Potentiodynamic Polarization Studies Research Articles

Corrosion mitigation of mild steel by dimethylol propionic acid: an experimental and theoretical insights with in-vitro cytotoxicity testing on L929 cells

ABSTRACT The corrosion inhibition of mild steel (MS) in 1 M HCl acid utilising Dimethylol propionic acid (DMPA) as an inhibitor has been examined using electrochemical methods (PDP and EIS), both with and without DMPA. The inhibition efficiency at 298 K was determined by increasing the inhibitor concentration (DMPA), which exhibited a maximum effectiveness of 77.93% at 400 ppm for potentiodynamic polarisation (PDP) studies. Atomic force microscopy (AFM) and SEM revealed a protective coating form on the metal surface. The cytotoxicity of the sample was tested in L-929 cells using an MTT cell viability assay revealing that DMPA exhibited no toxicity to mouse fibroblast cells at concentrations up to 40 µg/mL after 24 h of incubation. Density Function theory (DFT) investigations revealed that inhibitors not only transfer electrons from reactive sites to the vacant orbital of the reactive metal but also receive valence electrons from the substrate metal, establishing a protective layer on the metal surface in an acidic solution.

Evaluation of galvanic corrosion in mild steel, 309S and 409M alloy combinations for marine environment applications

Abstract The objective of this study is to simulate galvanic corrosion in 409M, 309S (weld filler)-& MS joints couples during in light of field applications and to compare with the corrosion rates of the individual grades. Metals undergo corrosion when exposed to outdoor environments. But the rate of corrosion gets accelerated when the metals are connected to form a galvanic couple and are exposed to marine environments. One such galvanic system being used in coastal aggressive environments like marine applications can be combinations of Mild steel (MS)- 409M (Ferritic Stainless Steel) system welded using& 309S (Austenitic Stainless Steel) filler. The electrochemical tests which include measurement of voltage/current w.r.t time, cyclic potentiodynamic polarization studies and electrochemical impedance measurements using 5% NaCl solution were designed in order to assess how these alloys behave (i) individually and (ii) in galvanically-coupled states. Visual observations, determination of corrosion rates, microstructural inspections and Scanning Electro Microscopy (SEM) analysis were carried out as a part of corrosion evaluation method. The results indicated that the galvanic coupling of dissimilar metals significantly accelerates the corrosion rate of the less noble metal, particularly in the MS-309S couple where the difference in their corrosion potentials between the two alloys is as high as 450 mV. The corrosion rate of MS coupled with 309S increased to 0.277 mm/yr, which is approximately 6.9 times more compared to the MS-MS couple. From the above study, it was found that the MS samples experienced higher corrosion rates when coupled with 309S, followed by MS in MS-409M system. The comparison was done with respect to MS-MS system. The test data shall be used to compare the relative corrosion resistances of (i) MS - MS (ii) MS - 409M (iii) 409M – 409M (iv) 309S - 409M (v) 309S - MS and (vi) 309S – 309S. This is required to understand the relative corrosion resistances of alloys during field application and to arrive at a suitable solution for maximizing its service life.

Exploring the bio-inspired corrosion inhibition properties of eco-friendly Limonia acidissima leaves extract for mild steel in acidic media: Computational, electrochemical and spectroscopic insights

This study investigates the corrosion inhibition properties of Limonia acidissima leaves extract (LALE) on mild steel in a 1.0 M HCl medium. Utilizing mass loss measurements, potentiodynamic polarization, AC impedance spectroscopy, and surface characterization methods like SEM, AFM, UV–Vis, and fluorescence spectroscopy, the study reveals significant findings. The maximum inhibition efficiency of LALE was attained to be 92.26 % at a 1.0 % concentration. Potentiodynamic polarization studies show a marked decrease in corrosion current density (Icorr) from 3.102 × 10–3 A/cm² for the blank solution to 3.165 × 10–4 A/cm² with 1.0% LALE, indicating mixed-type inhibition. AC impedance measurements show an increase in charge transfer resistance (Rct) from 2.1410 Ω in the blank solution to 8.6580 Ω with 1.0% LALE, and a decrease in double-layer capacitance (Cdl) from 7.757 × 10–7 μF/cm² to 1.926 × 10–7 μF/cm², suggesting the formation of a protective film. SEM and AFM analyses confirm that LALE-treated steel surfaces are smoother with fewer pits and cavities compared to untreated steel. Furthermore, DFT analysis complemented well with the empirical findings. This research highlights the potential of plant extracts in industrial applications for corrosion protection, contributing to the growing body of knowledge on sustainable corrosion inhibitors and offering practical insights for future research and application in various corrosive environments.

