP) at various concentrations on the copper corrosion in 3.5% NaCl solutions at 25 °C are examined. The inhibiting efficiency of MAP is evaluated from weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) measurements. Experimental investigations showed that MAP reduces markedly the copper corrosion in 3.5% NaCl solutions, and this reduction in corrosion rates enhances with increasing concentration of this compound. The results obtained from the different corrosion evaluation techniques are in good agreement. Polarization curves indicate that MAP is a mixed-type inhibitor. The results of EIS indicate that the value of CPEs tends to decrease and both charge transfer resistance and inhibition efficiency tend to increase by increasing the inhibitor concentration. EFM can be used as a rapid and non-destructive technique for corrosion rate measurements without prior knowledge of Tafel constants.     

Corrosion protection of ENIG surface finishing using electrochemical methods

Four types of thin film coating were carried out on copper for electronic materials by the electroless plating method at a pH range from 3 to 9. The coating performance was evaluated by electrochemical impedance spectroscopy and potentiodynamic polarization testing in a 3.5 wt.% NaCl solution. In addition, atomic force microscopy and X-ray diffraction were also used to analyze the coating surfaces. The electrochemical behavior of the coatings was improved using the electroless nickel plating solution of pH 5. The electroless nickel/immersion gold on the copper substrate exhibited high protective efficiency, charge transfer resistance and very low porosity, indicating an increase in corrosion resistance. Atomic force microscopy and X-ray diffraction analyses confirmed the surface uniformity and the formation of the crystalline-refined NiP {1 2 2} phase at pH 5.     

Electrochemical behaviour of aluminium alloys containing indium and tin in NaCl solution

The electrochemical behaviour of Al, Al–In, Al–Sn and Al–Sn–In alloys in 2 M NaCl solution has been studied using an open circuit potential, potentiodynamic polarization and ac impedance measurements as well as by optical microscopy examination. The addition of alloying components to aluminium produced in all cases a considerable activation of aluminium. The activation is manifested by shifting the open corrosion potential and the pitting potential in the negative direction (for about 0.6 V) and significant reducing of the passive potential region. The degree of activation depended on alloying element and it was found that there is an increase in the order: Al < Al–In < Al–Sn ≈ Al–Sn–In. The anodic dissolution of the Al–Sn and Al–Sn–In alloys started at open circuit potential which is only 0.45 V more positive than the thermodynamic Al³⁺/Al potential. The ac impedance measurements performed at different potentials in wide potential range (corresponding to passive and active state of each examined samples) confirmed the great activity of Al–Sn and Al–Sn–In alloys compared to aluminium.     

Adsorption and corrosion inhibition effect of 2-((5-mercapto-1,3,4-thiadiazol-2-ylimino)methyl)phenol Schiff base on mild steel

In this study, the inhibition effect of 2-((5-mercapto-1,3,4-thiadiazol-2-ylimino)methyl)phenol Schiff base (MTMP) on mild steel corrosion in 0.5 M HCl solution was studied. For this aim, electrochemical techniques such as potentiodynamic polarization curves, weight loss (WL), electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) were used. It was shown that, the MTMP Schiff base has remarkable inhibition efficiency on the corrosion of mild steel in 0.5 M HCl solution. Polarization measurements indicated that, the studied inhibitor acts as mixed type corrosion inhibitor with predominantly control of cathodic reaction. The inhibition efficiency depends on the concentration of inhibitor and reaches 97% at 1.0 mM MTMP. The remarkable inhibition efficiency of MTMP was discussed in terms of blocking of electrode surface by adsorption of inhibitor molecules through active centers. The adsorption of MTMP molecules on the mild steel surface obeys Langmuir adsorption isotherm.     

Surface modification of magnesium alloy AZ31 by hydrofluoric acid treatment and its effect on the corrosion behaviour

In the present study, the effect of hydrofluoric acid (HF) treatment on the surface composition and corrosion behaviour of the magnesium alloy AZ 31 was investigated. The HF treatment of the samples was performed with various concentrations and at different treatment times. The samples surfaces were analysed by Fourier transform infrared spectroscopy, optical emission spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. The results showed the formation of hydroxides, oxides and compounds of the general formula Mg(OH)_xF_2 − x on the samples surfaces, as well as variations on impurities concentrations. The process led to distinct surfaces, each having its specific corrosion resistance, which was evaluated by electrochemical impedance spectroscopy and potentio-dynamic polarization. The most improved corrosion protection was achieved using the concentrations of 14 and 20 mol L^− 1 and 24 h of treatment time, resulting in corrosion rates 20 times lower than those of untreated samples. These two solutions also resulted in an improved corrosion protection for further polymeric coatings, showing that this treatment is an excellent pre-treatment for corrosion protective layers on magnesium alloys.     

