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.     

Electrochemical performance of diamond-like carbon thin films

Diamond-like carbon (DLC) thin films used in this study were intended for their electrochemical properties. The DLC films were deposited by a filtered cathodic vacuum arc (FCVA) process on p-type silicon (100) substrates biased at different pulse voltages (0-2000 V). The chemical bonding structures of the DLC films were characterized with micro-Raman spectroscopy and the electrochemical properties were evaluated by means of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The DLC films showed high impedance, high polarization resistance and high breakdown potential in a 0.5 M H₂SO₄ aqueous solution, which were attributed to the high sp³ content and uniformity of the films. The excellent chemical inertness of the DLC films made them promising corrosion resistant coating materials.     

Electrochemical properties of TiN coatings on 316L stainless steel separator for polymer electrolyte membrane fuel cell

TiN films for metallic bipolar plates were synthesized by closed-field unbalanced magnetron sputtering (CFUBM) and the properties were controlled by adjusting the N₂ partial pressure. The corrosion behaviors of TiN films were investigated by potentiodynamic tests and electrochemical impedance spectroscopy (EIS) measurements under the condition of an aerated 1 M H₂SO₄ + 2 ppm HF solution at 70 °C with a constant potential of 600 mV_SCE. The results revealed that the variation of N₂ pressure had an influence on the corrosion resistance of TiN coating. N₂ partial pressure of 0.4 mTorr showed good corrosion resistance with the lowest corrosion current density and the highest charge transfer resistance due to the low porosity.     

Corrosion behavior of bulk amorphous Zr55Al10Cu30Ni5−xPdx alloys

Bulk amorphous Zr₅₅Al₁₀Cu₃₀Ni_5−xPd_x (x=0, 5at.%) alloys were produced by copper mould casting. The microstructure of samples was characterized by X-ray diffraction (XRD). The corrosion resistance of the bulk amorphous alloys was studied by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). The Pd-free alloy showed an active–passive transition by anodic polarization in 3.5% NaCl solution, it was spontaneously passive and had a wide passive region with significantly low passive current density. The 5% Pd amorphous alloy shows a single active state even with a limited passive region. X-ray photoelectron spectroscopy (XPS) analysis revealed that the spontaneous passive films formed on the alloys after immersion in 0.6 M NaCl solution for 72 h were composed of the oxidation of Zr, Al and Cu element. The Pd-free and 5% Pd alloys show excellent corrosion properties in 1 M NaOH solution.     

Poly(N-methyl aniline) thin films on copper: Synthesis, characterization and corrosion protection

Poly(N-methyl aniline) (PNMA) coatings were synthesized on copper by electrochemical polymerization of N-methyl aniline in aqueous oxalic acid solution by using cyclic voltammetry. The optimum electrodeposition conditions (e.g. upper potential limit, scan rate and cycle number) were determined in order to obtain PNMA coatings to have the best corrosion performance. PNMA coatings were characterized by cyclic voltammetry, Fourier Transform Infrared-Attenuated Total Reflectance spectroscopy and scanning electron microscopy. Redox parameters found after electrochemical tests indicate a thin film character and diffusion controlled electroactive behavior of PNMA. Corrosion test results revealed that PNMA coating appears to enhance protection of copper in 0.1 M H₂SO₄ solution.     

Pitting corrosion protection of low nickel stainless steel by electropolymerized conducting polymer coating in 0·5?M NaCl solution

Conducting polymers of polyaniline (PANi) and poly(o-phenylenediamine) (PoPD) were electropolymerized by cyclic voltammetric technique on low nickel stainless steel (LN SS) in H₂SO₄solution containing aniline and o-phenylenediamine monomers. The coatings were characterized by Fourier transform infrared spectroscopy, UV-visible and scanning electron microscopic techniques and the results are discussed. The corrosion protective properties of PANi and PoPD coatings on LN SS in 0·5 M NaCl were evaluated using potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) techniques. The potentiodynamic polarization and electrochemical impedance spectroscopic results indicate that the PoPD coating inhibits the corrosion of LN SS in 0·5 M NaCl solution more effectively than PANi.     

Photosensitive self-assembled membrane of cysteine against copper corrosion

Complex self-assembled membrane (SAM) was prepared by modifying the adsorption of cysteine with fluorescent reagent sodium 1-naphthylamine diacetate (NADA) on copper surface. The SAM has a fluorescence emission at 430 nm. Its protective effects against copper corrosion were investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) in 0.5 M NaCl solution. It suppresses cathodic current densities and shifts the corrosion potential toward more positive values. The variation of the fluorescence intensity is correlated to that of the impedance resistance. The fluorescence detection provides a potential monitoring method for the protection of the SAM on copper surface.     