Functionalized polyaniline nanofibrils on lamellar structured zirconium for effective bone mineralization

The surface physiology of certain implant material has the ability to promote implant–cell signalling process through which a stable environment is formed. The formation of this favourable environment hastens the process of biomineralization and regeneration. In this context, Zirconium (Zr) when treated with alkali undergoes a surface modification which results in the development of a lamellar structured Zirconium (ATZ). Further, encapsulation of polyaniline (PAni) on ATZ was achieved through the electropolymerization technique which results in an effective and homogeneous electrodeposition of PAni nanofibrils on ATZ surface. A high resolution scanning electron microscope analysis (HR-SEM), phase analysis and functional group analysis were carried out confirming the semi-crystalline PAni nanofibrils braided on the ATZ surface. Potentiodynamic polarization studies of the coated sample exhibited higher Ecorr (−0.060 V) and lower icorr (0.007 µA/cm2) values signifying its better corrosion resistance behaviour in higher potentials coupled with lower electrochemical activity in the SBF medium. The porosity of PAni/ATZ nanofibril was 0.007 % and it provides an effective platform for implant-tissue attachment. The In-vitro biomineralization studies proved the bioactivity of PAni/ATZ which forms well-matured HAp spherules over the surface. Further, hemocompatibility studies of PAni/ATZ expressed a hemolytic rate of ∼0.39 % which denotes it’s biocompatible and non-hemolytic behaviour with the blood cells. Further, the coated sample on gram-positive and gram-negative bacteria causes demise of bacterial cell wall and exhibits higher inhibition percentage. In addition, a standard MTT assay of PAni/ATZ provides an effective support in maintaining cell viability and aids in proliferation of MG-63 cells. Thus, the results demonstrate that the nanoscale surface architecture of PAni/ATZ could serve as a potential and conducive environment for bone-implant interaction on the implant material for better osseointegration.

Thermal fluctuations on the corrosion behaviour of 17-4PH stainless steel alloys fabricated via material extrusion additive manufacturing technique

Herein, the influence of fluctuating thermal conditions on the corrosion behaviour of 17-4PH stainless steel alloys manufactured via fused filament fabrication is reported. The printed samples were sintered and then exposed to different temperature-fluctuating conditions to simulate the application environment of such alloys. The first set of samples (A) was studied as-sintered, the second set of samples (B) was aged at 480°C for 3 h followed by quenching in water, the third set (C) was exposed to conditions of B followed by aging at 360°C for 3 h and quenching in water and the final set of samples (D) was exposed to conditions of C followed by aging at 200°C for 3 h, quenching in water, aging at 400°C for 3 h, and finally quenching in water. The surface roughness evolved with the temperature conditions. The optical microscopy revealed that sample B had a fine and homogenous distribution of precipitates. Sample B had the highest microhardness values followed by C, D, and A in that order. XRD analysis revealed the presence of retained FCC austenitic phases within the microstructure whose peaks became stronger with the increased thermal fluctuations. The potentiodynamic polarisation studies revealed a distinct linear Tafel region on the cathodic region and a dual-slope inflection point on the anodic region of the polarisation curves. Sample D exhibited the highest corrosion rate whereas sample B revealed the lowest. As such, exposing fused filament fabricated 17-4 PH SS to fluctuating temperature conditions leads to degradation of mechanical strength and corrosion resistance.

Aromaticity of Heterocyclic Compounds and Their Corrosion Inhibition Property: Experimental and Theoretical Analysis.

