Dynamic electrochemical impedance spectroscopy and polarization studies to evaluate the inhibition effect of benzotriazole on copper‐manganese‐aluminium alloy in artificial seawater

The effect of benzotriazole (BTA) on the corrosion of a new type copper‐manganese‐aluminium (CMA) alloy in artificial seawater was investigated using dynamic electrochemical impedance spectroscopy (DEIS), linear polarization resistance, and Tafel extrapolation methods. Measurement results obtained from those three methods showed that corrosion rates decreased while BTA concentration increased. This clearly indicates that BTA inhibits the corrosion rate of CMA in artificial seawater. Although there are consistent results obtained from all these three methods, the results of the percent inhibition efficiency, IE (%), values obtained from DEIS method should be calculated from the charge transfer resistance (R_ct) values obtained after 5 h.     

Evaluation of cavitation erosion–corrosion degradation of mild steel by means of dynamic impedance spectroscopy in galvanostatic mode

Cavitation erosion and corrosion of mild steel was studied by means of a vibratory facility in 3% w/w NaCl solution. Dynamic Electrochemical Impedance Spectroscopy (DEIS) measurements were carried out in the galvanostatic mode to allow on-line monitoring of impedance parameters in cavitation failure. The results, based on an analysis of instantaneous impedance spectra, correspond to degradation under the influence of cavitation erosion–corrosion. It has been shown that a change of pseudo-capacitance corresponds to an increase in sample roughness, while the charge-transfer resistance determines changes in the corrosion rate under the combined mechanical and electrochemical factors.     

Cefotaxime sodium: A new and efficient corrosion inhibitor for mild steel in hydrochloric acid solution

The corrosion inhibition of mild steel in 1 M HCl solution by cefotaxime sodium has been studied by Tafel polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurement. The inhibitor showed 95.8% inhibition efficiency at optimum concentration 300 ppm. Results obtained revealed that inhibition occurs through adsorption of the cefotaxime on metal surface without modifying the mechanism of corrosion process. Potentiodynamic polarization studies suggest that it is a mixed type of inhibitor. Electrochemical impedance spectroscopy techniques were also used to investigate the mechanism of corrosion inhibition.     

Evaluation of localised corrosion behaviour of super austenitic stainless steels using dynamic electrochemical impedance spectroscopy

Potentiodynamic polarisation and dynamic electrochemical impedance spectroscopic (DEIS) measurements were carried out in natural sea water on type 316L SS, Alloy 926 and Alloy 31. In order to study the localised corrosion resistance, the dynamic electrochemical impedance spectroscopy measurements were performed in a wide range of potentials covering corrosion potential (OCP or E_corr), passive region, break down region and dissolution region. In this report we have shown that the impedance measurement in potentiodynamic condition allows simultaneous investigation of the changes in the passive layer structure and the ion transport process that occurs through the passive layer. The Nyquist plots were fitted using nonlinear least square (NLLS) method for different potential regions. Finally, the experimental results of polaraisation data were found in good agreement with that of DEIS measurement.     

Benzyltrimethylammonium iodide as a corrosion inhibitor for steel in phosphoric acid produced by dihydrate wet method process

The inhibition effect of benzyltrimethylammonium iodide (BTAI) on the corrosion of cold rolled steel (CRS) in phosphoric acid produced by dihydrate wet method process (7.0 M H₃PO₄) solution was investigated for the first time by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) methods. The results show that BTAI is a good inhibitor, and the adsorption of BTAI obeys Langmuir adsorption isotherm. Polarization curves show that BTAI behaves as a mixed-type inhibitor. EIS spectra exhibit one capacitive loop and confirm the inhibitive ability. The inhibition action of BTAI is also evidenced by SEM images.     