Langmuir-Blodgett films of polyaniline for low density lipoprotein detection

Langmuir-Blodgett (LB) films of polyaniline (PANI) were utilized for the fabrication of impedimetric immunosensor for detection of human plasma low density lipoprotein (LDL) by immobilizing anti-apolipoprotein B (AAB) via EDC-NHS coupling. The modified electrodes were characterized by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy. AAB/PANI-SA LB immunoelectrodes studied by EIS spectroscopy revealed detection of LDL in the wide range of 0.018 μM (6 mg/dl) to 0.39 μM (130 mg/dl), covering the physiological range in blood, with a sensitivity of 11.25 kΩ μM^− 1.     

Green approach to corrosion inhibition of mild steel in two acidic solutions by the extract of Punica granatum peel and main constituents

The effect of the extract of Punica granatum (PG) and their main constituents involve ellagic acid (EA) and tannic acid (TA), as mild steel corrosion inhibitor in 2 M HCl and 1 M H₂SO₄ solutions was investigated by weight loss measurements. The results obtained from the weight loss measurements show that the inhibition efficiency of TA even in high concentration is very low. Thus, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) investigations were used for different concentrations of PG and EA and best concentration of TA. Potentiodynamic polarization curves indicated that PG and EA behave as mixed-type inhibitors. EIS measurements show an increase of the transfer resistance with increasing inhibitor concentration. The temperature effect on the corrosion behavior of steel without and with the PG extract was studied. The inhibition action of the extract was discussed in view of Langmuir adsorption isotherm.     

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.     

Fabrication of hydrophobic/super-hydrophobic nanofilms on magnesium alloys by polymer plating

Hydrophobic/super-hydrophobic nanofilms with improved corrosion resistance were fabricated on the surfaces of Mg-Mn-Ce magnesium alloy by a surface modification technique, named as polymer plating, which has been developed to modify superficial characteristics of magnesium alloys with polymeric nanofilms through synthesized organic compounds of triazine dithiol containing functional groups. The nanofilms were prepared by the electrochemical and polymerization reactions during polymer plating analyzed from characteristics of Fourier transform infrared spectrophotometer, X-ray photoelectron spectroscopy and scanning electron microscopy. The fabricated nanofilms changed the surface wettability of blank magnesium alloy from hydrophilic to hydrophobic with contact angle 119.0° of distilled water with lower surface free energy of 20.59 mJ/m² and even super-hydrophobic with contact angle 158.3° with lowest surface free energy of 4.68 mJ/m² by different functional nanofilms on their surfaces. Alteration of wettability from hydrophilic to hydrophobic and super-hydrophobic resulted from their low surface free energy and surface morphology with micro- and nano-rough structures. The corrosion behaviors from potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) show that the super-hydrophobic nanofilm has higher corrosion resistance and stability in 0.1 mol/L NaCl solution and lower corrosion current density (I_corr) with R_ct increasing two orders of magnitude of 16,500 Ω·cm² compared to that obtained for blank of 485 Ω·cm².     

The inhibition of mild steel corrosion in 1 M hydrochloric acid solutions by triazole derivative

The title compound 1-(4,5-dihydro-3-phenylpyridine-1-yl)-2-(1H-1,2,4-triazole-1-yl)ethyl ketone (DTE) was synthesized and its inhibiting action on the corrosion of mild steel in 1 M hydrochloric acid solutions was investigated by means of weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electronic microscope (SEM). Results obtained revealed that DTE performed excellently as a corrosion inhibitor for mild steel in 1 M hydrochloric acid media and its efficiency attains more than 90.9% at 1.0 × 10^− 3 M at 298 K. Polarization curves indicated that the inhibitor behave mainly as mixed-type inhibitor. EIS showed that the charge transfer controls the corrosion process in the uninhibited and inhibited solutions. Adsorption of the inhibitor on the mild steel surface followed Langmuir adsorption isotherm. And the values of the free energy of adsorption ΔG_ads indicated that the adsorption of DTE molecule was a spontaneous process and was typical of chemisorption.     