Heterocycle derived moieties, namely, N-(4-methoxyphenyl)-1-(1H-pyrrol-2-yl)methanimine (MPM), 1-(furan-2-yl)-N-(4-methoxyphenyl)methanimine (FMM), and N-(4-methoxyphenyl)-1-(thiophen-2-yl)methanimine (MTM), were synthesized followed by analysis of their structural aspects using FTIR and 1H NMR spectroscopic techniques. The corrosion retarding abilities of the same were distinguished by gravimetric and certain electrochemical measures for mild steel in 0.5 M H2SO4, and MTM was obtained with maximum inhibition efficiency of 97.93% at 250 mg L-1 concentration; the thermodynamic and activation parameters were recorded in this regard. The results were further seen to be supported by various surface studies: SEM-EDS, XPS, AFM, contact angle, and UV-visible spectroscopy. Potentiodynamic polarization studies unveiled the mixed nature of heterocyclic inhibitors with overriding anodic effect. Furthermore, the adsorption of inhibitors over mild steel coupons demarcates the prevalence of physical and chemical interactions in the environment. In addition, the computational studies, global and local reactivity, molecular dynamics, and density functional theory, were employed and the experimental results obtained were found in correlation with the theoretical results.

Synthesis and Characterization of Ni(II) Schiff Base Complex as a Precursor for NiO Nanoparticles and an Investigation of Their Corrosion Inhibition

This study first aimed to synthesize and characterize a [Ni(C14H13NO2)(OAC)2(H2O)2] via the preparation of a ligand, coordination with Ni(II) ions, and full characterization, such as "FTIR, 1H and 13C-NMR, UV-Visible spectroscopy; and ESI-mass spectrometry" The Nickel complex was then used as a precursor to prepared NiO Nps by calcination at 450°C. The phase purity, crystalline structure, and morphological characterizes of the NiO nanoparticles were investigated via X-ray diffraction (XRD), FESEM, and FTIR spectroscopy, revealing them to be cubic system with an average crystalline is 26 nm. The preparation technique is facile, cost-effective, and rapid and suitable for generating NiO nanoparticles for use in industrial processes. Further, the corrosion inhibition effectiveness of all synthesized compounds on mild steel in 1 M HCl was evaluated. Their inhibition efficiencies were determined via potentiodynamic polarization studies, revealing the highest inhibition efficiency for the NiO nanoparticles compared to the Nickel complex and free a ligand.

Corrosion Inhibition Potential of Aqueous Extract of Bauhinia acuminata Linn Leaves on Carbon Steel in Hydrochloric Acid Medium

The corrosion of carbon steel in 1 N HCl was analyzed using an aqueous Bauhinia acuminata Linn (BaL) leaf extract. Weight loss method was used to determine the inhibitor efficaciousness and corrosion rate. When dissolved in water, a linneus plant leaf extract exhibit an inhibitory effect which is proportionate to the amount of inhibitors present. It is possible to speed up the corrosion process by increasing the inhibitors’ concentration. Studies have shown that the BaL leaves extract has a 97.30% inhibitory efficiency. By increasing the concentration of inhibitor solutions, a surface layer forms on carbon steel, which inhibits the activity of the active site. The potentiodynamic polarization (PDP) and AC impedance studies (EIS) were employed to examine the mechanical properties of corrosion inhibition. The surface homogeneity and irregularity of carbon steel were examined using AFM and SEM under polished, corroded and inhibitor-treated surfaces. The surface irregularity of the carbon steel were analyzed using atomic force microscopy.

An electrochemical and theoretical approach towards the efficient microwave synthesis of imidazolium-based ionic liquids for unprecedented mild steel corrosion inhibition in 0.5 M H2SO4 solution

The inhibition potential of newly synthesized imidazolium-based ionic liquids (IL-1 and IL-2) on mild steel corrosion in a 0.5 M H2SO4 solution has been comprehensively investigated using gravimetric analysis, potentiodynamic polarization, and electrochemical impedance spectroscopy across various temperatures. Gravimetric analysis indicated that the adsorption of these inhibitors adhered to the Langmuir adsorption isotherm. Significantly, IL-2, featuring a longer alkyl chain, demonstrated superior inhibition efficiency (92.51 % at 303 K) compared to IL-1 (88.71 % at 303 K). Potentiodynamic polarization studies revealed a mixed-type inhibitory behavior, impacting both anodic and cathodic reactions. Surface morphological analyses via SEM and EDX confirmed the formation of a protective film on the mild steel surfaces, substantiating the corrosion inhibition capabilities of IL-1 and IL-2. The novelty of this research lies in the application of density functional theory (DFT) using the B3LYP method, which elucidated that the alkyl chain length at the N-3 position in imidazolium cation-based ionic liquids significantly enhances their inhibition potential. This mechanistic insight suggests that these ionic liquids effectively obstruct both anodic and cathodic sites, providing robust corrosion protection in a 0.5 M H2SO4 solution.

