Potentiodynamic Polarization Analysis Research Articles

Investigation of the corrosion inhibition performance of snail slime on the exposed surface of mild steel in acidic environment

Corrosion of metals is a major issue in various industries and the use of organic materials, especially plant extracts, as alternatives to toxic chemicals in corrosion inhibitors is gaining attention. However, the potential of animal products as corrosion inhibitors has not been fully explored. This study investigates the corrosion inhibiting potential of snail slime (SS) for mild steel in 0.5 M H2SO4 solution using Gravimetric and electrochemical methods, including open circuit potential (OCP), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS). Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used for material characterization. The results indicate that snail slime has a high inhibition efficiency of up to 92.75%, with inhibition efficiency decreasing as temperature and immersion time increase but it increased with higher inhibitor concentrations. Adsorption studies showed that snail slime exhibited strong adherence to the Langmuir and Temkin adsorption isotherms, indicating spontaneous adsorption on mild steel. The inhibition mechanism shows typical physical adsorption and follows first-order kinetics. While the EIS analysis indicated a charge transfer-controlled corrosion process with the highest inhibition efficiency of 81.74%, the PDP analysis revealed that snail slime acted as a mixed-type inhibitor with the highest inhibition efficiency of 81.98%. FTIR reveals the functional groups responsible for the inhibition exhibited by snail slime inhibitors, including CH, OH, CO-O, CCl, and NH. SEM shows that the inhibition of corrosion is due to the formation of an insoluble stable protective film on the sample surface by an adsorption process. These findings suggest that snail slime has significant potential as an eco-friendly alternative to synthetic corrosion inhibitors in industrial applications.

Electrochemical investigation of the corrosion susceptibility of hybrid reinforced Al6063 with SiC and PKSA in 1.0 M sulfuric acid environment

AbstractThe recycling of agro‐waste as complementary reinforcements has received significant recognition in the development of aluminium matrix composites. Hence, this study examines the corrosion behavior of Al6063 reinforced with hybrid SiC/PKSA (palm kernel shell ash) particles. Through various ratios of SiC and PKSA particles in Al6063 alloy, composites were fabricated by double stir casting. Samples were cut and metallographically prepared for 1 M H2SO4 solution corrosion experiments. Gravimetric, potentiodynamic polarization and electrochemical impedance spectroscopic analyses were employed. The composites corroded initially at relatively high rates, gradually declining during long immersion times in the acidic solution. The intersection of reinforcements at the general surfaces of the composites where flawed oxide skins predominate acted as active sites for corrosion initiation. From potentiodynamic polarization studies, the corrosion currents increased with time for all specimens, with A9 being 1075.65 μA/cm2 at 72 h as against 857.99 μA/cm2 at 24 h of measurement. The corrosion potentials for all the specimens hovered around −654.00 to −647.22 mV. Bode plots revealed similar electrochemical reactions over all the substrates' surfaces. The relative corrosion resistance by the specimen depends on the oxide films' nature as the cathodic interfacial reinforcements dropped off into the acidic environment.

Electrochemical study of aluminum–cubic boron nitride composites synthesized via spark plasma sintering for engineering applications

Herein, aluminum−cubic boron nitride (Al−BN) composites with different reinforcement sizes (20, 40, and 60 µm) were developed via spark plasma sintering while maintaining a constant weight percentage (10 wt%; reinforcement). The powder materials were sintered at a temperature of 550 °C and constant uniaxial pressure of 50 MPa with a heating rate of 100 °C/min. Field-emission scanning electron microscopy analysis of the developed composites revealed a uniform dispersion in the Al matrix. X-ray diffraction analysis indicated the presence of aluminum and cubic boron nitride major and minor phases, respectively. Evidence of chemical reactions and the presence of an interfacial phase were not observed at 550 °C in the Al−cBN composite. The mechanical and electrochemical properties of the composites were investigated as a function of the cBN particle size. The results demonstrated that the composite with a cBN particle size of 20 µm (i.e., more particles in the Al matrix than other compositions) strengthens the matrix owing to the better stress drive in the matrix and exhibits the highest average hardness (1.78 GPa), elastic modulus (76.1 GPa), and percentage of densification (98.1%) compared to the other tested composites. The corrosion behavior and resistance against pitting corrosion of pure Al and cBN-based composites were investigated in a 3.5 wt% NaCl solution using electrochemical techniques, such as open circuit potential, electrochemical impedance spectroscopy, and cyclic potentiodynamic polarization analyses. Electrochemical studies revealed that among the analyzed samples, the composite with 20 µm cBN particles exhibits an excellent polarization resistance, in addition to the lowest corrosion rate (∼5 mills per year) and a very high resistance to pit formation in a corrosive environment.

