Potentiodynamic Polarization Measurements Research Articles

Fabrication and Properties of Superhydrophobic Colored Stainless Steel Surface for Decoration and Anti-Corrosion

A colored superhydrophobic surface on a stainless steel substrate was achieved by means of high temperature oxidation combined with subsequent spraying modification by superhydrophobic nano-silica film. Comprehensive characterizations of the surface were performed in terms of color, morphology, composition, wettability, and corrosion resistance by optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), contact angle, potentiodynamic polarization, and electrochemical impedance spectroscopy measurement. At 400 °C, the surface was pale yellow, gradually turning yellow and then red as the temperature increased. At 700 °C and 800 °C, the surface colors were blue and dark brown, respectively. The samples with oxide films demonstrated lower contact angles, specifically 80.5° ± 2.5 at 400 °C, 79.1° ± 2.8 at 500 °C, and 75.6° ± 3.4 at 600 °C. The polarization resistance measured on the oxidized film formed at 600 °C exceeded 7.93 × 104 Ω·cm2. After spraying the treatment, these colorful surfaces exhibited superhydrophobicity, they were self-cleaning, and they satisfied anti-corrosion properties. The treatment performs as an excellent barrier and exhibits a high corrosion resistance of 4.68 × 106 Ω·cm2. The successful preparation of superhydrophobic colored surfaces offers the possibility of providing stainless steel with both decoration value and self-cleaning function simultaneously by our proposed chromium-free fabrication process.

Gleditsia sinensic extract as green corrosion inhibitor for N80 steel in 1 M HCl

The inhibition efficiency of gleditsia sinensic extract (GSE) as green corrosion inhibitor for N80 steel has been evaluated by weightlessness test, electrochemical impedance spectroscopy (EIS) study, Potentiodynamic polarization (PDP) measurement and Density Functional Theory (DFT) calculations in 1M HCl solution. Consequently, the inhibition efficiency of GSE is increased with the concentrations, immersion time and corrosion temperature (except 60 °C). After 144 h of immersion at 30 °C, the inhibition efficiency of GSE at a concentration of 500 mg/L was as high as 92.34 %. The adsorption process was spontaneous exothermic and conformed to Langmuir's law of adsorption, while Tafel's analysis showed that GSE is a mixed type of inhibitor. In addition, the corrosion products have been examined by scanning electron microscopy (SEM) analysis, X-Ray Diffractomer (XRD) testing, Fourier transform infrared spectroscopy (FTIR-ATR), UV-Vis spectroscopy and contact angle (CA) measurements. Furthermore, the corrosion inhibition mechanism has also been investigated.

Impact of cooling methods on the corrosion behavior of AA6063 aluminum alloy in a chloride solution

Abstract In this work, the AA6063 Al alloy was processed by cooling at four different conditions. The impact of the type of cooling method on the corrosion behavior of the produced alloys after 1 and 24 h in 3.5% NaCl solutions was carried out. Various electrochemical measurements, such as cyclic potentiodynamic polarization (CPP), chronoamperometric, and electrochemical impedance spectroscopy (EIS) measurements, were employed. The CPP data revealed that the intensity of corrosion of the alloys is highly influenced by the cooling method. The change in the chronoamperometric current at −650 mV (Ag/AgCl) over time indicates the possibility of pitting corrosion, particularly after 24 h, where the recorded currents showed a continuous increase over time. The scanning electron microscopy images taken for the surfaces of the alloys after corrosion confirmed that the lowest deterioration occurring on the surface was for the AA6063 alloy that was quenched in water. The EIS plots also demonstrated that AA6063 alloy exhibits different corrosion resistances when different cooling methods are applied. All measurements indicated that the corrosion resistance increases in the following order: the quenched alloy in water > the air-cooled alloy > the furnace-cooled alloy > the as-received alloy. The exposure for 24 h decreases the corrosion damage of all alloys via the formation and thickening of a top layer of corrosion products on its surface over time.