Sodium salt of dodecyl benzene sulphonic acid as an effective corrosion inhibition for different heat-treated steel in sulphuric acid medium

Abstract The purpose of this work is to use electrochemical and gravimetric techniques to investigate the inhibition of DBSS on the corrosion of heat-treated dual-phase AISI 1040 steel in a 0.5 M sulphuric acid solution at 35 °C. The corrosion studies are performed by potentiodynamic polarization study (PDP), electrochemical impedance study (EIS), and gravimetric method. To confirm the inhibition surface characterization like x-ray diffraction technique (XRD) analysis, scanning electron microscopy (SEM), and EDS analysis are performed. Depending on the phase change of metals due to heat treatment, the corrosion inhibition of the heat-treated metal increased when it was exposed to 0.5 M H2SO4 at 35 °C in the presence of dodecyl benzene sulphonic acid sodium salt (DBSS) inhibitor. The highest inhibition efficiency of 63%, 82%, 87%, 43%, and 63% was obtained for AISI 1040 steel at heat treatment conditions of Normalized, Quenched at 700 °C, Quenched at 750 °C, Quenched at 790 °C and Quenched at 900 °C respectively. In the gravimetric and electrochemical study, the IE increases with the increase with the concentration of DBSS unto 75% from gravimetric analysis and 87% from PDP analysis for Quenched at 750 °C and 790 °C respectively. The metal protection is achieved by heat treatment process as well as by using DBSS as inhibitor. Corrosion inhibition on the metal’s surface was confirmed by SEM and XRD. In addition, the adsorption of DBSS on the anodic and cathodic sites of the metal surface was well explained.

Enhanced anti-corrosion characteristics of epoxy-functionalized graphene oxide nanocomposite coatings on mild steel substrates

This experimental investigation focused on coating of functionalized graphene oxide (FGO) on the mild steel to minimize corrosion, using a new method. Prior to the coating, the fundamental chemical and morphological structures of FGO were studied with aid of some characterization techniques: X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Various epoxy/FGO coating formulations with 10, 20, 30, 40 and 50 ppm of FGO were prepared and coated on the mild steel substrate, adopting dip coating method. Immersion test was carried out to observe the corrosion inhibition efficiency of the graphene. The adsorption isothermal behavior was also studied using various models and compared with the data obtained from the experimental results. From the results obtained, the formation of irregular rough patches and separation of platelets like zebra lines indicated the formation of graphene nanoparticles, as observed through morphological analysis. The occurrence of sharp peak at 24.3° in the XRD pattern depicted the existence of graphene in nanoscale. Electrochemical impedance (EI) and potentiodynamic polarization (PP) studies reported the maximum corrosion inhibition efficiency of 87% at 50 ppm concentration of epoxy/FGO. It was evident that an increasing concentration of graphene exhibited significant corrosion resistance in both studies. The bonding energy of randomly oriented graphene platelets reduced the removal of metal, delaying the crack propagation in tortuous path on the coated surface. These results established the significance and applicability of this study in various relevant industries.

Exploration of UV-induced geometrical isomer-enriched Helichrysum kraussii extract as a corrosion inhibitor for Al(111) surface in 1.0 M hydrochloric acid: An experimental and theoretical study

This study evaluated UV-radiated Helichrysum kraussii (H. kraussii) extract for its corrosion inhibition on aluminium in 1.0 M HCl. To achieve this, techniques such as Liquid chromatography-mass spectrometry (LC-MS), Fourier transform infrared spectroscopy (FTIR), Gravimetric analysis, electrochemical analysis looking at electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP), contact angle and computational studies were used. The results obtained from these techniques made it possible to conclude the performance of UV-radiated H. kraussii as a corrosion inhibitor for aluminium metal. LC-MS and FTIR proved that the exposure of extract to UV radiation caused a change in the composition of extract metabolites, demonstrated by the increase in the number of peaks in the chromatogram and the shift in the FTIR spectrum. Weight loss technique showed that the extract inhibited the corrosion of aluminium with the maximum percentage inhibition of 84.6948 % at the concentration of 1500 ppm at 30 °C. The adsorption of the inhibitor molecules on the metal surface was found to obey the Langmuir adsorption isotherm, and the activation energy values proved that the adsorption mechanism was through physisorption. Nyquist plots semi-circles were found to increase with an increase in the extract concentration, showing an increase in the inhibition efficiency. Tafel's plot showed that both anodic and cathodic corrosion were inhibited. The DFT/PBE/GGA/DNP computational investigation obtained binding energies of the inhibitors on the aluminium surface that suggest that the Al···FA interaction happens through physical adsorption.