Construction, Characterization, DFT Computational Study, and Evaluation the Performance of Some New N-Amino Pyridinone Schiff Base Catalyzed with Ceric(IV) Ammonium Nitrate (CAN) as Corrosion Inhibitors in Some Petroleum Applications

In this paper, two novel organic inhibitors, TAP-TPP and TAP-CEQ, were prepared via Schiff base condensation as a green chemistry methodology using an eco-friendly catalyst, ceric ammonium nitrate, with a high yield (87% and 91%), and characterized via elemental analysis, FTIR, 1H, and 13C NMR spectroscopic analysis tools. Weight loss assessment was utilized as a chemical testing method, and the maximum inhibition efficiency of TAP-TPP and TAP-CEQ is 89.4% and 91.8%, respectively. PDP and EIS were electrochemical measures to determine the efficacy of both inhibitors as anticorrosion for carbon steel alloys in 2 M HCl aggressive media. The collected electrochemical results demonstrated that both inhibitors behaved as excellent anticorrosion agents for metallic constructions. According to the potentiodynamic polarization (PDP) analysis, these organic inhibitors worked as mixed-type inhibitors. The adsorption isotherm revealed that undertaken compounds obeyed Langmuir adsorption isotherm with the free energies of adsorption of ranged from ΔG = − 34.29 to − 34.63 kJ Mol−1. Also, electrochemical impedance spectroscopy (EIS) data confirmed that the values charge transfer resistance (Rct) was increased by increasing the concentration of the injected inhibitor molecules. In contrast, the electrochemical double layer (Cdl) was dramatically decreased. The work was supported by two-surface analysis methods such as SEM and EDX. For more details, the values of percentage inhibition efficiency can be ordered as follows: TAP-CEQ > TAP-TPP. Finally, a suitable inhibition mechanism and theoretical studies including EHOMO, ELUMO, diploe moment (µ), and electrophilicity index (ω) were assumed and discussed in detailed.

Effect of NH4Cl on the rusting leaching behavior of metallic phase of iron in reduced ilmenite during TiO2 purification: An electrochemical and density-functional theory study

Ilmenite is the primary feedstock for the manufacturing of titanium goods, however it needs to be refined before the usage. Becher is an eco-friendly process for refining ilmenite by rusting metallic iron from reduced ilmenite to separate iron and TiO2, and NH4Cl is the commonly utilized solvent in this method. In the current study, the contribution of NH4Cl was investigated by comparative analysis of the rusting leaching behavior of iron in the Becher process environment, and the solvents including NH4Cl, CH3COONH4, NaCl and CH3COONa were selected. Electrochemical measurements including potentiodynamic polarization analysis, electrochemical impedance spectroscopy as well as surface morphology analysis utilizing scanning electron microscopy and atomic force microscopy were performed. The obtained results indicate that NH4Cl has the highest rusting rate, with NH3 playing the most important role than Cl−. The presence of ammonia prevents the formation of an oxide film on the iron surface. The DFT calculation reveals the NH3 adsorption on the Fe surface enhances Fe susceptibility to electron loss, consistent with the experimental observation of NH3-accelerated iron corrosion. The obtained understanding and methodology sheds lights on the mechanism of NH4Cl action and offers new insights for the study of rusting leaching catalysts.

Synthesis, Characterization, Antibacterial, Antifungal and Anticorrosion Activities of 1,2,4-Triazolo[1,5-a]quinazolinone.