Aluminum Current Collector Corrosion Inhibition by a Newly Synthesized 5-Formyl-8-Hydroxyquinoline for Aqueous-Based Battery

Aluminum foil is the most frequently used as a cathodic current collector for batteries because of its high electrical conductivity, low cost, robust electrochemical properties, and low density. However, as next-generation batteries are created, serious corrosion poses new challenges to aluminum current collectors, especially with no effective additive in an aqueous electrolyte. A newly 5-formyl-8-hydroxyquinoline (FHQ) additive is designed and synthesized as an effective corrosion inhibitor for aluminum foil. The effect of FHQ on the corrosion of the Al current collector in an aqueous-based electrolyte has been investigated using electrochemical methods and spectroscopy techniques for assessing the corrosion inhibition efficacy and protective film formation on the Al surface. The Potentiodynamic polarization measurements indicated that the corrosion rate in millimeters per year (mmpy) of 1.37×10-3 is much lower in the aqueous electrolyte of 21 m LiTFSI with the FHQ additive than 2.29×10-2 in the electrolyte without an additive. Meanwhile, the Zn//LVPF configuration is developed as an efficient protocol to evaluate the corrosion prevention efficiency of inhibitors in an aqueous-based battery for the first time. The Zn//LVPF cell in the aqueous electrolyte with the FHQ additive provides much higher capacity retention and average Coulombic efficiency than the cell in the electrolyte in the absence of an additive. Interestingly, the Al corrosion prevention efficiency of the developed additive is also observed in an organic electrolyte-based battery. This work paves a new pathway to develop effective Al corrosion inhibitors for applications in lithium-ion batteries, especially in aqueous electrolytes. Keywords; Corrosion inhibitor; 8-hydroxyquinoline; 5-formyl-8-hydroxyquinoline; Doner/acceptor; HOMO-LUMO; Aluminum corrosion.

The effect of tempering temperature on microstructure and corrosion resistance of M390 powder metallurgical martensitic stainless steel

The corrosion resistance of M390 powder metallurgical martensitic stainless steel with different tempering temperatures was investigated by potentiodynamic polarization measurements, salt spray tests, and microstructural analyses utilizing scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The tempering temperature had no significant effect on the size and volume fraction of carbides. The corrosion resistance of M390 steel gradually deteriorated with increasing tempering temperature, and a loss passivation (LOP) effect was observed when tempered at 450 °C, 500 °C, and 550 °C. Transmission electron microscopy (TEM) analysis showed that the width of the Cr-depleted zones around the undissolved M7C3 carbides increased with increasing tempering temperature, while the Cr content in these zones decreased, which was the main reason for the deterioration of corrosion resistance. This study offers valuable insights into optimizing the tempering process to improve the corrosion resistance of M390 steel for practical applications.

One-pot synthesis of N'-(thiophen-2-ylmethylene)isonicotinohydrazide Schiff-base as a corrosion inhibitor for C-steel in 1 M HCl: Theoretical, electrochemical, adsorption and spectroscopic inspections

Although carbon steel (CS) is an essential component utilized in many industries, it regrettably corrodes when exposed to acidic conditions. Schiff bases have recently become more concerned with the corrosion prevention of CS. Hydrazides and the related compounds shown to be effective inhibitors of CS corrosion in acids. These compounds are commonly employed as origins or intermediates to several key molecules in the synthesis of organic compounds, and they are highly sought after due to their wide range of biological and therapeutic applications. They have anti-bacterial, anti-malarial, anti-fungal, and anticancer properties, as well as corrosion protection. Hence, the inhibitory effectiveness of a new synthesized (E)-N'-(thiophen-2-ylmethylene) isonicotinohydrazide (TMNH) Schiff-base for the corrosion of CS in 1 M HCl was explored. The structure of TMNH was validated by FT-IR and 1H NMR spectroscopy. A number of chemical, spectral, and electrochemical techniques such as potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and mass loss (ML) have been used to evaluate its anticorrosion power. PDP measurements showed that it is a mixed-type inhibitor. In addition, EIS measurements showed that Rct increased sharply from 37 without the corrosion inhibitor to 589 Ω cm-2 in the presence of 1 mM TMNH and from PDP scans, the corresponding icorr decreased dramatically from 0.6158 to 0.0314 μA cm-2. ML tests have proven their effectiveness, achieving an inhibitory efficiency of 95.3 %. Adsorption studies were also conducted to determine the nature of the corrosion retardation mechanism. The TMNH inhibitor was spontaneously chemically/physically adsorbed onto the CS surface following the Langmuir isotherm. Statistical calculations were also applied to verify the accuracy of the experimental results. The Monte Carlo model showed that the inhibitory molecules adsorbed flat on only one side, increasing the chances of adsorption.

