Potentiodynamic Polarization Analysis Research Articles

Silver Linings: Electrochemical Characterization of TiO2 Sol-Gel Coating on Ti6Al4V with AgNO3 for Antibacterial Excellence

This study aimed to synthesize TiO2 and silver-containing TiO2 layers on Ti6Al4V titanium alloy substrates, also known as titanium grade 5 (TiGr5), to provide corrosion resistance and antibacterial activity. The TiO2 layers were prepared through the sol-gel method and dip-coating technique. Silver introduction into the layers was performed in two different ways. One was the impregnation method by dipping the TiO2 layer-covered metal in aqueous AgNO3 solutions of various concentrations (TiO2/AgNO3), and the other was by direct introduction of AgNO3 into the precursor sol (Ag-TiO2). The two methods for incorporating AgNO3 into the coating matrix are novel, as they preserve silver in its ionic form rather than reducing it to metallic silver. The samples were put through electrochemical characterization, namely potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), and were tested in Hank’s solution, simulating a physiological environment. The behavior of the layers was monitored over time. Also, the thin layers’ thickness and adhesion to the substrate were determined. Microbiological evaluation of the Ag-doped coatings on glass substrates confirmed their significant bactericidal activity against Gram-negative Escherichia coli. Among the two types of coatings, the impregnated coatings demonstrated the most promising electrochemical performance, as evidenced by both EIS and potentiodynamic polarization analyses.

Exploring protective mechanisms with triazine ring and hydroxyethyl groups: Experimental and theoretical insights

The current study investigates the protective mechanisms of a novel triazine-based compound, 2,2′,2''-((1,3,5-triazine-2,4,6-triyl)tris (azanediyl))triethanol (TATTE) (for carbon steel protection in 0.5 M sulfuric acid) were investigated. Potentiodynamic polarization and electrochemical impedance spectroscopy analyses unveiled that TATTE serves as a protective agent with a dual inhibitory mechanism, showcasing exceptional efficiency exceeding 96%. Scanning electron microscopy (SEM) observations demonstrated the formation of a protective layer by TATTE on the surface of carbon steel. Density functional theory (DFT) calculations offered valuable insights into the favorable adsorption of both the neutral and protonated forms of TATTE through interactions between their functional groups and the steel surface. Molecular dynamics simulations further substantiated this, revealing that the neutral molecule exhibits physical adsorption, while the protonated form engages in stronger chemical adsorption, as evidenced by binding energies and radial distribution functions. The superior protective mechanism performance observed in our experiments can be attributed to the synergistic adsorption of TATTE, facilitated by the presence of the triazine ring and multiple hydroxyl groups.

Insights into the corrosion inhibition performance of essential oil of Teucrium luteum subsp. flavovirens for carbon steel in 1.0 M HCl medium: experimental and theoretical evaluations

The objective of this research work was to assess Teucrium luteum subsp. flavovirens essential oil (EOTL), for the first time, as novel and eco-friendly corrosion inhibitor for carbon steel (CS) in 1.0 M HCl medium. Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) and surface analysis were employed to assess the effectiveness of the EOTL. The findings indicate that the EOTL reduces the corrosion of CS in hydrochloric acid and offered an inhibition efficiency (IE) of 91% at a dosage of 2.00 g/L at 298 K. The PDP data showed that EOTL behaved as a mixed-type corrosion inhibitor. The effect of immersion time and temperature on the corrosion inhibition performance of EOTL was also studied. It was found that the IE increased only up to 24 h and decreased with prolonged immersion time. In addition, the IE diminished with increasing temperature. The EOTL molecules adsorbed on the CS surface following Langmuir adsorption isotherm, with an adsorption energy ranging from −16 to −27 kJ/mol, an indication of physico-chemical adsorption mechanisms. The SEM/EDX results provide evidence of the presence of a protective film of the inhibitor on the surface of the CS. Theoretical studies using DFT, Monte Carlo simulations, molecular dynamics simulations and mean square displacement were conducted to given insight into the contributions of the four main components of EOTL. This work not only introduces a sustainable alternative to conventional corrosion inhibitors but also provides a robust understanding of the underlying mechanisms, hence contributing to advancement in corrosion science.

