Surface Corrosion Research Articles

Relation between Surface Appearance and Corrosion Depth Distribution of Carbon Steel under Atmospheric Corrosion Environment

Relation between Surface Appearance and Corrosion Depth Distribution of Carbon Steel under Atmospheric Corrosion Environment

Design and Corrosion Resistance Performance of Nano-Multilayer Coatings for the Protection of Breathing Gas Cylinders Used in Diving

Seamless gas cylinders for diving exhibit excellent low-temperature impact performance, lightweight characteristics, and good corrosion resistance, making them widely applicable in underwater activities. However, during use, the peeling of paint or corrosion on the surface of these cylinders poses a significant threat to their safety. In this study, environmentally friendly arc ion plating technology was used to deposit TiBN, CrAlN, and nano-multilayer coatings of CrAlN/TiBN. The surface morphology, tribological properties, and corrosion resistance of these coatings were investigated. The results indicated that both CrAlN and CrAlN/TiBN coatings possess fewer droplets, pinholes, and pits, and the cross-section of the CrAlN/TiBN coating exhibits a denser structure. The preferred orientation for TiBN was identified as TiB2 (101), while that for CrAlN was Cr(Al)N (200), with the preferred orientation for CrAlN/TiBN being TiB2 (101). The friction measurements revealed that the lowest coefficient was observed in the CrAlN/TiBN coating (0.489), followed by CrAlN (0.491) and then TiBN (0.642). Electrochemical tests conducted in artificial seawater demonstrated that the self-corrosion potential was highest for the CrAlN/TiBN coating, followed by CrAlN and lastly TiBN. The developed TiBN-based nano-multilayer coatings hold substantial application value in protecting seamless gas cylinders used in diving.

Enhanced corrosion protection of copper in saline environments using bio-nanocomposite coatings based on chitosan and chitosan Schiff base

An in-depth study focuses on developing new environmentally friendly bio-nanocomposites, by incorporating SrTiO3 (STO) ceramic nanoparticles into matrices of chitosan and its derivatives, aiming to use them as protective coatings against corrosion. The various stages of this study include the cross-linking of chitosan, the synthesis of Schiff base chitosan, the cross-linking of Schiff base chitosan, and the preparation of nanocomposite coatings. The coatings' structure and composition were analyzed using different methods, including Fourier Transform Infrared Spectroscopy - Attenuated Total Reflectance (FTIR-ATR), X-ray Diffraction (XRD), Transmission Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (TEM-EDX), and Scanning Electron Microscopy (SEM). In addition, Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PDP) measurements were carried out to assess the inhibitory efficacy of chitosan crosslinked with epichlorohydrin (Cs-Ep), epichlorohydrin-crosslinked chitosan-salicylaldehyde Schiff base (CS-S-Ep) and CS-Ep-STO and CS-S-Ep-STO nanocomposite coatings, as well as the long-term protection durability of CS-S-Ep-STO. These techniques revealed a significant reduction in corrosion current density after chemical modification of chitosan and incorporation of SrTiO3 (STO) nanoparticles into CS-Ep and CS-S-Ep matrices, confirming a notable improvement in the inhibitory efficiency of these coatings against copper corrosion in a saline environment. Computational modeling methods like Density Functional Theory (DFT), Molecular Dynamics (MD), and Monte Carlo (MC) simulations reinforced these results by demonstrating efficient adsorption of CS-S-Ep-STO nanocomposites on metal surfaces through the interaction with heteroatoms present in the functional groups (-C=N-, -C-O-, -OH) and STO nanoparticles. The present study's findings provide key information for developing innovative protective coatings, highlighting the potential of chitosan-based nanocomposites and derivatives, particularly with SrTiO3 incorporation, in mitigating metal surface corrosion in aggressive environments.