Walnut (Juglans regia L.) fruit septum alcoholic extract as corrosion inhibitor for Fe B500B steel bars in mixed acidic solution

The corrosion inhibition performance of the walnut fruit (Juglans regia L.) septum alcoholic extract for Fe B500B steel bars in a mixed acidic solution (H2SO4/HCl) is reported. Weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy measurements were performed at 298 to 318 K, with the addition of various extract concentrations. Results showed the maximum corrosion inhibition efficiency of 86.99 % for 300 mg L-1 extract added. The extract acts as a mixed-type inhibitor, predominantly affect­ing the anodic side, following Flory-Huggins adsorption isotherm. Thermodynamic analysis indicated an endothermic process with both chemisorption and physisorption on the steel bar surface. Surface characterization was conducted using ATR-FTIR, UV-vis and SEM techniques to prove the adsorption of the inhibitor molecules on the steel bar surface. Also, a possible adsorption mechanism of inhibitor molecules was proposed.

Revisiting Ag addition in 7xxx aluminum alloys: Insights into its impact on the microstructure and properties of an Al-Zn-Mg-Cu-Zr alloy with a Zn/Mg ratio of 4

In this study, the influence of minor Ag addition on the microstructure, mechanical and corrosion properties of an Al-Zn-Mg-Cu-Zr (7449) alloy with Zn/Mg ratio of 4 was systematically investigated using various materials characterization techniques, Slow Strain Rate Test (SSRT), Potentiodynamic Polarization (PDP) and Intergranular Corrosion (IGC) measurements. Microstructure characterization by Scanning Electron Microscopy (SEM) and Differential Scanning Calorimetry (DSC) showed that Ag partitioning in the eutectic Mg(Zn,Cu,Al)2 phase occurs resulting in an increase in its solvus line. After processing to the T4 condition, Ag was partially in solid solution with the excess forming an Ag-rich AlAgZnMgCu phase. Scanning-Transmission Electron Microscopy (STEM) showed evidence of quench-induced η-Mg(Zn,Cu,Al)2 precipitates at the grain boundaries (GBs) in the T4 condition with ∼3 at.% Ag in the Ag-modified alloy. STEM and Atom Probe Tomography (APT) confirmed that ∼1 at. % Ag was present in both the matrix and GB precipitates in the Ag-modified alloy after T76 aging. Furthermore, the frequently reported decrease in the PFZ width with Ag addition was not observed after T76 aging, with both alloys having a similar PFZ width. Despite higher hardness/strength in the T4 condition with Ag addition, no enhanced age hardening response and alteration of the precipitation kinetics was observed during artificial aging at 121 °C. In fact, Ag addition in a 7xxx alloy with Zn/Mg ratio of 4 was found to be detrimental to mechanical properties, stress corrosion cracking, pitting and IGC resistance after T76 aging, which is attributed to the presence of the Ag-rich AlAgZnMgCu phase.

Effect of multiple laser remelting on microstructure and corrosion resistance of Fe0.5CoCrNi1.5Nb0.68Mo0.3 high entropy alloy coatings

High entropy alloy (HEA) coatings of Fe0.5CoCrNi1.5Nb0.68Mo0.3 was prepared on 304 stainless steel using laser cladding and subsequently remelted multiple times. The effects of multiple thermal cycles on the phase composition, grain size, microstructure evolution, and corrosion resistance of the coatings are thoroughly investigated. The original coating consisted of face-centered cubic (FCC), Laves, and NbC phases, and the phase composition does not change obviously, but the distribution and microstructure of the phase change significantly after multiple remelting. As the number of remelting times increased, the bar-like eutectic structure decreased while the lamellar eutectic structure became more prominent. Laser remelting induced dynamic recrystallization in the coating, resulting in a transformation from columnar grains to equiaxed grains, and then back to columnar grains. The grain size also changes significantly with different remelting times. Potentiodynamic polarization and electrochemical impact spectroscopy measurements were conducted in a 3.5 wt% NaCl solution to evaluate the corrosion resistance of the coating. The results revealed both the original coating and the once-remelted coating exhibited lower corrosion current density and higher corrosion potential, but the latter had a higher Faraday impedance. Additionally, immersion tests were performed in 10 wt% FeCl3 solution, which demonstrated that the once-remelted coating displayed fine and uniform corrosion pits with shallow depth. This study provides theoretical support for the regulation of microstructure and the optimization of coating performance. Furthermore, the microstructure evolution law discovered in this research is also applicable to additive manufacturing.