2-Mercaptobenzimidazole as a copper corrosion inhibitor: Part I. Long-term immersion, 3D-profilometry,and electrochemistry

The high corrosion inhibition effectiveness of 2-mercaptobenzimidazole (MBIH) in 3 wt.% aqueous NaCl solution is reported using long term immersion tests, 3D-profilometry, electrochemical impedance spectroscopy, and potentiodynamic curve measurements. The high corrosion inhibition performance was proven after 180 days of immersion. The impedance spectra were characterized by two time constants relating to charge transfer and finite layer thickness or semi-infinite diffusion of copper ions through the surface layer, therefore Cu corrosion in solution containing MBIH follows kinetic-controlled and diffusion-controlled processes. Moreover, it is shown that MBIH is a mixed-type inhibitor.     

Crevice corrosion behaviour of superaustenitic stainless steels: Dynamic electrochemical impedance spectroscopy and atomic force microscopy studies

Potentiodynamic anodic polarisation and dynamic electrochemical impedance spectroscopic (DEIS) measurements were carried out for 316L SS, alloy 33 and alloy 24 in natural sea water in order to assess their crevice corrosion resistance. DEIS measurements were performed from open circuit potential to dissolution potential. It was shown that the impedance measurements in potentiodynamic conditions allow simultaneous investigation of changes in passive layer structure. The impedance spectra of various potential regions were also discussed. The surface morphology of the alloys after crevice corrosion studies were studied using optical microscope and atomic force microscopy (AFM).     

The effects of pharmaceutically active compound doxycycline on the corrosion of mild steel in hydrochloric acid solution

Corrosion inhibition of mild steel in hydrochloric acid solution by doxycycline has been studied by weight loss measurements, polarization resistance, Tafel polarization and electrochemical impedance spectroscopy. The inhibitor showed more than 95% inhibition efficiency at optimum concentration 9.02 × 10⁻⁴ M. Potentiodynamic polarization suggests that it is a mixed type of inhibitor. Electrochemical impedance spectroscopy was used to investigate the mechanism of corrosion inhibition. Thermodynamic parameters were calculated to investigate mechanism of inhibition. The compound follows Langmuir adsorption isotherm. AFM studies of mild steel surface with and without inhibitor were performed and calculated roughness also supported the inhibition data.     

A study of the inhibition of iron corrosion in HCl solutions by some amino acids

The performance of three selected amino acids, namely alanine (Ala), cysteine (Cys) and S-methyl cysteine (S-MCys) as safe corrosion inhibitors for iron in aerated stagnant 1.0 M HCl solutions was evaluated by Tafel polarization and impedance measurements. Results indicate that Ala acts mainly as a cathodic inhibitor, while Cys and S-MCys function as mixed-type inhibitors. Cys, which contains a mercapto group in its molecular structure, was the most effective among the inhibitors tested, while Ala was less effective than S-MCys. The low inhibition efficiency recorded for S-MCys compared with that of Cys was attributed to steric effects caused by the substituent methyl on the mercapto group. Electrochemical frequency modulation (EFM) technique and inductively coupled plasma atomic emission spectrometry (ICP-AES), were also applied to make accurate determination of corrosion rates. Validation of the Tafel extrapolation method for measuring corrosion rates was tested. Rates of corrosion rates (in μm y⁻¹) obtained from Tafel extrapolation method are in good agreement with those measured using EFM and ICP methods. Some theoretical studies, including molecular dynamics (MD) and density functional theory (DFT), were also employed to establish the correlation between the structure (molecular and electronic) of the three tested inhibitors and the inhibition efficiency. Adsorption via hydrogen bonding was discussed here based on some theoretical studies. Experimental and theoretical results were in good agreement.     

On the inhibition of mild steel corrosion by 4-amino-5-phenyl-4H-1, 2, 4-trizole-3-thiol

The corrosion inhibition of mild steel in a 2.5 M H₂SO₄ solution by 4-amino-5-phenyl-4H-1, 2, 4-trizole-3-thiol (APTT) was studied at different temperatures, utilising open circuit potential, potentiodynamic and impedance measurements. The results indicate that APTT performed as an excellent mixed-type inhibitor for mild steel corrosion in a 2.5 M H₂SO₄ solution and that the inhibition efficiencies increased with the inhibitor concentration but decreased proportionally with temperature. The kinetic and thermodynamic parameters for adsorption of APTT on the mild steel surface were calculated. A chemisorption mechanism of APTT molecules on the mild steel surface was proposed based on the thermodynamic adsorption parameters.     