Grape Seed Extract as an Environment-Friendly Green Inhibitor for Corrosion of Mild Steel in 1 M Sulfamic Acid

A corrosion inhibition study of mild steel in 1 M sulfamic acid was conducted using grape seed extract (GSE) as a possible green inhibitor. Electrochemical techniques were adopted to measure the corrosion rate in both the absence and presence of the GSE. Conditions were standardized to obtain optimum inhibition efficiency by varying the concentration of inhibitor and temperature. The kinetic parameters were calculated using the Arrhenius equation. Surface analysis was conducted by scanning electron microscope (SEM) and atomic force microscope (AFM) techniques. A suitable mechanism was proposed for the corrosion inhibition process. Grape seed extract showed a maximum efficiency of 65%, with a concentration of 0.24 g/L at 303 K from potentiodynamic polarization (PDP) studies. With the increase in temperature, the efficiency decreased, resulting in the GSE inhibitor’s physical adsorption. Surface morphology studies supported the adsorption of GSE on mild steel. GSE acted as an efficient green inhibitor with environmental benefits.

Experimental investigation and theoretical modeling of copper corrosion inhibition by Urginea maritima essential oil

Corrosion inhibition is essential for preserving metallic materials in various industrial applications. This study aims to assess the inhibition performance of Urginea maritima essential oil (HEUM) in mitigating copper corrosion within a 0.5 M sulfuric acid environment. The experimental investigation examined the inhibition properties of the essential oil using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization studies (PDP) and surface analysis by scanning electron microscopy (SEM). In addition, theoretical studies have been carried out using density functional theory (DFT) to further elucidate corrosion inhibition mechanisms. The findings from both experimental and theoretical analyses suggest a notable reduction in corrosion rates with the essential oil, highlighting its promising efficacy as an inhibitor, and the inhibitory effect of HEUM essential oil can be attributed to a synergistic effect between its various components. Furthermore, thermal stability studies demonstrate sustained inhibitory action over a range of temperatures. These results demonstrate the high potential of HEUM as a natural and eco-friendly corrosion inhibitor, warranting further exploration of practical applications in corrosion control strategies.

Comparison of the corrosion behaviour of 10Cr and 17Cr Al added ODS steel in simulated reprocessing nitric acid medium

It is imperative to comprehend the corrosion behavior of different Cr containing Al-added ODS steel reactor clad materials in nuclear reprocessing simulating conditions, as high dissolution of clad material is not desirable. In this present work, the effect of varying HNO3 concentrations (3, 6, 11.5 M HNO3) and with oxidizing (Cr6+, Ce3+) and non-oxidizing (Fe3+) ions in 6 M HNO3 on 10Cr (10Cr-5Al-0.5Ti-0.5Y2O3-Fe) and 17Cr (16.78Cr-4.46Al-0.5Ti-0.45Y2O3-Fe) Al-ODS steels are investigated. The potentiodynamic anodic polarization studies revealed an ennoblement of corrosion potential by elevated cathodic current resulting from increased oxidizing conditions in HNO3 by concentration and oxidizing ions. Through various electrochemical techniques like open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), the 17Cr Al-ODS steel exhibited improved corrosion resistance with lower Ecorr, increased passivation range (Epass range), lower corrosion current density (icorr) and increased charge transfer resistance (Rct). The SEM studies revealed variation in corrosion morphology as shallow corrosion cavities and deeper corrosion pits in 17Cr Al-ODS and 10Cr Al-ODS steel, respectively, at high oxidizing environment. The enhanced corrosion resistance of 17Cr Al-ODS is associated to the improved passivation with the high Cr level in the steel compared to 10Cr-ODS steel, which is corroborated by XPS analysis. New knowledge on nitric acid corrosion mechanism on the Cr in Al-ODS steels and the influences of oxidizing ions in reprocessing environments are described.