Experimental and Computational Insights into the Effects of -NH2 and -Cl Functional Groups on the Copper Corrosion Inhibition by Benzotriazole

The influences of -NH2 and -Cl groups on the copper corrosion inhibition in 0.5 M H2SO4 solution by benzotriazole were studied using experimental methods and density functional theory calculations. Mass loss tests, potentiodynamic polarization, and surface morphology analyses revealed notable differences: while unmodified benzotriazole showed an inhibition efficiency of 76.6%, the -Cl derivative increased this to 87.6%, whereas the -NH2 derivative dropped it to 61.0% at the concentration of 5 × 10−4 M. Density functional theory calculations indicated these differences are not due to electronic properties or inhibitor-copper interaction energies but rather to the inhibitor’s influence on the oxygen reduction reaction, especially O2 and H2O adsorption. The -NH2 group formed strong hydrogen bonds with O2 and H2O, reducing oxygen reduction inhibition, while the -Cl group repelled O2, resulting in enhanced inhibition. Free energy analysis of the oxygen reduction reaction supported these findings. These new insights into benzotriazole derivatives’ copper corrosion inhibition mechanisms offer valuable guidance for developing next-generation corrosion inhibitors.

Mitigation effect of a biodegradable surfactant N,N,N-trimethyl-2-(((hexadecyloxy)carbonyl)oxy)ethan-1-aminiumiodide for mild steel corrosion in 5% HCl: Experimental and theoretical insights

A cleavable cationic surfactant having carbonate linkage, N,N,N-trimethyl-2-(((hexadecyloxy)carbonyl)oxy)ethan-1-aminiumiodide referred to as THC was synthesised and characterized employing elemental analysis, FT-IR (Fourier Transform Infrared Spectroscopy), 1H NMR (Nuclear Magnetic Resonance) and 13C NMR. The extent of corrosion inhibition of THC was for the first time studied experimentally and theoretically on mild steel (MS) substrate in 5 % HCl solution at temperatures 303, 313, 323, 333, 343, 353 K. Experimental investigations include gravimetric analysis, potentiodynamic polarization (PDP) and electrochemical impedance analysis (EIS). THC provided maximum inhibition efficiency of 93.2 % at concentration of 1×10−4 M at 303 K which was further raised to 98.1 % at 353 K. PDP studies reveal that given surfactant is mixed type inhibitor. Surface studies such as contact angle measurement, AFM (Atomic Force Microscopy), SEM-EDX (Scanning Electron Microscope-Energy Dispersive X-ray Analysis), and XPS (X-ray Photoelectron Spectroscopy) were employed to justify the adsorption of inhibitor molecules on MS surface. Furthermore, biodegradability test on THC was done to support the environment friendly nature of the surfactant.

Assessment of Warionia saharea Essential Oil as a Green Corrosion Inhibitor for Mild Steel in HCl: Experimental and Computational Studies

The objective of this research work is the study of the inhibitory effect of Warionia saharea essential oil (WSEO) on the corrosion of mild steel (MS) in molar HCl solution, employing both experimental and theoretical methods. This inhibitory effect (IE) has been evaluated by using a combination of weight loss measurements (LW) and various electrochemical methods, such as open circuit potential (OCP), potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) experiments. The LW results indicated that IE increased with inhibitor concentration, reaching 83.34% at 3.00 g/L. The PDP analysis suggested that WSEO functions as a mixed inhibitor, while in the EIS results the Rct values increased with inhibitor concentration to reach 165.8 Ω cm2 at 2.00 g/L, suggesting a defensive film formation by WSEO molecules over the metallic surface. The thermodynamic study demonstrated that the WSEO molecules adsorption on the MS surface followed a Langmuir isotherm, involving mixed physical and chemical (physicochemical) adsorption on the MS surface. Theoretical methods, including density functional theory (DFT) and molecular dynamics (MD) simulations, were employed to elucidate the inhibition mechanisms of the three main components of WSEO. The quantum chemical analysis, using density functional theory (DFT) and molecular dynamics (MD) simulations, showed a low ΔEgap value of 6.30 eV and a low adsorption energy (Eads) value on an Fe (110) substrate of −258 Kcal/mol for (E)-Nerolidol, indicating the significant contribution of this molecule to the overall corrosion inhibition effect of WSEO. The scanning electron microscope (SEM) analysis verified the presence of a protective film formed by the inhibitor on the MS surface. This study highlights the potential of WSEO as a sustainable and green corrosion inhibitor in acidic environments.