The synthesis of 5,6,7,8-tetrahydro-[1,2,4]triazolo[5,1-b]quinazolin-9(4H)-one (THTQ), a potentially biologically active compound, was pursued, and its structure was determined through a sequence of spectral analysis, including 1H-NMR, 13C-NMR, IR, and HRMS. Four bacterial and four fungal strains were evaluated for their susceptibility to the antibacterial and antifungal properties of the THTQ compound using the well diffusion method. The impact of THTQ on the corrosion of mild steel in a 1 M HCl solution was evaluated using various methods such as weight loss, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) analysis. The study revealed that the effectiveness of THTQ as an inhibitor increased with the concentration but decreased with temperature. The PDP analysis suggested that THTQ acted as a mixed-type inhibitor, whereas the EIS data showed that it created a protective layer on the steel surface. This protective layer occurs due to the adsorption behavior of THTQ following Langmuir's adsorption isotherm. The inhibition potential of THTQ is also predicted theoretically using DFT at B3LYP and Monte Carlo simulation.

Effective corrosion inhibition of mild steel using novel 1,3,4-oxadiazole-pyridine hybrids: Synthesis, electrochemical, morphological, and computational insights

An easy synthesis of two 1,3,4-oxadiazole derivatives, namely, 2-phenyl-5-(pyridin-3-yl)-1,3,4-oxadiazole (POX) and 2-(4-methoxyphenyl)-5-(pyridin-3-yl)-1,3,4-oxadiazole (4-PMOX), and their corrosion-inhibition efficacy against mild steel corrosion in 1 N HCl, is evaluated using weight loss from 303 to 323 K, Electrochemical Impedance Spectroscopy (EIS), Potentiodynamic Polarization (PDP), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), UV–Vis spectroscopy, along with theoretical evaluation. Both POX and 4-PMOX exhibit excellent inhibition efficiency, with values reaching 97.83% and 98% at 500 ppm, respectively. The PDP analysis reveals that both derivatives act as mixed-type inhibitors. The Langmuir adsorption isotherm provides insights into the adsorption phenomena, demonstrating that 4-PMOX exhibits superior adsorption behavior on the mild steel surface compared to POX. This finding is further supported by SEM, DFT, RDF, and MSD analyses. Quantum mechanical parameters, including EHOMO, ELUMO, dipole moment (μ), energy gap (ΔE), etc., are in good agreement with the effectiveness of inhibition performance revealing ΔE values of 3.10 and 2.75 for POX and 4-PMOX, respectively. The results obtained from this study hold significant implications for researchers aiming to design more efficient organic inhibitors to combat metal corrosion.

Fabrication of TiO2 nanotubes with effect of water and in‐situ condition for biomedical application

AbstractSynthesis of TiO2 nanotubes on titanium alloys for environmental and energy applications are highly encouraged by medical industries. Formation of nanotubes on titanium material delivers superior properties in the view of phase transformation, surface morphological, nanomechanical properties, and corrosion resistances. In this research work, synthesis of TiO2 nanotubes under 8 and 12 Vol. % of water content with in‐situ voltage condition. The fabricated nanotubes surface morphology was analyzed with the use of HR‐Sem. The formation of nanotubes surface has been identified with composite faces of smooth and rough (length of 1.6 and 1.8 μm) by the effect of water content and voltage variations. The nanomechanical properties were analyzed with nanoindentation Pmax received as max of 265 and min of 248 μN. Nanotubes strength depends on the nanotubes length. Potentiodynamic polarization analysis indicated that combination of smooth and rough surfaces was highly encouraging the corrosion resistances.

Insights into the Response Differences of Ultrasonic Rolled A3 Carbon Steels and 316L Stainless Steels to Scale and Wax Precipitation Behavior

AbstractIn this work, the antiscaling and antiwaxing properties are evaluated by surface roughness testing, water contact angle measurements, scale and wax deposition testing, and potentiodynamic polarization analysis, respectively. The morphologies and microstructures of the samples before and after ultrasonic surface rolling process (USRP) are analyzed by scanning electron microscopy and optical microscopy, respectively. The results show that for 316L stainless steel after USRP, its surface roughness and surface energy decrease by 97% and 27%, respectively, and the average scale amount is decreased by 73% and antiwaxing rate is up to 63%. In contrast, for the A3 steel after USRP, the average amount of scale and wax deposition increases due to the enhanced atomic activity of the surface layer and surface energy although its reduced surface roughness. It is found that the lower surface energy is the primary factor for improving the antiscaling and antiwaxing performance. A second factor may be related to the smooth surface and superior corrosion resistance.