Synthesis and evaluation of Tris-hydroxymethyl-(2-hydroxybenzylidenamino)-methane as a corrosion inhibitor for cold rolled steel in hydrochloric acid

Tris-hydroxymethyl-(2-hydroxybenzylidenamino)-methane (THHM) was synthesized. The effect of THHM on the corrosion of cold rolled steel (CRS) in 0.1 M hydrochloric acid was then investigated by Tafel polarization curve and electrochemical impedance spectroscopy (EIS). Polarization curve results clearly reveal the fact that THHM is a good cathodic type inhibitor. EIS results confirm its corrosion inhibition ability. The inhibition efficiency increases with increasing THHM concentration but decreases with immersion time. Atomic force microscopy (AFM) reveals that a protective film forms on the surface of the inhibited sample. The adsorption of this inhibitor is found to follow the Langmuir adsorption isotherm. THHM adsorbs on the sample probably by chemisorption.     

Corrosion inhibition of mild steel by ethylamino imidazoline derivative in CO2-saturated solution

The corrosion inhibition and adsorption behaviour of 2-undecyl-1-ethylamino imidazoline (2UEI) on N80 mild steel in CO₂-saturated 3% NaCl solutions was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy techniques and SEM observation. Inhibitor efficiency increased with increase in 2UEI concentration. Temperature studies revealed an increase in inhibition efficiency with rise in temperature and corrosion activation energies decreased in the presence of 2UEI. A mechanism of chemical adsorption of 2UEI on the metal’s surface is proposed. The adsorption characteristics of the inhibitor were approximated by Temkin isotherm. The inhibition efficiency of 2UEI was enhanced in the presence of iodide ions.     

Investigation of the inhibition effect of 5-((E)-4-phenylbuta-1,3-dienylideneamino)-1,3,4-thiadiazole-2-thiol Schiff base on mild steel corrosion in hydrochloric acid

The inhibition effect of 5-((E)-4-phenylbuta-1,3-dienylideneamino)-1,3,4-thiadiazole-2-thiol (PDTT) Schiff base on mild steel corrosion in 0.5 M HCl was studied for both short and long immersion time. For this purpose, potentiodynamic polarization, electrochemical impedance spectroscopy, linear polarization resistance, hydrogen gas evolution, the change of open circuit potential as a function of immersion time, SEM and AFM techniques were utilized. The PDTT Schiff base has shown remarkable inhibition on the corrosion of mild steel in 0.5 M HCl solution. The high inhibition efficiency was attributed to the blocking of active sites by adsorption of inhibitor molecules on the steel surface.     

Corrosion and corrosion control of mild steel in concentrated H2SO4 solutions by a newly synthesized glycine derivative

A newly synthesized glycine derivative (GlyD1), 2-(4-(dimethylamino)benzylamino)acetic acid hydrochloride, was used to control mild steel corrosion in 4.0 M H₂SO₄ solutions at different temperatures (278–338 K). Tafel extrapolation, linear polarization resistance (LPR) and impedance methods were used to test corrosion inhibitor efficiency. An independent method of chemical analysis, namely ICP-AES (inductively coupled plasma atomic emission spectrometry) was also used to test validity of corrosion rate measured by Tafel extrapolation method. Results obtained were compared with an available glycine derivative (GlyD2) and glycine (Gly). Tafel polarization measurements revealed that the three tested inhibitors function as mixed-type compounds. The inhibition efficiency increased with increase in inhibitor concentration and decreased with temperature, suggesting the occurrence of physical adsorption. The adsorptive behaviour of the three inhibitors followed Temkin-type isotherm and the standard free energy changes of adsorption () were evaluated for the three tested inhibitors as a function of temperature. The inhibition performance of GlyD1 was much better than those of GlyD2 and Gly itself. Results obtained from the different corrosion evaluation techniques were in good agreement.     