Surface Modification and Corrosion Performance of Laser Cladded Co–Ni on Ti–6Al–4 V in 0.5 M H2SO4 Environment

This study investigates the laser cladding of Co and Ni powders onto Ti–6Al–4 V substrates, varying the admixed percentages while adjusting laser processing parameters. The influence of nickel and cobalt contents on the microstructure, phase composition, and electrochemical behavior of the laser-clad Ti–6Al–4 V coatings were analyzed. Coating morphology and phases were characterized using scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS), and X-ray diffractometry (XRD), respectively. The corrosion resistance of Ti–6Al–4 V, both with and without Ni–Co additions, in 0.5 M H2SO4 was evaluated using potentiodynamic polarization technique. Results indicated that the coatings exhibited excellent metallurgical compatibility with the substrate. Additionally, the high scan speed laser-clad samples showed enhanced corrosion resistance compared to those processed at low speeds. The potentiodynamic polarization analysis revealed passive behavior in all specimens, with higher cobalt content notably enhancing passivity and corrosion resistance by suppressing the anodic reaction.

Eco-friendly corrosion inhibition and scale control in seawater using Foeniculum vulgare and Pimpinella anisum extracts with chemical compounds

This study investigated the corrosion inhibition and scale control properties of both natural extracts and chemical inhibitors for C25 galvanized steel sheets with an 85-μm thick zinc coating steel exposed to seawater. The inhibitors, including Foeniculum vulgare (AF-Sha), Pimpinella anisum (AF-Sim), M640, and Veo, underwent rigorous evaluation through techniques such as Tafel extrapolation, potentiodynamic polarization analysis, concentration factor scale, seawater analysis, X-ray diffraction (XRD), infrared spectroscopy (IR), and conductivity-temperature analysis. Notably, AF-Sha and AF-Sim exhibited outstanding corrosion prevention capabilities, achieving inhibitory efficiencies of 87% and 85%, respectively. Comparative analyses with chemical inhibitors, M640 and Veo, demonstrated promising performance, positioning natural inhibitors as environmentally friendly alternatives. Corrosion rates, inhibition efficiency, and concentration factor scale results provided insights into the inhibitory effectiveness of each compound, with Veo showing superior performance. The study also explored the antiscalant behavior of inhibitors, revealing their ability to prevent corrosion and scale formation. XRD analysis indicated the impact of inhibitors on the crystal structure of scales, while IR spectra provided insights into vibration properties. Conductivity and temperature analyses illustrated the inhibitors' role in reducing ion exchange and gypsum concentration in seawater. These findings suggest that the inhibitors offered robust protection for ferrous metal surfaces and hold significant potential for practical applications. Additionally, our weight loss investigation extends this understanding, demonstrating the practical applicability of corrosion inhibitors like AF-Sha and AF-Sim in real-world scenarios. The presented results contribute significantly to the understanding of galvanized steel corrosion behavior in seawater, offering valuable insights for corrosion engineering applications.

Eco-Friendly Waterborne Polyurethane Coating Modified with Ethylenediamine-Functionalized Graphene Oxide for Enhanced Anticorrosion Performance.

This study explores the potential of graphene oxide (GO) as an additive in waterborne polyurethane (WPU) resins to create eco-friendly coatings with enhanced anticorrosive properties. Traditionally, WPU's hydrophilic nature has limited its use in corrosion-resistant coatings. We investigate the impact of incorporating various GO concentrations (0.01, 0.1, and 1.3 wt%) and functionalizing GO with ethylenediamine (EDA) on the development of anticorrosive coatings for carbon steel. It was observed, by potentiodynamic polarization analysis in a 3.5% NaCl solution, that the low GO content in the WPU matrix significantly improved anticorrosion properties, with the 0.01 wt% GO-EDA formulation showing exceptional performance, high Ecorr (-117.82 mV), low icorr (3.70 × 10-9 A cm-2), and an inhibition corrosion efficiency (η) of 99.60%. Raman imaging mappings revealed that excessive GO content led to agglomeration, creating pathways for corrosive species. In UV/condensation tests, the 0.01 wt% GO-EDA coating exhibited the most promising results, with minimal corrosion products compared to pristine WPU. The large lateral dimensions of GO sheets and the cross-linking facilitated by EDA enhanced the interfacial properties and dispersion within the WPU matrix, resulting in superior barrier properties and anticorrosion performance. This advancement underscores the potential of GO-based coatings for environmentally friendly corrosion protection.