Effects of dust and rainfall on the relative reflectivity of linear Fresnel reflectors

Dust and rainfall have been key issues affecting outdoor solar concentrating systems. This study aimed to accurately evaluate the specific effects of dust and rainfall on linear Fresnel reflectors in semi-arid regions. Targeted outdoor experiments on dust and rainwater were conducted in Hohhot, Inner Mongolia, from September to December 2023. A predictive model is developed to assess the effect of rainfall on reflectivity under conditions of dust accumulation, based on the physical properties of outdoor-exposed dust. The study reveals that after 60 days of exposure, the reflectivity decreased at a rate of 0.25 % per day due to mirror dust, particularly within the 380–780 nm wavelength range, reaching 21.62 %. The rainfall leads to four distinct conditions, namely pitting, surface corrosion, gully corrosion, and overall corrosion on the dusty mirror. During the gully corrosion and corrosion stages, the reflectivity significantly improved. Rainfall below 0.4 mm barely cleaned mirror dust, whereas rainfall exceeding 26.70 mm provided substantial cleaning but reached a saturation point with additional rainfall. These findings contribute to the development of cost-effective cleaning strategies for similar climatic conditions.

The Effect of Metallographic Preparation on the Surface Characteristics and Corrosion Behaviour of Ti-6Al-4V Alloy in Simulated Physiological Solutions

Abstract This study aimed to determine the effect of surface metallographic preparation (grinding, diamond polishing, and chemo-mechanical polishing using silica and hydrogen peroxide) on the surface roughness, morphology, chemical composition, and electrochemical behaviour of Ti-6Al-4V alloy. Roughness decreases from ca. 0.2 m to 0.02 m from grinding to polishing. A typical + microstructure can be observed only after chemo-mechanical polishing. The average composition of ca. 6 wt.% Al, 4 wt.% V, and rest Ti was determined regardless of the surface preparation. X-ray phtotoelectron spectroscopy revealed that the thickness of the oxide layer formed on chemo-mechanical polished samples is half that of ground samples. The metallographic preparation largely affects the corrosion behaviour of Ti-6Al-4V, which was investigated using electrochemical impedance spectroscopy and potentiodynamic polarisation in 0.9 wt.% NaCl and artificial saliva at 37C. At the open circuit potential, the chemo-mechanically polished Ti-6Al-4 samples showed superior corrosion resistance over ground samples. At potentials over 2.5 V vs. Ag/AgCl, increased current densities were noted for chemo-mechanically polished samples, presumably related to the oxidation to a thicker oxide.

Surface microstructure and corrosion resistance characterization of Mg-based amorphous alloys

Surface microstructure and corrosion resistance characterization of Mg-based amorphous alloys

Cavitation erosion behaviour of MAB-CU4 alloy: influences of cavitation number, attack angle, time, and stand-off distance

Abstract The present study comprehensively examines the cavitation erosion behaviour of a manganese aluminium bronze alloy (MAB-CU4 alloy) as a function of several parameters (i.e., cavitation angle, cavitation number, time, and stand-off distance), particularly focusing on the influences of cavitation angle on the surface morphology and topography of the alloy. According to the design of experiment (Taguchi experimental design) analysis, mass loss increased with cavitation number and attack angle, while increasing the stand-off distance resulted in a decrease in mass loss and an increase in the surface area affected by cavitation erosion. Cavitation erosion behaviour was most affected by the cavitation attack angle, with the cavitation attack angle contributing 69.1% to total erosion, according to variance analysis. At 90° cavitation attack angle, MAB-CU4’s erosion rate was 64% greater than that at 30°. Scanning electron microscopy and optical profilometry revealed that cavitation erosion damage at 90° occurred mostly in the grain interiors as cavitation pits due to severe plastic deformation and surface corrosion, whereas pit formation was restricted around the hard secondary phases at the grain boundaries. At 30°, deep cavitation pits were limited, the erosion crater expanded, and the number of pits was reduced. Overall, finer microstructures with more grain boundaries and secondary phases may improve cavitation erosion resistance at 90°. The present study is the first to comprehensively capture erosion damage at the microstructural scale and analyse the impact of microstructural features on the erosion damage during the cavitation erosion of MAB-CU4 alloy.