Experimental and theoretical studies on the inhibitory potential of Lippia javanica leaf extract for aluminium corrosion in 1M HCl medium

Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and gravimetric analysis techniques were used to evaluate the ability of Lippia javanica leaf extract to inhibit aluminium (Al) corrosion in 1 M HCl solution. The formation of the protective film was confirmed using Ultraviolet-visible spectroscopy (UV–Vis), Fourier transform-infrared spectroscopy (FTIR) and contact angle studies. According to EIS, the presence of L. javanica extract in the acidic solution decreased the corrosion current density (icorr) and the double-layer capacitance (Cdl) due to the formation of a protective adsorption layer on the Al surface. PDP curves revealed anodic polarization passivation of the Al substrate, a well-known property of a highly entropic alloy like Al. Gravimetric results showed that the maximum protective efficacy of the L. javanica extract was 91.89% when the optimal concentration of the extract was 800 ppm. The contact angle increased to 123° in the presence of ALJPE, indicating the hydrophobic nature of the Al surface due to the formation of a protective film. The FTIR spectra revealed the involvement of C=O, C=C, O–H, =C–O–C, S=O, and C–H during the adsorption process, leading to the formation of ALJPE–Al3+ protective complexes. It was discovered that the adsorption mechanism of the extract on the Al surface follows the Langmuir adsorption isotherm description process. Using density functional theory (DFT), different dsorption positions were studied, finding that verbascoside preferentially binds to the Al(111) surface via the phenylethanoid group, with the oxygen atom close to the Al surface, leading to a binding energy of 114.620 kcal/mol.

Corrosion inhibiting properties of polysaccharide extracted from Lepidium meyenii root for mild steel in acidic medium: Experimental, density functional theory, and Monte Carlo simulation studies

A polysaccharide obtained from maca (Lepidium meyenii) root extract (MREP) was evaluated as a novel, inexpensive, biocompatible corrosion inhibitor for mild steel (MS) in 1 M HCl. Fourier transform infrared (FTIR) and nuclear magnetic resonance studies were conducted to characterize the inhibitor. Gravimetric, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) techniques were applied to assess the corrosion inhibition potential of the inhibitor. Gravimetric studies were conducted over the temperature range of 30–60 °C. The inhibition efficiency of MREP increased with the concentration and temperature. The maximum inhibition efficiency of MREP was 94.78% at 700 ppm and 60 °C. EIS analysis showed that as the MREP concentration increased, the Rp value obtained from the Nyquist plot increased due to the formation of MREP barrier film at the MS/solution interface. PDP analysis showed that MREP had a mixed type inhibition mechanism. The inhibition efficiencies calculated based on gravimetric, EIS, and PDP analyses were similar. Ultraviolet–visible, FTIR, X-ray photoelectron spectroscopy, atomic force microscopy, and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDAX) analyses demonstrated the formation of a protective film on the MS surface. MREP adsorbed on MS according to the Langmuir adsorption isotherm. The calculated density functional theory parameters indicated the formation of a strong bond between MREP and the unoccupied d-orbital of iron atoms in MS. By contrast, Monte Carlo simulations indicated the adsorption of the MREP inhibitor on the MS surface at the atomic level.