Comprehensive Investigation of the Adsorption, Corrosion Inhibitory Properties, and Quantum Calculations for 2-(2,4,5-Trimethoxybenzylidene) Hydrazine Carbothioamide in Mitigating Corrosion of XC38 Carbon Steel under HCl Environment.

This study investigates the inhibitory effects of 2-(2,4,5-trimethoxy benzylidene) hydrazine carbothioamide (TMBHCA) on the corrosion of carbon steel in a 1 M HCl solution across various concentrations. The assessment employs a comprehensive approach, combining gravimetric analysis, potentiodynamic polarization tests, and electrochemical impedance spectroscopy (EIS). Additionally, scanning electron microscopy (SEM) and quantum chemical calculations are employed to provide a thorough understanding of the corrosion inhibition mechanism. The influence of exposure time on mild steel corrosion is systematically examined. Results reveal a remarkable reduction in the corrosion rate of steel, with TMBHCA demonstrating its highest inhibition efficiency of 97.8% at 200 ppm. Potentiodynamic polarization studies characterize TMBHCA as a mixed-type inhibitor, while Nyquist plots illustrate increased charge transfer resistance and decreased double-layer capacitance with escalating TMBHCA concentrations. Consistency between weight loss measurements and electrochemical findings further validates the efficacy of TMBHCA as a corrosion inhibitor. SEM images substantiate and visually support the obtained results. An immersion test conducted at 25 °C over 28 days showcases a notable enhancement in TMBHCA efficiency (IE%) from 45.16% to 92.43% at 200 ppm as the immersion period progresses from 1 day to 28 days. This improvement is attributed to the augmented adsorption of inhibitor molecules on the steel surface over time. These comprehensive findings significantly contribute to our understanding of TMBHCA's corrosion inhibition behavior, emphasizing its potential as a highly efficient corrosion inhibitor for diverse industrial applications.

BF2 complexes of pyridyl‐isoindoline‐1‐ones as an efficient corrosion inhibitor for mild steel in 1 M HCl and the application for surgical instruments anticorrosion

AbstractIn this study, BF2 complexes of pyridyl‐isoindoline‐1‐ones (BPIO) has been firstly designed and investigated as an excellent corrosion inhibitor for the mild steel in 1 M HCl. The corrosion protection properties of BPIO were studied by using a series of experiments. The results indicated BPIO has excellent inhibition performance, and inhibition efficiency of BPIO reached up to 96.6%. The effects of immersion temperature and time were investigated by weight loss experiments to evaluate the stability of adsorbed BPIO film in protecting steel surface. Based on potentiodynamic polarization studies, BPIO acted as one mixed‐type corrosion inhibitor with predominant anodic effectiveness, and its adsorption on the mild steel follows the Langmuir adsorption isotherm. The values of ΔGads suggested the adsorption of BPIO on the mild steel surface was through a combination of chemisorption and physisorption. The adsorption of BPIO molecules on the steel surface was further identified by the techniques of scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS). The quantum chemical calculations based on density functional theory (DFT) and molecular dynamics (MD) simulations were used to optimize the BPIO molecular structure and investigate the inhibitive properties on the theoretical level, which agreed well with the experimental results. Besides, BPIO has been used for the development of water soluble metal antirusting agent.

Assessment of the microstructural features and electrochemical corrosion behaviour of nanostructured Gd2Zr2O7 EB-PVD TBCs under three salt conditions

Improving corrosion resistance is a challenging task, as it determines the life time of thermal barrier coatings (TBCs). In this regard, this study was aimed to characterize the electrochemical corrosion behaviour of nanostructured Gadolinium Zirconate in three different corrosive salt conditions such as Na2SO4 + 55 wt% V2O5 (SM1), Na2SO4 + 10 wt% NaCl (SM2), and Na2SO4 + 7.5 wt% NaCl +7.5 wt% V2O5 (SM3). The uniformity of the coated surface was verified by mapping the vibrational bands associated with Gd and Zr using FT-IR and Raman spectroscopy. The coated surface possessed a uniform columnar structure with leafy appearance. Potentiodynamic polarisation studies and electrochemical impedance spectroscopic data demonstrated that the nanostructured GZ exhibited superior corrosion resistance properties under SM1 salt condition as compared to SM2 and SM3 conditions. SEM and EDS analysis were used to evaluate the nanostructured GZ coatings that were subjected to electrochemical corrosion. In the case of SM2 and SM3 conditions, the surfaces were degraded with microcracks. The formation of corrosion products and the exposure of succeeding layers as a result of corrosion were also characterized using FT-IR, Raman spectroscopy, XRD technique and 3D optical microscope.