Potential of water-soluble chitosan Schiff bases extracted from Metapenaeus dobsoni shells as effective corrosion inhibitors

Corrosion causes significant economic losses and structural failures in industries, highlighting the need for eco-friendly inhibitors. Chitosan (CS), a biodegradable and non-toxic biopolymer, shows potential, though its limited water solubility restricts its applications. To overcome this challenge, this study presents the synthesis of two water-soluble chitosan Schiff bases (CSBs) derived from the shells of Metapenaeus dobsoni (M. dobsoni). The extracted CS exhibits a remarkable degree of deacetylation exceeding 95 %, which was subsequently modified through reactions with o-vanillin (2-hydroxy-3-methoxybenzaldehyde) (CSB I) and 2,3-dihydroxybenzaldehyde (CSB II). Structural characterization using spectroscopic techniques confirmed the successful formation of CSBs. Electrochemical measurements were employed to assess the corrosion resistance of mild steel in 0.5 M HCl with varying concentrations of CSB I and CSB II. The results revealed superior corrosion inhibition by CSB II (% IE = 94.48 %) compared to CSB I (% IE = 88.80 %). The methoxy group in CSB II contributed to its higher electron density and enhanced adsorption, leading to better surface coverage and corrosion resistance. Both inhibitors followed the Langmuir isotherm, suggesting a mix of physisorption and chemisorption. These CSBs are promising for corrosion control in industries like pipelines, storage tanks, construction materials, and acid pickling.

Literature Review−Effect of Additives and Post-Treatments on Corrosion Resistance and Mechanical Properties of Plasma Electrolytic Oxidation Products in Magnesium and Titanium

<p class="Abstract">Plasma Electrolytic Oxidation (PEO) is a method of converting metal surfaces into an oxide layer with the help of plasma to improve the surface mechanical properties and corrosion resistance of metals. A PEO layer of about 10-50 μm is obtained quickly from 1 second-10 minutes at a voltage range of 150-500 V with AC or DC mode. Characteristics of the outer layer of PEO have pores and cracks, while the inner layer is relatively denser. Cracks and pores reduce the corrosion resistance and mechanical properties of the coating. In this study, a literature search was carried out on the effect of adding additives and post-treatment on the characteristics of PEO coatings grown on magnesium (Mg) and titanium (Ti) metals for biomedical applications. Mg and Ti metals have opposite chemical properties; Mg is a reactive metal, while Ti is an inert metal. Comparing the behavior of the PEO process and the coating produced by the two different metals is absorbing and necessary to understand the fundamentals of the PEO process. The results of a literature search show that the addition of additives increases the growth rate of the coating so that the coating is thicker and more wear resistant. The hardness of the coating also increases due to the additive particles trapped in the oxide layer filling the micro pores so that the surface becomes denser and more homogeneous. Therefore, corrosion resistance also increases, as indicated by a decrease in corrosion current as measured by the polarization test and an increase in the impedance modulus as measured by the electrochemical impedance test (EIS). The post-alkali treatment allows for increased surface bioactivity, as indicated by the rise in the Ca/P ratio after immersion in a physiological solution.</p>

Designing for the chemical conversion coating on AZ91 magnesium alloy by equalising interface potential difference

The formation of intermetallic compounds leads to heterogeneous chemical compositions and galvanic corrosion in alloy materials, which are widely recognised as primary contributors to non-uniform conversion coatings and poor corrosion resistance. This study implements a strategy aimed at regulating surface chemical composition and equalising interfacial potential differences to develop an Al-Mg-V chemical conversion coating on AZ91 magnesium alloy. The surface characteristics and corrosion resistance of the coating are investigated. The results demonstrate that the coating integrates the discretely distributed intermetallic compounds (Mg17Al12) into a continuous and stable cathode phase. The framework structure composed of Mg and Al effectively equalises the interfacial potential differences, reducing the potential difference from 300mV to 40mV. The coating enhances the polarization resistance of the AZ91 substrate by approximately 400 times and reduces the self-corrosion current density by three orders of magnitude. After a 186-hour neutral salt spray test, no corrosion is observed. The corrosion inhibiting structure formed by V hydroxides/oxides fill the pores and acts as a passivator on the surface, and imparts self-repair capabilities to the coating. The design concept of this chemical conversion coating is expected to be applied to other alloy materials.