Electroactive additives into polyurethanes for high corrosion resistance coatings for mild steel

AbstractThere is a demand for innovative coatings such as polyurethane (PU) in industrial and commercial sectors to effectively combat corrosion on mild steel substrates. In this work, novel redox‐active polyurea (PUr) additives such as PUr‐diamine capped trimer (DCTA) and PUr‐diamine‐capped tetraaniline (DCTAni), derived from DCTA and DCTAni, were synthesized to enhance the anticorrosion properties of PU coatings. These are characterized using 1H nuclear magnetic resonance spectroscopy, Fourier transformed infrared, and high‐resolution mass spectrometry technical methods. These additives (2, 5, and 10 wt%) were dispersed in a polyurethane‐urea (PUU) matrix, which was synthesized from PTMG‐2000, and IPDI with dihydrazide adipate as a chain extender. The electroactivity of the coatings were evaluated using cyclic voltammetry (CV) and ultraviolet–visible spectroscopy. Furthermore, anticorrosion performance was assessed through electrochemical impedance spectroscopy and Tafel potentiodynamic polarization measurements. The optimal corrosion protection was achieved with increasing weight percent (wt%) of additive in PUU, showing a trend of 10% > 5% > 2%. Coatings reported maximum polarization resistance (Rp) of 122.15 MΩ, with corrosion rates (CR) as low as 2.38 × 10−6 mm/year. Accelerated salt spray testing over 600 h in a 5 wt% NaCl salt fog confirmed the coatings' durability. The microstructures of PUr particles were determined through FESEM characterization. Additive‐blended PUUs exhibited moderate tensile strength and elongation at break compared to the reference PUU matrix. The hydrophobicity of both the reference sample (PUU) and the additive‐blended coatings was measured, with the highest recorded value being at 93.1 ± 0.048 for 10 wt%. Thermal gravimetric analysis demonstrated polymer degradation with a maximum of T5% observed at 304.1°C.

Microstructure, Mechanical, and Corrosion Performance of AA4343/AA3003/AA4343 Laminated Sheets Subjected to Cryorolling and Annealing

The effects of cryorolling (CR), hot rolling (HR), and different annealing temperatures on the microstructure, mechanical, and corrosion performance of AA4343/AA3003/AA4343 laminated sheets are studied. Compared with the HR samples, the microstructure of the CR samples presents a significant decrease in the size of elongated grains and significantly large second‐phase particles Al(Mn, Fe)Si in the AA3003 alloy. Grains in CR samples subjected annealing at 200–300 °C become finer. Increasing to 400–550 °C, the grains begin to grow, and the Si is diffused into the core layer. A comparison of HR and CR processing reveals a significant increase in the yield strength from 153 to 209 MPa and the ultimate tensile strength from 168 MPa to 217 MPa of the laminated sheet. Potentiodynamic polarization measurements and immersion tests are conducted to assess the corrosion morphology. After being immersed in a 3.5% NaCl solution for two weeks, the clad surface of the laminated sheet exhibits uniform corrosion products and pitting corrosion, which shows the pitting corrosion depth of the CR sample improved compared to the HR sample. The study suggests that both CR and annealing can be useful for enhancing the mechanical properties, and corrosion morphology of laminated sheets.

Protection of mild steel from corrosion in HCl solution via green Rumex acetosella extract: Experimental and theoretical studies

The efficiency and potential of green Rumex acetosella extract (RAE) on the inhibition of the mild steel (MS) corrosion were investigated in the acidic environment. The high inhibitive capability of RAE on the mild steel was studied by electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques. In addition, potentiodynamic (PD) polarization measurements were carried out to examine corrosion mechanism. The achieved electrochemical tests showed that RAE has a significant inhibition effect on mild steel corrosion. The results of surface analysis recorded by scanning electron microscopy (SEM), and atomic force microscopy (AFM) depicted that RAE provide strong protective layer on the steel surface via adsorptive groups. The inhibition efficiency was calculated as 99.7 %, and 99.6 % from LPR and EIS after 120 h exposure time. Adsorption free energy (∆Gadso) value is found as −29.79 kJ mol−1, indicating that both physical and chemical adsorptions occur. Furthermore, the obtained experimental findings were supported with quantum chemical calculation results.