ZnO-functionalized arabinogalactan and xylan nanocomposite epoxy coating for the corrosion protection of AISI 5140 steel

The anticorrosion performance of epoxy coatings can be enhanced by using biopolymer nanocomposites. The permeability of the corrosive ions through defects and pores can be prevented by the functionalization of biopolymers and their introduction into the epoxy matrix. Herein, ZnO-functionalized arabinogalactan and xylan (AG-ZnO and XL-ZnO) nanocomposites were fabricated using ultrasonication and characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). The surface morphology of the prepared biopolymer nanocomposite was analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (HR-TEM). The corrosion performance of the epoxy coating containing AG-ZnO and XL-ZnO on AISI 5140 steel was evaluated via electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization studies (PDP) in 3.5 wt% NaCl. The results indicated superior corrosion protection, with inhibition efficiencies of 89.71 % and 93.27 % for the AG-ZnO and XL-ZnO incorporated epoxy coatings, respectively. Furthermore, 0.3 wt% of the prepared biopolymer nanocomposite in the epoxy coatings provided superior protection due to the increased dispersion and even distribution of zinc oxide. After the introduction of the XL-ZnO and AG-ZnO biopolymer nanocomposites, there was a threefold and twofold increase in the charge transfer resistance, respectively, compared to that of the pure epoxy coating. Compared to those of the pure epoxy (icorr = 1.23 ×10-6 A cm−2), the icorr values of the XL-ZnO-EP (icorr = 0.16 ×10-6 A cm−2) and AG-ZnO-EP (icorr = 0.65 ×10-6 A cm−2) coatings significantly decrease. The prepared coatings were subjected to water contact angle measurements and the 3D topographical morphology was determined using atomic force microscopy (AFM). A reduced roughness was observed for the prepared coatings.

Corrosion inhibition of stainless steel through the formation of hydrophobic nanoporous oxide layer

This study investigates anti-corrosion properties of anodized and hydrophobically modified anodized SUS 304 stainless steel (SS 304). Utilizing electrochemical anodization and subsequent annealing, a well-ordered hexagonally closed-packed nanoporous oxide layer on the SS 304 surface, designated as AAS, was successfully developed. Then, a self-assembled monolayer of silane molecules, namely, octadecyltrimethoxysilane (ODTS) and 1 H,1 H,2 H,2 H-perfluorooctyltriethoxysilane (PFTS), was formed on the nanoporous oxide layer of annealed-anodized SS 304. The FTIR study confirmed the formation of the self-assembly of silane molecules on nanoporous oxide surface. The self-assembled monolayers exhibited hydrophobic surface where hydrophobicity increases with increase of silane molecule concentration and gives a water contact angles measure of 127.60° and ∼ 128.83° for 0.50 wt% ODTS and 0.50 wt% PFTS, respectively. The potentiodynamic polarization study revealed a corrosion rate of 1.485 × 10−3 mm year−1 for AAS, 0.614 × 10−3 mm year−1 for 0.50 wt% ODTS-AAS, and 0.348 × 10−3 mm year−1 for 0.50 wt% PFTS-AAS. This represents a significant reduction in corrosion rate compared to bare stainless steel (4.385 × 10−3 mm year−1) when exposed to a simulated sea water environment. The AAS, 0.50 wt% ODTS-AAS and 0.50 wt% PFTS-AAS exhibited corrosion inhibition efficiency of 66.13 %, 85.97 % and 92.06 %, respectively. Electrochemical impedance analysis revealed that PFTS exhibits roughly double the effective charge transfer resistance of ODTS and 7.4 times higher than that of annealed anodized stainless steel, confirming superior corrosion inhibition capability. Overall, this research illuminates the mechanism behind self-assembled monolayer formation, resulting in the development of hydrophobic surfaces and the inhibition of corrosion on nanoporous oxide layers on stainless steel surfaces.