Electrochemical techniques for practical evaluation of corrosion inhibitor effectiveness. Performance of cerium nitrate as corrosion inhibitor for AA2024T3 alloy

In this work, a split-cell technique and image-assisted electrochemical noise analysis, which provide minimal perturbation of the freely corroding system and good time resolution, are proposed as a tool for simultaneous investigation of the corrosion inhibition mechanism and assessment of performance. The results obtained are compared with results from traditional electrochemical impedance spectroscopy, disclosing the advantages of these techniques in the evaluation of inhibitor performance. Specific attention is also given to the investigation of corrosion inhibition by cerium nitrate.     

Influence of iron microstructure on the performance of polyacrylic acid as corrosion inhibitor in sulfuric acid solution

The corrosion inhibition behavior of bulk nanocrystalline ingot iron (BNII) fabricated from coarse polycrystalline ingot iron (CPII) by severe rolling technique by polyacrylic acid (PAA) was studied in 0.1 M H₂SO₄ using electrochemical impedance spectroscopy and potentiodynamic polarization techniques. The results indicated that PAA inhibited the acid induced corrosion of both iron specimens, with greater effect noted for BNII. The corrosion inhibiting effect was influenced by the microstructure of the iron samples. Synergistic inhibition effect was observed on addition of iodide ions to PAA in case of CPII while for BNII inhibition efficiency marginally increased.     

Inhibition effect of methyl violet on the corrosion of cold rolled steel in 1.0 M HCl solution

The inhibition effect of methyl violet (MV) on the corrosion of cold rolled steel (CRS) in 1.0 M HCl solution at 20-50 °C was studied by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) methods. The results show that MV is an excellent inhibitor even with very low concentration, and the adsorption of MV on CRS surface obeys Langmuir adsorption isotherm. Potentiodynamic polarization curves reveal that MV behaves as a mixed-type inhibitor. EIS spectra exhibit one capacitive loop and confirm the inhibitive ability. The inhibition action of MV is also evidenced by SEM.     

Blue tetrazolium as a novel corrosion inhibitor for cold rolled steel in hydrochloric acid solution

The inhibition effect of blue tetrazolium (BT) on the corrosion of cold rolled steel (CRS) in 1.0 M HCl solution at 20 °C was investigated by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) methods. The results show that BT is a very good inhibitor, and the adsorption of BT on CRS surface obeys Langmuir adsorption isotherm. Polarization curves reveal that BT acts as a mixed-type inhibitor. EIS spectra exhibit one capacitive loop and confirm the inhibitive ability. The inhibition action of BT is also evidenced by SEM images.     

Inhibiting effect of 2-mercaptobenzimidazole on the corrosion of Cu-30Ni alloy in aerated 3% NaCl in presence of ammonia

The inhibiting effect of 2-mercaptobenzimidazole (MBI) against Cu-30Ni alloy corrosion in aerated 3% NaCl polluted by ammonia, has been developed. Potentiodynamic and electrochemical impedance spectroscopy (EIS) measurements have been applied to determine the corrosion rate. scanning electron microscopy (SEM) studied surface morphology has been used to characterise electrode surface. The obtained results indicate that MBI acts as a good mixed-type inhibitor retarding the anodic and cathodic reactions. An increase of MBI concentration leads to a decrease of corrosion rate and inhibition efficiency increase.     

Corrosion inhibition of C38 steel in 1 M hydrochloric acid medium by alkaloids extract from Oxandra asbeckii plant

The inhibition effect of alkaloids extract from Oxandra asbeckii plant (OAPE) on the corrosion of C38 steel in 1 M hydrochloric acid solution has been investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The corrosion inhibition efficiency increases on increasing plant extracts concentration. Cathodic and anodic polarization curves show that OAPE is a mixed-type inhibitor. The effect of temperature on the corrosion behavior of C38 steel in 1 M HCl with and without addition of plant extract was studied in the temperature range 25–55 °C. The thermodynamic functions of dissolution and adsorption processes were calculated from experimental polarization data and the interpretation of the results are given. The adsorption of this plant extract on the C38 steel surface obeys the Langmuir adsorption isotherm. Surface analysis (Raman) was also carried out to establish the corrosion inhibitive property of this plant extract in HCl solution.