Corrosion resistance of austenitic stainless steel using cathodic plasma electrolytic oxidation

Substantial improvement of corrosion resistance of austenitic stainless steel (SS) has been demonstrated with a protective oxide layer formed by the cathodic plasma electrolytic oxidation (CPEO) process. Two distinct layers, a porous-structured outer layer comprising Fe oxides and a compact inner layer comprising Cr oxides, were created on the SS surface after the CPEO process. The thicknesses of the outer and inner layers were approximately 7 μm and 12 μm, respectively, and the oxide layers were fabricated in an exceptionally short time of <30 s. A potentiodynamic polarization analysis exhibited a 65 % decrease in the corrosion current after the formation of the protective oxide layer, verifying the effectiveness of the CPEO treatment on the corrosion resistance of SS. An electrochemical impedance spectroscopy study revealed that the outer layer captured corrosive species due to its porous structure, while the inner layer had high resistance to reactions with corrosive species due to the compact structure of Cr oxides. Additionally, a Rockwell C indentation test demonstrated the robust mechanical property of the protective oxide layer with a strong bonding strength to the substrate.

Electrochemical and in vitro biological behaviors of a Ti-Mo-Fe alloy specifically designed for stent applications

There is a deep interest in developing new Ni-free Ti-based alloys to replace 316 L stainless steel and Co-Cr alloys for endovascular stent application, mainly because the release of Ni can generate toxicity and allergenicity. Interactions of Ti alloy biomaterials with bone cells and tissues have been widely investigated and reported, while interactions with vascular cells and tissues, such as endothelial cells (ECs) and smooth muscle cells (SMCs), are scarce. Therefore, this study focused on the relationship among the surface finishing features, corrosion behavior and in vitro biological performances regarding human ECs, SMCs and blood of a newly developed Ti-8Mo-2Fe (TMF) alloy, specifically designed for balloon-expandable stent applications. The alloy performances were compared to those of 316 L and pure Ti, prepared with the same surface finishing techniques, which are mechanical polishing and electropolishing. Surface properties were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle (CA) and x-ray photoelectron spectroscopy (XPS). The corrosion behavior was assessed with potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) tests in phosphate buffered saline (PBS) solution. No significant differences were observed regarding the corrosion rate measured with PDP analyses, which was of the order of 2 × 10−4 mm/y for all the studied materials. Moreover, similarly to pure Ti, TMF exhibited an advantage over 316 L for biomedical applications, namely remarkable resistance to pitting corrosion up to high potentials. The results evidenced a good cytocompatibility and hemocompatibility, making this group of alloy a potential candidate for cardiovascular implants. In fact, both ECs and SMCs proliferated on TMF surfaces showing a 7-day viability similar to that of pure Ti. Regarding hemocompatibility, TMF did not cause hemolysis, and blood coagulation was delayed on its surface in comparison to pure Ti. When compared to 316 L, TMF showed similar hemocompatibility.

Corrosion Inhibition Behavior and Adsorption Mechanism of Ethyl Acetate Extract from Scorzonera Undulata for Carbon Steel in 1 M HCl Solution.

For carbon steel X70 in a 1 M hydrochloric acid solution, Scorzonera undulata acetate extract (SUAc) was investigated as an ecological corrosion inhibitor. The anti-corrosion effect of Scorzonera undulata extract is studied using potentiodynamic polarization analysis and electrochemical impedance spectroscopy (EIS). The polarization curves clearly show that the extract is an excellent mixed inhibitor. Our findings show that the maximum inhibition efficiency of 83% has been found with inhibitor concentration up to 400 mg/L at 298 Kelvin. The Langmuir isotherm is followed by the inhibitor's adsorption on the steel surface and physical adsorption was discovered to be the mechanism. To understand the inhibitory mechanism, thermodynamic parameters (∆G°ads) and activation parameters (Ea, ∆Ha, and ∆Sa) were determined. Scanning electron microscopy (SEM) and X-ray photoelectron spectrometry studies of the surface chemistry and morphology are included to this investigation. The results obtained from chemical and electrochemical measurements, confirm that a protective film is formed on the carbon steel surface.