In-depth investigation of corrosion inhibition mechanism: Computational, electrochemical, and theoretical studies of vanillin meldrum’s acid on mild steel surface in 1 M HCl

Vanillin Meldrum’s acid (VanMA) was successfully synthesized and thoroughly examined using techniques like elemental analysis, FTIR, NMR, UV–Vis spectroscopies, and single crystal X-ray diffraction. It crystallizes in a triclinic crystal system under the P-1 space group. A quantitative analysis of the intermolecular interactions in the crystal structures was performed using Hirshfeld surface analysis, which reveals that H···H contacts are the most significant contributing 43.2 % and the O···H/H···O contacts contributing 36.2 % of the total Hirshfeld surfaces. VanMA proved effective as a corrosion inhibitor in 1 M HCl, demonstrating a 62.19 % inhibition efficiency at an optimal concentration of 0.1 mM. It creates a protective layer on mild steel surfaces, adhering to the Freundlich adsorption isotherm (R2 = 0.9983) and displaying a physical adsorption mechanism (−12.72 kJ/mol). The corrosion inhibition efficacy of VanMA (0.1 mM) decreases in 1 M HCl as the temperature increases from 303 to 383 K. A shift towards physisorption is indicated by the increase in activation energy (Ea) from 12.37 to 16.42 kJ/mol. VanMA’s adsorption efficacy reduces at higher temperatures, increasing surface exposure and corrosion rates, but increasing activation enthalpy (ΔH° = 31.32 kJ/mol) and ΔS° = −113.63 J mol−1 K−1). The diameter of the semicircle rose as the concentration of VanMA increased, indicating that VanMA adsorption is responsible for the mild steel surface’s greater resistance to corrosion with increasing Rct values from 224 to 641 Ω cm2 and decreasing capacitance double layer (Cdl) values from 4.480 × 10−5 to 1.560 × 10−5 μFcm2, confirming VanMA’s efficacy as a corrosion inhibitor at 65.05 %. The SEM-EDX and AFM images show the smoother mild steel surface at 0.1 mM VanMA. VanMA was verified as a mixed-type inhibitor by showing shifts of less than 85 mV with respect to the blank PDP. The inhibition efficiency (IE%) increased up to 77.89 % while the icorr values decreased to 1.1850 × 10−5 A/cm2 as the VanMA concentration rose. In XPS, the presence of VanMA was identified by the presence of FeO (713.60 eV) and CO (287.93 eV), which signifies the adsorption of VanMA onto mild steel by the O atom and the negatively charged O ion via a mixed adsorption. DFT and Mulliken population analysis deduced that the VanMA interacted with the mild steel through mixed adsorption. VanMA adsorbs almost parallel to the Fe (1 1 0) surface, forming a barrier that protects from corrosion, according to the MD modeling. While the significant negative adsorption energy (−309.490 kcal/mol) verifies the stability and spontaneity of the adsorption process.

Bioresorbable composites based on magnesium and hydroxyapatite for use in bone tissue engineering: focus on controlling and minimizing corrosion activity