Fabrication of Ni–ZrO2 nanocomposites through a new electroforming bath and Assessment of their morphology, wear, and corrosion resistance

Nowadays, researchers are looking for ways to produce complex tools and pieces with high precision at a low cost. In recent decades, electroforming has been an important and stable technique for producing composite parts. In this research, Ni–ZrO2 nanocomposite foils were fabricated by using a nickel-chloride bath through electroforming, a bath not previously utilized for this purpose. In this study, the effects of ZrO2 concentration and direct current density on the volume percentage of ZrO2 nanoparticles and the grain size of the nickel matrix of foils are also investigated. The sample with 13.65 vol % nanoparticles had the highest volume percentage and the minimum nickel grain size of 516.9 nm, which is almost 46 % smaller than the grain size of pure nickel foil. The wear and corrosion behavior of the foils were examined using a pin-on-disk wear test, potentiodynamic polarization, and impedance spectroscopy analysis. The results showed considerable improvement in the wear and corrosion resistance of the Ni–ZrO2 samples compared to the pure electroformed nickel. The nanocomposites exhibit a lower friction coefficient than pure nickel, with a maximum reduction of 44 %. A composite specimen of Ni–ZrO2 had 2.5 % lower corrosion density and 596 % higher charge transfer resistance compared to pure nickel. It was concluded that the nickel-chloride bath has an excellent potential to produce composite nickel foils with acceptable brightness, satisfactory wear, and corrosion resistance.

Holistic development of rechargeable Metal-CO2-Mars battery chemistry for Mars exploration

The development of metal-CO2 batteries is a promising technology due to their high energy density and, more importantly, their ability to utilize the greenhouse gas carbon dioxide (CO2) as an energy carrier and, therefore, to combat the climate change effects. Furthermore, the metal-CO2 battery can offer great benefits in terms of energy storage and in-situ resource utilization for the interplanetary Mars mission, reducing overall mission cost, weight, and complexity. This work is a novel attempt to realize the feasible development of a metal-CO2Mars battery for Mars exploration. To the best of our knowledge, we hereby report the practical configuration of metal (X)-CO2Mars batteries (X = Li, Na and K) which is operated in a simulated Martian atmosphere for the first time. To develop a better fundamental understanding, we investigate the effective reversibility and discharge-reaction product formation of these metal-CO2Mars batteries. Further, the electrochemical performance and underlying mechanism of metal-CO2Mars batteries are evaluated using electrochemical testing (galvanic discharge-charge, cyclic voltammetry), potentiodynamic polarization, and Raman spectroscopy analysis, which are then later supported by first-principle calculation based on density functional theory. Thus, we believe that this work provide a rational design strategy for the practical development of metal-CO2Mars and metal-CO2 batteries.

Water soluble redox‐active polyurethanes as efficient corrosive inhibitors for mild steel

AbstractThere is a necessity for an eco‐friendly inhibitor technology to safeguard mild steel from corrosion. Redox‐active Oligoanilines, namely diamine‐capped trimer (DCTA) and tetramer (DCTAni) have been synthesized and incorporated into the polyurethane backbone derived from polyethylene glycols (PEG, Mw = 2050, 4000) and toluene diisocyanate (TDI). The four water‐soluble polyurethanes, resulting from PEG, TDI, and DCTA/DCTAni, were denoted as IH‐1, IH‐2, IH‐3, and IH‐4. The corresponding redox‐active polyurethanes were rationally characterized using FTIR, and UV–visible spectroscopies. Scanning electron microscopy (SEM) was employed to investigate the surface morphology. The electrochemical properties of these inhibitors were characterized by cyclic voltammetry (CV). All the inhibitors were studied for their corrosion inhibition efficiency using Tafel potentiodynamic polarization analysis and weight loss methods. These demonstrated high efficacy at a low concentration of 200–300 ppm. The absorptivity of polymers on the mild steel were confirmed by Langmuir adsorption isotherms with a well‐fitting (R2 = 99.9%). The SEM analysis showed the adsorption capacity of inhibitors as protective layers for the mild steel panels. Overall, this work paves the way for innovative ideas for producing more water‐soluble and electrochemically active polymer additives as excellent corrosive inhibitors for mild steel surfaces.