Understanding microstructure evolution and corrosion behavior of wire arc cladding inconel 625 Superalloy by thermodynamic approaches

Ni-based superalloys have excellent corrosion and oxidation resistance and are often used to make coatings on engineering components or steel materials. The free energy of the melt of Inconel 625 and multiple mixed Ni-based alloy were calculated by the optimized molecular interaction volume model (MIVM), and the cladding material composition is designed according to the composition - free energy curve. The corrosion resistance of the single and double deposited Ni-based layers with different Fe content were studied and compared. Potentiodynamic polarization and electrochemical impedance spectroscopy(EIS) analyses show that the corrosion resistance of the single deposited layers increases with the increase of Fe element, which Component is designed by thermodynamic calculation. Because of the thermodynamic stability of alloy melt is improved by the increase of Fe element, and reducing element segregation and formation of Laves phase. The pitting potential of the single deposited layer increase with the increase of Fe content, and the passivation film of the double deposited layers are more stable.

Investigation into the adsorption and inhibition properties of sodium octanoate against CO2 corrosion of C1018 carbon steel under static and hydrodynamic conditions

Sodium octanoate (Na-oct), a simple, naturally-abundant, cheap and low-toxic organic molecule has been investigated for its adsorption and inhibition properties against the CO2 corrosion of C1018 carbon steel in 3.5 % NaCl under static (0 rpm) and hydrodynamic conditions (1000 rpm). At open circuit potential (OCP) under static condition, a Langmuir-type adsorption of Na-oct modified the dielectric property of the steel-solution interface by lowering double layer capacitance and increasing resistance to charge transfer, based on electrochemical impedance spectroscopy (EIS) analysis. Under this condition, potentiodynamic polarization (PDP) analysis showed that Na-oct adsorbed more preferentially on anodic sites of steel surface and impacted ∼96 % inhibition efficiency. Hydrodynamic condition at 1000 rpm caused a Langmuir and Temkin adsorption mechanism and diminished the Na-oct efficiency to ∼86 %. FTIR characterization revealed that the inhibitor adsorption was enabled by its COO– functional group. Computational modeling, using DFT and MDS, confirmed the experimental findings.

THE EFFECT OF ADDITION GREEN INHIBITOR D-GALACTOSE ON CORROSION RATE OF ALUMINUM ALLOY 5052 IN SULFURIC ACID (H2SO4) MEDIA

Aluminum alloy 5052 (Al 5052) is one of the metals used as a bipolar plate in a Proton Exchange Membrane Fuel Cell (PEMFC) due to has its light mass and being easy to form, and, has high conductivity and resistivity properties. This material is prone to corrosion and current knowledge to protect its surface is currently lacking. The product of PEMFC produces electrical energy, hot steam (313 – 353 K), and water. These conditions have an impact on the degraded bipolar plate caused by the acidic nafion membrane. This increases the risk of corrosion on the cathode side of the bipolar plate. Coating with a green inhibitor using the electrophoretic deposition technique (EPD) is one way to deal with the corrosion that occurs. The analysis method used electrochemical with potentiodynamic polarization techniques, electrochemistry impedance spectroscopy (EIS), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). In this study, green inhibitor D-galactose was used with a concentration of 0.5 – 1.5 g and an, EPD time of 15 – 45 minutes in 0.5 M sulfuric acid (H2SO4) media pH 1-4. Potentiodynamic polarization analysis at the lowest corrosion current value (Icorr) at demonstrates (the inhibitor concentration of 1.5 g with an and EPD time of 45 minutes) resulted corrosion rate of Al5052 before EPD was 0.0075 mmPY while the corrosion rate of Al5052 after EPD was 0.0041 mmPY with (inhibitors efficiency 45.2%). The FTIR spectrum, broad peak appeared in the range of 3000-3600 cm-1, which refers to the formation of hydrogen bonding of hydroxyl group. Methyl group of D-galactose also appear on 2918 cm-1 and 2850 cm-1 which attributed to =CH2 asymmetric stretch and −CH3 symmetric stretch, respectively. Carbonyl group on 1500 – 1700 cm-1 represent C=O bond of amide, and aldehyde. Peak 1097 – 1035 cm-1 which attributed to C-O were connected to the secondary and primary alcohols. The resistance value for Al5052 before and after EPD are 1.2 kΩ/cm2 after and 2.2 kΩ/cm2, respectively. Here we find that the resistance increases with the increasing concentration and time of EPD. The results cross section Al5052 within average 29.8 μm, and morphology with SEM Al5052 before EPD showed pitting corrosion. On the other hand, the image of Al5052 inhibitor coating 1.5 gr with EPD of 45 minutes shows a smooth surface and visible black lumps, suggesting Al5052 is successfully reduced a corrosion rate by the D-galactose. Our simple and robust method inferred a protection route towards a viable and physically stable green inhibitors.