A biodegradable matrix with a significant content of bioactive components can be applied for bone tissue replacement, including load-bearing applications in orthopedic surgery. The study outlines the optimized procedure for the production of bioresorbable magnesium-hydroxyapatite (Mg-HA) composites and their corrosion resistance properties. Composites were meticulously crafted by combining pure magnesium with microwave-synthesized hydroxyapatite nanopowder. Sintering occurred via spark plasma sintering technology (SPS). To align the degradation time of the resulting composites with bone remodeling, the corrosion resistance of SPS materials was enhanced through the application of plasma electrolytic oxidation (PEO) and polycaprolactone (PCL) spin-coating methods. The protective properties, morphology dynamics, and composition due to surface treatment and corrosion propagation were investigated using Electrochemical Impedance Spectroscopy (EIS), Potentiodynamic Polarization (PDP), hydrogen evolution tests, Scanning Electron Microscopy (SEM), Energy-dispersive X-ray (EDX) as well as X-ray diffraction (XRD) analysis. Analytics of the physicochemical properties data of the formed coatings indicate a significant improvement in protective characteristics and deceleration of the corrosive degradation of the samples. The application of polycaprolactone to the PEO coating leads to a decrease in the corrosion current compared to uncoated magnesium composites by more than three orders of magnitude: from 1 10-5 to 2 10-9 A cm-2. During long-term exposure of samples to 0.9 % NaCl solution, it was found that coating reduced the rate of corrosion degradation of samples from 1.5 to 80 times compared to an unprotected Mg-HA composite and sintered magnesium. Mg-HA composites treated with PEO exhibit potential application as bioactive and biodegradable materials for orthopedic implants and fixation devices.

Optimized strategy for induction cladding of diamond/Ni-based wear-resistant coatings

Diamond/Ni-based wear-resistant coatings were fabricated on 45 steel using induction cladding, followed by laser remelting of the gradient coatings. The microstructure, phase composition, hardness, and friction properties of the coatings were examined. Results revealed that the surfaces of the composite and gradient coatings primarily consisted of a hard γ-Ni matrix and phases such as diamond, Cr7C3, and Cr23C6. High-temperature diffusion results in a strong metallurgical bond between the coating and the substrate. The gradient coating design significantly reduce the physical property mismatch between the 45 steel substrate and the composite coating. While laser remelting increased chromium aggregation and achieved a more uniform distribution of Fe, Ni, and Si. XRD analysis indicated that the Ni2Si diffraction peaks disappeared. Concurrently, the surface roughness and wear loss of the coating decreased, while the microhardness of the surface layer increased to 1030.74 HV, enhancing surface wear and corrosion resistance performance.

Effect of Oxidation Temperature on Surface Oxide Film Structure and Corrosion Resistance of 50 Steel

Effect of Oxidation Temperature on Surface Oxide Film Structure and Corrosion Resistance of 50 Steel

Development of Ti-Zr-Nb-Ta-Ag high entropy alloy for dental implants: In vitro corrosion behavior, antibacterial effect, and surface characteristics

This study presents a new biological high-entropy alloy (Bio-HEA) composed of 35Ti-35Zr-20Nb-5Ta-5Ag (at. %) for potential dental implant applications. The Bio-HEA underwent processing for various durations of mechanical alloying, followed by compaction and sintering. The processed Bio-HEA was tested for corrosion resistance in an artificial saliva medium, antibacterial properties, and surface characteristics. Surface topography and wettability were investigated using atomic force microscopy, surface profilometry, and contact angle measurements. Mechanical alloying, X-ray diffraction, and scanning electron microscopy revealed the formation of a solid-solution Bio-HEA with body-centered cubic crystal structures, with phase variations depending on the processing conditions. The Bio-HEA exhibited significantly higher microhardness values (4.38 GPa and 5.35 GPa) than commercial pure titanium (CPTi) and Ti-6Al-4V alloy, respectively. An increased ball-milling time resulted in higher microhardness for Bio-HEA and enhanced in vitro corrosion resistance in artificial saliva compared to CPTi. This was evidenced by a significant nobler shift of approximately 200 mV in the corrosion potential, with a prominent decrease of approximately two orders of magnitude in the corrosion current density and a higher charge transfer resistance. Additionally, the Bio-HEA demonstrated a lower contact angle compared to that of the Ti-6Al-4V alloy and CPTi. The Bio-HEA achieved antibacterial efficiencies of 91.76 % and 93.0 % compared to Ti-6Al-4V alloy and CPTi, respectively. The enhanced microhardness, antibacterial properties, in vitro corrosion resistance in artificial saliva, and wettability of Bio-HEA compared to commercial Ti-6Al-4V alloy and CPTi makes it a promising candidate for dental bioimplant applications.