Fabrication and characterization of Zinc-xTitanium alloys by SPS for biodegradable implants: A comparative study on corrosion resistance and biological behavior

This study investigated the fabrication and characterization of two new zinc-titanium-based alloys. The Zn-xTi alloys (x = 4 and 10 wt%) were mechanically alloyed by powder metallurgy for 10 h. The spark plasma sintering (SPS) method shaped the resulting powder. The fabricated samples were evaluated in terms of morphology and structure by XRD, SEM, and microhardness tests. The obtained parts’ corrosion resistance and biological behavior were also examined by potentiodynamic polarization analysis, electrochemical impedance spectroscopy (EIS), and MTT tests. The results showed that alloying increased the hardness compared to pure zinc samples. The corrosion test results indicated higher corrosion resistance of Zn–4Ti alloy than Zn–10Ti alloy. The cell toxicity test, performed indirectly by the extraction process, clearly showed lower toxicity of Zn–4Ti alloy compared to the other alloy. In the extractions with low concentrations (25 % and 12.5 %), no cell toxicity was observed in the Zn–4Ti alloy. This research concludes that the alloy containing 4 wt% titanium can be a suitable candidate for making biodegradable implants.

Effect of plating time on surface morphology and corrosion behavior of electroless Ni-P coating in simulated concrete pore solution

As a protective coating, electroless Ni-P (ENP) coating with various deposit times was fabricated on the carbon steel. The morphology, microstructure, and composition of the ENP coating were investigated via SEM, AFM and XRD. The anti-corrosion capability and protective mechanism of the coating exposed to chloride-contaminated simulated concrete pore solution (CL-SCPS) were evaluated by OCP, potentiodynamic polarization, EIS, and Mott-Schottky analysis. As deposit duration increased, the Ni and P content percentage and compactness of ENP coating increased, but “trenches” appeared. The corrosion behavior of ENP coating was closely related to the thickness and surface morphology. That is to say, the coating with the thin layer and defects could represent low corrosion resistance. Moreover, passivation would occur on the ENP coating in an alkaline environment. The performance of the passive film was also related to the thickness and morphology of the coating. The oxidation products could partially repair the surface “trenches”. The ENP coating with an 80-min deposit duration had the highest corrosion resistance in the short immersion stage. Coating with a 60-min deposit duration represented optimal corrosion resistance and desirable electrochemical stability in the long-term service in aggressive media.

Fabrication of a durable corrosion-resistant superamphiphobic CeO2–TiO2 ceramic nanocomposite coating on AZ31B Mg alloy by plasma electrolyte oxidation

A liquid-repellent and corrosion resistant surface was fabricated on AZ31B Mg alloy by the usage of CeO2 and TiO2 nanoparticles (NPs), plasma electrolyte oxidation (PEO) method, and subsequent surface modification. The whole process included two main steps: a) applying PEO with CeO2–TiO2 NPs on AZ31B and b) decreasing surface energy by using a fluorinating agent. Elements that were present on the surface were investigated by XRD and EDS analyses. Surface morphology and its roughness were scrutinized by FESEM images and AFM tests, respectively. Contact angles (CA) of water and some oils (Ethylene glycerol and Glycerol) on the prepared surface were measured. CAs of water and ethylene glycerol were reported at 175.6° and 151.4°, respectively. Also, the corrosion behavior of the prepared surface was assessed by EIS and potentiodynamic polarization analyses. Results showed that the corrosion rate of the neat AZ31B decreased noticeably from 127.78 to 0.027 mpy for superamphiphobic PEO-NPs AZ31B. The prepared sample showed high mechanical durability, which was scrutinized by water floatation, abrasive with grit SiC paper, adhesive tape peeling, and bending tests. After immersion of the sample in 5 wt% NaCl solution for various hours, results showed that the prepared sample had a noticeable corrosion resistance stability.