Generation of a lignin-polyester coating for the corrosion protection of steel surfaces applied by atmospheric plasma spraying

The natural process of metal corrosion causes significant losses in a wide range of industries, requiring substantial efforts to contain its effects. An alternative approach to corrosion protection is the use of renewable organic coating materials. This research proposes the use of lignin-polyester blends as coating materials. Due to the abundance of functional groups in the lignin structure, it can act as corrosion inhibition centers in the coating. The coatings are deposited on stainless steel surfaces by a novel process route via atmospheric plasma powder spraying (APPS). To determine the effect of the lignin content on the corrosion performance, the specific amounts of lignin and polyester have been varied in 10 % increments from 0 % to 100 % with constant coating parameters. The as-produced coatings exhibited thicknesses that ranged from 11 μm to 30 μm, respectively for the pure lignin and polyester coatings. Additionally, scanning electron microscopy (SEM) analysis demonstrated the meltability of the lignin and polyester powder through the plasma process. Coatings containing a greater proportion of polyester exhibited superior meltability and better coverage. Furthermore, it was observed that the APPS promoted cross-linking of the lignin particles, as determined by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). This, in conjunction with well-balanced lignin-polyester ratios, was instrumental in achieving advanced corrosion resistance as evidenced by Potentiodynamic polarization measurement (PDP). The lignin proportion between 40 % and 60 % produced the highest corrosion inhibition efficiency, with a maximum inhibition of 96 %. Furthermore, pull-off adhesion tests suggest that lignin contributes to the overall cohesive strength of the blend.

Facile fabrication of a flower-like superhydrophobic copper surface with superior corrosion resistance

Abstract A superhydrophobic copper coating was prepared by combining ionic liquid copper electrodeposition and a brief stearic acid modification process. After modification, the copper stearic acid was well formed and flower-like clusters were present on the surface of the superhydrophobic coating. Finally, the surface of the sample exhibits a good superhydrophobic performance with a contact angle of 158° and obvious self-cleaning behavior. The results of potentiodynamic polarization and electrochemical impedance measurements revealed that the presence of a superhydrophobic surface could improve the anti-corrosion property of the samples.

Evaluation of the Potential of Daucus crinitus Extracts and Their Synthesized ZnO Nanoparticles in Inhibiting the Corrosion of Carbon Steel

This study explores Daucus crinitus extracts (DCE) and zinc oxide nanoparticles (ZnO-NPs) synthesized using the extracts as corrosion inhibitors for carbon steel (CS) in HCl medium. The synthesized ZnO-NPs were characterized via UV-vis spectroscopy, exhibiting a peak at approximately 375 nm. The study employed weight loss (WL) and electrochemical measurements, alongside spectrophotometric evaluation of corrosion products. Surface morphology was assessed via scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). Thermodynamic analysis revealed the physical adsorption of DCE on CS according to the Freundlich adsorption isotherm. Potentiodynamic polarization (PP) measurements indicated DCE as a mixed-type corrosion inhibitor. Electrochemical impedance spectroscopy (EIS) exhibited increased charge transfer resistance and reduced double-layer capacitance with inhibitory addition. The most effective inhibition was observed with butanol extract (BE) and improved more with its corresponding nanoparticles (BENPs), exhibiting inhibitory efficiencies of 80.20% and 91.20%, respectively, at 298 K with a concentration of 800 ppm. The evaluation of corrosion products using colorimetry revealed that the concentration of polyphenols decreased after the inhibitory process. Furthermore, the intensity of ferrous ions (Fe2+) decreased as the inhibitory concentration increased. In addition, SEM-EDS analysis confirmed the presence of ZnO-NPs, which enhanced the surface morphology and established a protective layer formed by the adsorbed inhibitors. The SEM-EDS analysis confirmed the presence of ZnO-NPs, the enhancement of surface morphology, and the establishment of a protective layer formed by the adsorbed inhibitors.