Enhancing Corrosion Resistance of Mild Steel with a Hybrid Surface Coating: Film-Forming Zinc Titanate/Oleic Acid Composites

Coatings made from ceramic materials have shown remarkable effectiveness in preventing surface corrosion on mild steel surfaces. The coating's stability was enhanced by incorporating various elements into the matrix. This study incorporated an organic fatty acid, specifically oleic acid, into the zinc titanate. It forms a ZT/OA hybrid film-like coating on the MS surface. The synthesized ZT/OA nanomaterials were thoroughly characterized using PXRD, FT-IR, and SEM. The cubic spinel structure of ZnTiO3 and its spherical morphology were revealed from these techniques. The ZT/OA composites were applied to the surface of mild steel, and a film was formed under ambient conditions at a temperature of 150°C. An investigation was conducted on the electrochemical corrosion behaviors of ZT/OA composites in three electrode systems using both saline and acidic mediums. This study involved measuring the impedance and Tafel polarization corrosion data. The results indicate that the ZT40 (60 wt% oleic acid-doped) sample Showed a significantly higher resistance of 37638 Ω cm2, coupled with an impressive inhibition efficiency of 99.3% under saline conditions. Furthermore, under acidic conditions, the ZT40 sample exhibited excellent performance, as evidenced by the results of 691 Ω cm2 and 97% inhibition efficiency.

Machining-Induced Damage and Corrosion Behavior of Monel-400 Alloy Under Cryogenic Cooling Conditions: A Sustainable Initiative

AbstractMonel-400 is a nickel-based heat-resistant superalloy (HRSA) that is primarily used in oil and marine applications. Machining Monel-400 alloy for marine applications usually involves drilling and milling operations for assembly purposes, which should meet the requirements to withstand use in salt-water environments (i.e. lower surface finish to reduce corrosion and lack of burrs for tight sealing between mating parts). However, drilling of Monel-400 alloy can be challenging due to its high strength and density, which induces thermal effects that can influence the surface and geometrical integrity of the holes. Consequently, the use of environmentally friendly cooling technologies, such as cryogenics, is an excellent alternative to mitigate these effects, something which has not been widely investigated in the open literature when drilling Monel-400 alloy. Therefore, the current study aims to investigate the machinability of Monel-400 alloy under dry and cryogenic cooling conditions. The effects of cutting parameters and the use of a cryogenic liquid nitrogen bath on the surface integrity and corrosion resistance of holes were evaluated. Additionally, cutting forces, chip formation, and corrosion performance were analyzed. The results showed that the cutting forces increased by up to 8% under cryogenic cooling. Under cryogenic conditions, reduced elastic deformation resulted in a smaller chip size. Both cutting conditions produced a smooth surface finish with a roughness value of less than 0.2 µm. Corrosion resistance was reduced under cryogenic conditions at spindle speed of 5000 rpm. The current work showcases that cryogenic cooling is recommended for drilling Monel-400 alloy used in marine applications, but care should be taken in employing optimal cutting parameters to mitigate any effects on corrosion resistance.

Applicability evaluation technology for steel small diameter pipes containing external surface corrosion defects

With the continuous operation of oil and gas stations and petrochemical equipment, it has been found that steel small bore pipelines have different degrees of corrosion defects, which have led to pipeline cracking and medium leakage, and have increasingly attracted great attention of their oil and gas and chemical enterprises. In order to ensure the safe operation of the small diameter pipes with external surface corrosion defects, the influence law of the size of corrosion defects on the bearing capacity of the small diameter pipes were studied by finite element analysis and test simulation method, and the damage mechanism and failure form were analyzed, and the failure pressure prediction formula of the small diameter pipes with defects was fitted. It provides technical guidance for the applicability evaluation of corrosion-containing steel small diameter pipes in oil and gas chemical stations or installations.