Influence of Solution Treatment Process on the Properties of Duplex Stainless Steels: A Comparative Study on Microstructure and Corrosion Properties of UNS S32205 and UNS S32760

The study investigated the effect of the solution treatment process on the corrosion behavior and microstructure of the duplex stainless steel. It was also aimed to reveal this effect comparatively depending on the chemical composition and alloying element content. For this purpose, UNS S32205 and UNS S32760 alloys were treated at 1000 °C, 1020 °C and 1040 °C for an hour. A solution treatment temperature was determined according to Thermo-Calc analysis. The examined samples were characterized by an optical microscope, scanning electron microscope, and XRD analysis. Also, electrochemical impedance spectroscopy and potentiodynamic polarization analyses revealed the corrosion properties of solution-treated samples. Microstructural studies showed that enhanced solution treatment temperature increased ferrite content for both alloys. A lower solution treatment temperature caused the formation of sigma in the microstructure of S32760 alloy. On the other hand, the charge transfer resistance of the passive layer was reduced after solution treatment at 1000 °C and 1020 °C, indicating decreasing corrosion resistance. A higher austenite ratio in S32205 led to pitting, while corrosion resistance improved with higher treatment temperatures. The presence of the sigma phase in S32760 significantly impacted corrosion properties by increasing ion transfer on the surface, leading to reduced corrosion resistance. It was determined that solution treatment at 1040 °C was appropriate for both alloys to achieve the desired microstructure and corrosion properties.

Synthesis and characterization of selenium-polyvinyl alcohol nanoparticles as eco-friendly corrosion inhibitor for carbon steel in 1.0 M H2SO4

Selenium nanoparticles capped with polyvinyl alcohol (Se-PVA NPs) have been synthesized by chemical reduction using ascorbic acid as a reducing agent. The synthesized nanoparticles were characterized using XRD, DLS, zeta potential, FT-IR, and TEM analysis and found to be stable. The solution of Se-PVA NPs was used as a carbon steel corrosion inhibitor in 1.0 M H2SO4. The effect of the presence of Se-PVA NPs in the corrosion medium was studied by potentiodynamic polarization and gravimetric analyses In the presence of Se-PVA NPs with a concentration of 600 ppm at 303 K, corrosion inhibition efficiency values of 92.86 % and 92.3 % were recorded by potentiodynamic polarization and gravimetric analysis methods, respectively. Over the Se-PVA NPs concentration range 100–600 ppm, it was found that increasing the concentration increases the inhibition efficiency, while the temperature has an adverse effect, inhibition efficiency values of 80.0 % was recorded at 323 K for the 600 ppm Se-PVA NPs solution. The potentiodynamic polarization measurements suggested that Se-PVA NPs work as a mixed-type inhibitor. The corrosion inhibition process was confirmed by testing the used specimens’ metal surface using SEM and AFM techniques, which showed that the acidic medium’s negative impact (distortion and roughness) on the carbon steel surface was reduced significantly in the presence of Se-PVA NPs. The inhibitor’s adsorption on the metal surface was studied. It obeys the Langmuir isotherm with a mixed-type adsorption process. The related kinetic and thermodynamic parameters were investigated.

New insights into the mechanism causing the loss of anti-corrosion property of superhydrophobic titanium surfaces