Quantum Chemical and Electrochemical Studies of Water and Ethanol Extracts of Salvadora Persica (Miswak) as a New Green Inhibitor for Dental Amalgam in Artificial Saliva

Abstract The corrosion-inhibitive properties of Salvadora Persica water and ethanol extracts as a novel green inhibitor for dental amalgam in artificial saliva were studied by using potentiodynamic polarization measurements and electrochemical impedance spectroscopy measurements (EIS). The electrochemical results revealed that the Salvadora Persica extracts demonstrated strong inhibitory effects at 0.66 g/L and implied that the water extract was more effective than the ethanol extract. The inhibition efficiency (IE%) increases with increasing concentrations of both Salvadora Persica extracts and decreases with increasing temperature. The results of this work indicated that Salvadora Persica extracts act as mixed-type inhibitors, inhibiting the corrosion of dental amalgam by the adsorption process, which followed the Langmuir adsorption isotherm model. The thermodynamic results revealed that the adsorption process is endothermic with electrostatic interaction (physisorption). Various DFT parameters, like HOMO and LUMO energy, gab energy (∆E), electronegativity (χ), softness (

Bio-based ionic liquid as a corrosion inhibitor for mild steel in 5% HCl solution: Experimental and theoretical investigation

In pickling conditions, corrosion inhibitors are commonly used to mitigate the corrosive effects of the acidic environment on metal surfaces. Green corrosion inhibitors are substances that provide corrosion protection while being environmentally friendly, often derived from renewable resources or having minimal environmental impact. Ionic liquids are a class of green corrosion inhibitors that have gained attention for their potential in corrosion protection due to their unique properties. In this study, we synthesized a bio-based choline hexanoate ionic liquid (referred to as ChH) and used FT-IR and 1H NMR spectroscopy to elucidate its structure. Further the effectiveness of ChH IL was examined in preventing MS corrosion in 5% HCl at 20–80 °C. The corrosion behavior of MS was examined using weight loss, potentiodynamic polarization, and EIS measurements. Increasing inhibitor concentration and temperatures improved the inhibition performance. The highest efficiency i.e., 98.16% was observed at 3.3 × 10−3 M of ChH at 60 °C. To verify the adsorption of ChH on the MS further investigations were done using FT-IR, Raman, and XPS analysis.

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.

Electrochemical characteristics of nano-structure TiCN coatings on the tool steel deposited by PACVD in various solutions

This study investigates The electrochemical behavior of various nano-structure TiCN coatings prepared using a plasma-assisted chemical vapor deposition technique in acidic and alkaline solutions. The N2/Ar ratio was varied to explore its effect on the microstructure and electrochemical properties of coatings on the steel cold-work tool. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP) measurements were carried out in various corrosive solutions. Field emission scanning electron microscopy and X-ray diffraction were also utilized to evaluate the microstructure and phase detection. The EIS results showed that the resistance of TiCN coatings increased by about 94.3 % based on the equiaxed structure and small size of the coating cluster in 3.5 % wt NaCl solution after 24 h. The lowest corrosion rate with a value of 5.9 µA cm−2 in Ringer's solution at 37 °C after 24 h was attributed to the TiCN coating with the N2/Ar ratio of 0.4 according to exhibiting the highest Ti content and changes in present phases. The N2/Ar ratio of 0.7 effectively increased the impedance resistance to 97.5 % based on PP test results in 3 M H2SO4 solution. This behavior was related to the lowest value of the C/N ratio and the highest coating thickness.

Pyridazine derivatives as effective anti-corrosion additives for carbon steel in 1 M HCl: Electrochemical, surface and theoretical studies

The study aimed to investigate the corrosion inhibition performance of two new pyridazine derivatives namely ((E)-2-(3-(4-(carboxymethoxy)-3-methoxystyryl)-5-(2-chlorobenzyl)-6-oxopyridazin-1(6H)-yl)acetic acid (CO6) and (E)-6-(4-hydroxy-3-methoxystyryl)pyridazin-3(2H)-one (CO39) for carbon steel (C.S) in 1M HCl by combining electrochemical techniques, surface analysis and theoretical studies. The electrochemical impedance spectroscopy (EIS) data indicated that the inhibitory efficiencies of CO6 and CO39 increased with increasing inhibitor concentration but decreased with increasing temperature, achieving 97.0 % and 95.3 %, respectively. The results of the potentiodynamic polarization (PDP) measurements show that the two pyridazine derivatives acted as mixed inhibitors. In addition, experimental studies have shown that CO6 and CO39 reduce corrosion rates by adsorbing on the steel surface following Langmuir adsorption isotherms. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) indicated that a protective layer had been developed on the surface of the carbon steel, which prevented corrosion from progressing. Quantum chemical computations and the molecular structures of the inhibitors were employed to investigate the mechanism of inhibition. The adsorption of the compounds investigated on C.S was validated by theoretical calculations including density functional theory (DFT) and molecular dynamics simulation (MDS).