Bio-inhibitive corrosion effect of carica papaya leaf extract on cold-rolled mild steel in 0.1 M HCl solution

Plant extracts are prone to microbial growth that can lead to microbial-induced corrosion (MIC), a major setback for their performance and stability as corrosion inhibitors. Hence, this work aims to identify the microbes that may cause the ineffectiveness of carica papaya leaf extract (CPLE) as a bio-corrosion inhibitor of cold-rolled mild steel in 0.1 M HCl solution for 48 days at 28℃. Cold-rolled mild steel coupons were immersed in 100 ml of 0.1 M hydrochloric (HCl) acid solution containing 1 g, 2 g, 3 g, 4 g, and 5 g of carica papaya leaf extract (CPLE) for 48 days at 28℃. The gravimetric method was used to determine the coupons' corrosion rate (CR), surface coverage, and inhibition efficiency (IE%) of the CPLE. The functional groups in the CPLE were identified using Fourier Transform Infrared Spectroscopy (FTIR), and the surface appearance of the coupons after immersion was examined using an atomic force microscope (AFM). Gravimetric data showed the coupons dipped in a 0.1 M HCl solution containing 3 g/100 ml of the inhibitor exhibited the highest inhibition efficiency of 87.73%, surface coverage of 0.88, and lowest corrosion rate of 0.00255 mm/day or 0.93 mm/yr, after 48 days at 28℃. In FTIR, transmittance peaks occurred at 1558 cm−1 for amines (-NH) in alkaloid scissoring, 1452 cm−1 for aromatic -C = C in flavonoids, 2932 cm−1 for aliphatic methylene (-CH2) and aldehyde (RCOH) stretching, 1035 and 1077 cm−1 for aromatic-OR in tannin, and 3280 cm−1 for out-of-plane bending of hydroxyl (-OH) in phenolics. Vitamin C (522,940 μg/g), flavonoids (860 μg/g), saponins (637.9 μg/g), terpenoid (48.4 μg/g), phenol (120%μg/g), alkaloid (4.18 μg/g), tannin (59.84%), and glycosides (9.04%) make up the extract's average phytochemical content. AFM presents pits and ridges on the mild steel coupons immersed in 0.1 M HCl solution without the extract. Those immersed in the solutions with varying concentrations of the extract had a passive layer of the CPLE adhering to the surfaces of the coupons thereby preventing the coupon’s direct contact with the acid solution and weight loss. However, over time, microbial growth decreased the efficiency of CPLE due to metabolites. Microbial tests show creamy, irregular and raised bacterial total colony-forming units per gram (Tcfu/g) as 4.6 × 105 Tcfu/g and 1.9 × 107 Tcfu/g in 2 runs. Also, a mixture of white and fluffy appearance and spore formation of fungi population of 4.8 × 105 Tcfu/g and 3.2 × 107 Tcfu/g in 2 Runs made up of Penicillium spp, Coccidioides immitis, Aspergillus flavus, and Fusarium spp, with hyphae, were seen in the solutions containing CPLE.

Influence of Al2O3 and h-BN on Wear and Corrosion Performance of IN625 Nickel-Based Coating

IN625 offers high-temperature oxidation resistance, wear resistance, and stable chemical properties. To improve the corrosion and wear resistance of the Q345B steel surface, two types of metal matrix composites (IN625 + 1% Al2O3 and IN625 + 1% h-BN) were applied to the substrate surface using the laser cladding process. This study analyzed the hardness, electrochemical corrosion, friction, and wear properties of both the laser-clad specimens and the substrates. The results show that (1) the hardness and wear resistance of the fusion-coated coating were significantly improved compared with the base material. Notably, the hardness increased by 19%, and the coefficient of friction decreased by 41% compared with the IN625 + 1% h-BN coating. Furthermore, the hardness and wear resistance of the IN625 + 1% h-BN coating were superior to those of the IN625 + 1% Al2O3 coating, attributed to the formation of eutectic compounds such as NiB and Ni2B in the dendritic region. (2) The corrosion resistance of the IN625 + 1% Al2O3 coating exceeds that of the IN625 + 1% h-BN coating and is also superior to that of the substrate. This improvement is primarily attributed to the addition of Al2O3, which enhances solid solution strengthening within the dendritic crystals of the fused-coating layer, reduces the percentage content of inclusions, and elevates the corrosion resistance of the coatings.