In this paper, we provide new insights into the mechanism causing the loss of anti-corrosion property of superhydrophobic titanium (SHP Ti) during potentiodynamic polarization (PDP) measurements. The water contact angle and sliding angle values of the SHP Ti, produced by a facile two-step process: anodizing and coating, were >160° and 6±2°, respectively. The anodization of Ti resulted in randomly distributed micro-clusters of TiO2-xCly covering the Ti surface homogeneously while the low surface energy organic coatings were inhomogeneous in coverage and specifically distributed over the micro-clusters alone of the anodized titanium surface. The electrochemical impedance (EIS) analysis of the SHP CP-Ti samples has shown more than an order of magnitude improvement in their barrier /polarization resistance (Rp) values at ∼ 100 MΩ.cm2 suggesting the effectiveness of the SHP coatings as a barrier against corrosion in neutral chloride environments. However, the Rp values (∼ 10 M Ω.cm2) of the SHP coatings obtained from the PDP analysis were an order of magnitude lower than the Rp values derived from the EIS. SHP CP-Ti samples showed dual passive range behaviour with an initial narrow passive region due to the porous anodized TiO2-xCly layer while the later stage passivity due to the barrier TiO2 layer, where the outer anodized porous TiO2-xCly layer was less effective against corrosion in neutral chloride media. Detailed analysis showed that in PDP, the sample lost its SHP because of the permeation of electrolyte into the hierarchical surface, due to its sensitivity to polarization, owing to the lower thickness of the organic layers. The mechanism involved in the loss of SHP and the limitation of the PDP technique for the corrosion analysis of SHP / organic coatings on metal surfaces is highlighted.

An investigation on the mechanical and corrosion protection properties of poly(arylene ether nitrile) reinforced epoxy coating

To follow the current industrial demand, epoxy coatings which feature extraordinary comprehensive properties have been considered as a versatile and promising thermosetting resin for application in various middle and high-end sectors of multitudinous industries. Regrettably, epoxy coatings possess the inherent shortcoming of poor durability to external force and deformation, severely restricting further introjection in various fields. Herein, this study employs poly(arylene ether nitrile) with bisphenol A structure (PENBA) as superior intensifying agent to ameliorate the toughness and corrosion resistance of brittle epoxy coatings. As a linear thermoplastic polymer with satisfying mechanical performances, PENBA serves as epoxy's energy-dissipating medium and forms a semi-interpenetrating polymer network (SIPN) with epoxy matrix, efficiently impeding epoxy's fracture and crack propagation. As a result, the tensile strength, elongation at break, impact strength, and flexural strength of PENBA-modified epoxy possess considerable increments of 214 %, 360 %, 148 %, and 295 % in sequence by contrast with the pristine epoxy. Meanwhile, according to the potentiodynamic polarization analysis, the PENBA with outstanding chemical resistance also significantly promoted the epoxy's corrosion resistance, endowing the epoxy coating with the most positive Ecorr and icorr of −0.453 V and 9.439 × 10−10 A/cm2 when PENBA reached 15 % (mass percent) at the end of entire soaking process.

Novel high-performance and cost-effective green inhibitor based on fundamental theoretical evaluations combined with electrochemical/surface examinations of Arachis hypogaea shell extract for pipeline steel corrosion in 1 M H2SO4 solution

Traditional corrosion inhibitors have been frequently used for metal protection against strong acids. However, most of them are hazardous compounds with high costs. Therefore, due to the strict environmentally friendly regulations, green and low-cost compounds from renewable sources have gained high consideration in recent applications. In the present study, the Arachis hypogaea shell extract, commonly called groundnut, a cost-effective was selected to inhibit API X 65 pipeline steel corrosion in 1 mol·L−1 H2SO4 solution. The Arachis hypogaea shell composition was examined by FTIR analysis. The Arachis hypogaea shell on pipeline steel in H2SO4 solutions was studied via gravimetric, potentiodynamic polarization, and surface analysis (SEM and EDX). Electron donor atoms present in the Arachis hypogaea shell extract molecules is responsible for its adsorption on the surface of the metal. Experimental study shows that with increasing Arachis hypogaea shell concentrations, the inhibition tendency increased and reached 98.84% at 4 g L−1 after 24 h. Arachis hypogaea shell extract behaved as mixed-type inhibitor, and the surface coverage fits the Langmuir isotherm, signifying that the steel surface was covered by a monolayer of inhibitor molecules without intermolecular interactions. SEM analysis shows that Arachis hypogaea molecule adsorption on the metal surface reduced considerably its dissolution rate resulting in a smooth and clean surface with few damaged areas. The use of water for extraction of Arachis hypogaea shell exhibiting inhibition efficiency, non-toxic, and cost-effective than other green inhibitors, proposes the Arachis hypogaea shell as an excellent green inhibitor for API X 65 steel corrosion in 1 mol·L−1 H2SO4 solution.