Synthesis, Electrochemical, Morphological, Computational and Corrosion Inhibition Studies of 3-(5-Naphthalen-2-yl-[1,3,4]oxadiazol-2-yl)-pyridine against Mild Steel in 1 M HCl

1,3,4-Oxadiazole derivative, namely, 3-(5-naphthalen-2-yl-[1,3,4]oxadiazol-2-yl)pyridine (NOP) as a corrosion inhibitor against mild steel in 1M HCl has been evaluated using the weight-loss technique (303-323 K), electrochemical analysis [potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS)], as well as surface morphology investigations (SEM). Additionally the computational studies such as density functional theory (DFT), the synthesized molecule (NOP) were utilized to better insight into molecular structure and electronic aspects relating to the anti-corrosion activities of the examined inhibitors and to envisage the interaction between designed inhibitors with the mild steel surface. The synthesized molecule (NOP) expressed high inhibition efficiency of 88.62% at an optimal concentration of 500 ppm at 298 K. A mixed-type inhibition mechanism is suggested by potentiodynamic polarization (PDP) analysis. The DFT calculations complement well with the experimental outcomes. This article provides in-depth insights to comprehend the mild steel inhibitor interactions mode and can be very helpful in accentuating the approach to mitigate the metal dissolution occurring in acidic corrosive media.

EVALUATION OF CORROSION PROTECTION CAPACITY OF DOPED PPY FILM FOR STAINLESS STEEL IN AN ACIDIC MEDIUM

Advanced corrosion protection methods include covering stainless steel surfaces with conductive polymer-based coatings. Polypyrrole and polypyrrole composites of tungstate of different concentrations were deposited on stainless steel-304 using cyclic voltammetry and their elemental analysis was verified by EDX analysis. EIS and potentiodynamic polarization analysis show that the corrosion protection efficiency (CPE) of polypyrrole composites is higher than polypyrrole coating. The reduction in corrosion rate due to the inhibitory action of tungstate through the physical barrier and anodic protection mechanism was validated by greater Rct and lower Icorr values of polypyrrole composites. In the composites, with increasing the concentration of tungstate in polypyrrole from 5% to 15%, CPE also increases, as polypyrrole composites are more able to shift the corrosion potential of stainless steels towards the passive zone and form a new nonporous passive oxide film on the surface. With a 15% concentration coating, the highest CPE of 93% and the lowest corrosion rate of 130 mmpy were obtained, indicating that the entire stainless steel active surface area is completely absorbed and that no active sites exit for adsorption at this concentration. The synthesized polypyrrole composites with a 15% concentration offer excellent corrosion protection prospects.

Structure Optimization of a Fe-Mn-Pd Alloy by Equal-Channel Angular Pressing for Biomedical Use.

In this work, a Fe-Mn-Pd alloy was produced by methods of equal channel angular pressing (ECAP) in order to obtain an alloy with a high rate of degradation for the development of biodegradable devices. Special efforts were made to the obtaining of an ultrafine-grained structure of alloys in a fully austenitic state at temperatures of 300 °C and 450 °C. Further investigation of its effect on the corrosion rate and mechanical properties was carried out. The formation of an austenitic structure with structural element sizes of 100-250 nm after deformation was confirmed by X-ray diffraction analysis. ECAP proved to be the reason for a significant increase in strength with maximum σUTS = 1669 MPa and σYS = 1577 MPa while maintaining satisfactory plasticity. The alloy degradation rate was investigated using the potentiodynamic polarization analysis. The corrosion rate of the alloy after ECAP (~1 mm/y) is higher than that of the coarse-grained state and significantly higher than that of annealed iron (~0.2 mm/y). ECAP in both modes did not impair the biocompatibility of the Fe-Mn-Pd alloy and the colonization of the sample surface by cells.