Electrochemical impedance spectroscopy investigation on indium tin oxide films under cathodic polarization in NaOH solution

The electrochemical corrosion behaviors of indium tin oxide (ITO) films under the cathodic polarization in 0.1 M NaOH solution were investigated by electrochemical impedance spectroscopy. The as-received and the cathodically polarized ITO films were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction for morphological, compositional and structural studies. The results showed that ITO films underwent a corrosion process during the cathodic polarization and the main component of the corrosion products was body-centered cubic indium. The electrochemical impedance parameters were related to the effect of the cathodic polarization on the ITO specimens. The capacitance of ITO specimens increased, while the charge transfer resistance and the inductance decreased with the increase of the polarization time. The proposed mechanism indicated that the corrosion products (metallic indium) were firstly formed during the cathodic polarization and then absorbed on the surface of the ITO film. As the surface was gradually covered by indium particles, the corrosion process was suppressed.     

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.     

Corrosion and impedance studies on magnesium alloy in oxalate solution

Corrosion behavior of AZ91E alloy was investigated in oxalate solution using potentiodynamic polarization and electrochemical impedance measurements (EIS). The effect of oxalate concentration was studied, where the corrosion rate increases with increasing oxalate concentration. The effect of added ions (Br⁻, Cl⁻ or SiO₃²⁻) on the electrochemical behavior of magnesium alloy in 0.1 M Na₂C₂O₄ solution at 298 K, was investigated. It was found that the corrosion rate of 0.1 M oxalate solution containing silicate ion is lower than the blank (0.1 M Na₂C₂O₄). This was confirmed by scanning electron microscope (SEM) observations. However, for the other added ions Br⁻ or Cl⁻, the corrosion rate is higher than the blank.     

Some aspects of corrosion and film formation of austenitic stainless steel type 316LN using electrochemical impedance spectroscopy (EIS)

Corrosion and passive film characteristics of 316LN stainless steel with different degrees of cold work (0–25%) were studied using electrochemical impedance spectroscopy (EIS) and potentiodynamic anodic polarization techniques in deaerated acidic and alkaline (pH = 8) media. EIS measurements were conducted at open circuit potential (OCP) as well as after passivation in these media. Using the capacitance data from EIS measurements, film thickness was calculated. A definite correlation was observed between film thickness and corrosion rate after passivation. Analysis of the series capacitance and series resistance data from the EIS spectra showed that the films formed at OCP and after passivation were of semiconducting type. The nature of the semiconducting type of films was determined to be n-type using the ratios of anodic and cathodic transfer coefficients (α_a/α_c).     

Characterization of bis-[triethoxysilylpropyl] tetrasulfide layers on aluminum based on water-based silanization solution

In this work, a water-based silanization solution was prepared using a biphasic hydrolysis system composed of 85% (V/V) water and 15% (V/V) bis-[triethoxysilylpropyl] tetrasulfide (BTESPT)/n-heptane/ethanol mixture for efficiently coating aluminum with silane layer against corrosion. The BTESPT-based coatings on several pretreated aluminum samples were characterized by scanning electron microscopy and X-ray energy dispersive spectroscopy, and their electrochemical behaviors were assessed in 0.1 M NaCl neutral solution by means of electrochemical impedance spectroscopy and Tafel polarization. The BTESPT-based coating of about 180 nm thick was found to be uniform and compact, and the maximum corrosion resistance of 10⁶ Ω of the BTESPT-treated aluminum samples was observed, which is larger than that of bare aluminum by two orders of magnitude. Durability tests in NaCl solution demonstrated that the BTESPT coating can provide superior protection of alumina substrate from corrosion for 10-day immersion in the corrosive media.     

Electrochemical corrosion behavior of 2A02 Al alloy under an accelerated simulation marine atmospheric environment

The corrosion behavior of 2A02 Al alloy under simulated marine atmospheric environment has been studied using mass-gain, scanning electron microscope/energy dispersive spectroscopy (SEM/EDS), laser scanning confocal microscopy, X-ray diffraction spectroscopy and localized electrochemical methods. The results demonstrate that the relationship between the corrosion induced mass-gain and the corrosion time is in accordance with the power rule. The mass-gain increases gradually during the corrosion time, while the corrosion rate decreases. With ongoing of the corrosion, corrosion products film changed from a porous to a compact structure. The various spectroscopic data show that the corrosion products films composed mainly of Al(OH)₃, Al₂O₃ and AlCl₃. The electrochemical corrosion behavior of the 2A02 Al alloy was studied by electrochemical impedance spectroscopy (EIS).     

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.     

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.