The effect of pure iron in a nanocrystalline grain size on the corrosion inhibitor behavior of sodium benzoate in near-neutral aqueous solution

The effect of grain size reduction on the electrochemical and corrosion behavior of iron with different grain sizes (32–750 nm) produced by direct and pulsed current electrodeposition were characterized using Tafel polarization curves and electrochemical impedance spectroscopy. The grain size of deposits was determined by X-ray diffraction analysis and scanning electron microscopy. The tests were carried out in an aqueous electrolyte containing 30 mg L⁻¹ NaCl + 70 mg L⁻¹ Na₂SO₄. Results obtained suggested that the inhibition effect and corrosion protection of sodium benzoate inhibitor in near-neutral aqueous solutions increased as the grain size decreased from microcrystalline to nanocrystalline. The improvement on the inhibition effect is attributed to the increase of the surface energy.     

Copper corrosion inhibition by Azadirachta indica leaves extract in 0.5 M sulphuric acid

Azadirachta indica leaves extract (AI) was investigated as a copper corrosion inhibitor in 0.5 M sulphuric acid. Inhibition efficiency of AI was compared to that of the already proven good inhibitors 2-acetamino-5-mercapto-1,3,4-thiadiazole (AAMTDA) and 1,2,3-benzotriazole (BTAH). The inhibition properties were studied using electrochemical polarization and weight loss techniques. In the region of active copper dissolution, the highest inhibition efficiency was exhibited by AAMTDA (92.7%). AI exhibited somewhat higher efficiency (86.4%) than the widely used BTAH (85.5%), showing that the extract could serve as a effective substitute for currently preferred copper corrosion inhibitors in sulphuric acid. The weight loss results were interpreted by means of the Frumkin isotherm of adsorption on the metal surface. The values of ΔG_ads equal to − 41.96 kJ mol^− 1 for AAMTDA and − 35.22 kJ mol^− 1 for BTAH indicate strong spontaneous adsorption while the surface coverage dependence on the log c following the Frumkin isotherm is suggestive of chemisorption in case of all three tested inhibitors.     

Corrosion resistance of multilayer coatings of nanolayered Cr/Ni electrodeposited from Cr(III)-Ni(II) bath

In this study the corrosion resistance of chromium and nickel single layers and multilayer coatings of nanolayered Cr/Ni, electrodeposited from Cr(III)-Ni(II) baths on low carbon steel substrates, has been studied. The coatings were electrodeposited from a bath using pulse current and modulated agitation. The total thickness of single layer and multilayer coatings was fixed at 5 μm and multilayer coatings with different modulation wavelengths and Cr to Ni thickness ratio were electrodeposited. Corrosion behavior of coatings was then studied by using potentiodynamic polarization test and electrochemical impedance spectroscopy in 0.1 M H₂SO₄. The results showed that Cr and Ni single layers had low corrosion resistance due to the presence of surface cracks and pores, respectively. On the other hand, optimized 20 nm Cr/50 nm Ni multilayer deposition significantly improved corrosion resistance.     

Influence of surface roughness on the corrosion behaviour of magnesium alloy

In this study, the influence of surface roughness on the passivation and pitting corrosion behaviour of AZ91 magnesium alloy in chloride-containing environment was examined using electrochemical techniques. Potentiodynamic polarisation and electrochemical impedance spectroscopy tests suggested that the passivation behaviour of the alloy was affected by increasing the surface roughness. Consequently, the corrosion current and the pitting tendency of the alloy also increased with increase in the surface roughness. Scanning electron micrographs of 24 h immersion test samples clearly revealed pitting corrosion in the highest surface roughness (Sa 430) alloy, whereas in the lowest surface roughness (Sa 80) alloy no evidence of pitting corrosion was observed. Interestingly, when the passivity of the alloy was disturbed by galvanostatically holding the sample at anodic current for 1 h, the alloy underwent high pitting corrosion irrespective of their surface roughness. Thus the study suggests that the surface roughness plays a critical role in the passivation behaviour of the alloy and hence the pitting tendency.