Papers by Keyword: Corrosion

Abstract: For solar collectors to be more durable and effective in renewable energy applications, surface enhancement is essential. The limited hardness and wear resistance of conventional aluminum alloys, including Al-6063, impair their long-term performance. By employing the pulsed laser deposition (PLD) technology to produce AlO₃ nano-coatings, this study seeks to overcome these constraints. The goal of this research is to use nanostructuring to improve the mechanical characteristics, resistance to corrosion, and optical performance of solar collectors. The surface of the solar collector alloy was coated with a nano- material (Al2O3) that had a particle size of 30 ± 5 nm. An Al2O3 nano material coating's micro-structure, phase composition, and effects were examined. PLD was applied to reduce erosion and corrosion and improve the mechanical performance of the aluminum alloy (AL-6063) used on the solar collector's surface. Using PLD, a 10 μm layer of aluminum dioxide was applied to the aluminum alloy's surface to ensure high hardness and a long fatigue life. Hardness testing on the samples showed an improvement in the alloy mechanical characteristics. Before and after deposition, an energy-dispersive X-ray spectroscopy test was carried out. The mechanical characteristics improved after an Al2O3 Nano layer was deposited. The samples' hardness increased from 626 HLD to 672 HLD, and erosion and corrosion decreased. Because of the Nano layer applied via PLD, the atomic percentage of oxygen deposited on the surface of the solar collectors changed between 8.3% and 9.4%, the roughness (x) decreased from 738 µm to 309 µm and the reflection ratio decreases. These outcomes confirm that PLD-deposited Al₂O₃ coatings improve the durability and efficiency of solar collectors, offering a promising solution for future renewable energy systems.

Abstract: This study evaluates the effect of temperature variations on the corrosion rates of A106 Grade B steel using dynamic polarization and weight-loss methods. Carbon steel samples were immersed in a 1-molecular-concentration hydrochloric acid electrolyte solution at different temperatures ranging from 25 to 55°C, with or without inhibitors at different concentrations, for a specified period. In this study, nano silica was synthesized in the laboratory using a Sol-gel process to serve as an environmentally friendly corrosion inhibitor derived from natural sand (Najaf, Iraq). The results demonstrate the effectiveness of the inhibitor, producing favorable corrosion rates even at high temperatures in its presence, while corrosion rates decreased in the absence of added inhibitor concentrations (400–1000 ppm). The results and statistical data were analyzed using Tafel and CR plots, Arrhenius analysis (ln (CR) vs. 1/T), and percentage inhibition ratios. Corrosion rates, current densities, and Tafel constants (CR, icorr., βc, βa) were determined during polarization, while the weights of the inhibitor-treated and non-inhibited samples were evaluated during weight loss studies. Tests (XRD, FTIR, AFM, TGA/TDS, and SEM) demonstrated the achievement of the work goal of developing a protective silicate layer of silica (SiO₂) nanoparticles, which provided effective and durable protection of the target metal surface samples from corrosion, especially under temperature fluctuations.

Abstract: This study examines the fabrication and performance of hydrophobic copper and nickel foams produced via a two-step immersion coating method using silver nitrate and stearic acid, targeting oil–water separation and corrosion protection in marine-related environments. In both substrates, silver deposition generated hierarchical surface roughness, while stearic acid functionalization reduced surface energy. Surface morphology and coating integrity were analyzed using scanning electron microscopy (SEM), and wettability was evaluated through water contact angle measurements. Copper foams exhibited water contact angles approaching 180°, demonstrated improved coating adhesion and separation efficiency remained above 95 % over repeated use. Copper-based superhydrophobic foams also showed excellent thermal and chemical stability, maintaining hydrophobicity after prolonged exposure to harsh conditions. Nickel foams developed a strongly adhered hydrophobic silver coating with water contact angles of approximately 147°. The coatings maintained high hydrophobicity across a wide temperature range and exhibited excellent reusability, achieving oil–water separation efficiencies higher than 95 % after multiple cycles. Potentiodynamic polarization was employed to evaluate corrosion behavior of both coated substrates in 3.5 % NaCl solution. Overall, the results indicate that while the same coating effectively provides hydrophobicity and durability to both copper and nickel foams, differences in wettability and coating stability are determined by their intrinsic microstructures.

Abstract: Nickel-Aluminium Bronze is a copper alloy with excellent corrosion resistance in marine environments. However, there are also applications of NAB in freshwater and corrosion phenomena have been observed in such cases. To explore the effect of microstructure on the corrosion behaviour, heat treatments were applied to NAB samples, which were corrosion tested in electrolytes with a composition typical for freshwater. Depending on the presence of bicarbonate, sulfate, and chloride, different kinds of corrosion attack were observed. The mayor effect lies in minimization of the β-phase amount and increasing the portion of a- and κ-phases. Corrosion promoted by sulfate is the major hazard in fresh water, while the passivating effect of bicarbonate supports localization of the attack. Chloride plays an ambivalent role; it promotes the corrosion attack but limits the progressively penetrating evolution of localized corrosion. Since the composition of freshwater has a stronger impact on the corrosion phenomena of the NAB alloy, the influence of the heat treatments is not clearly evident. Compared to seawater, heat treatments have a lesser effect on the corrosion behaviour in freshwater.

Abstract: Final turning, which is a finishing process for obtaining components with specific precise parameters, affects the integrity of the surface and its properties, whether hardness or surface residual stresses. The synergistic effect of these factors affects the susceptibility of the material, to stress corrosion cracking. In this work, 2 types of austenitic stainless steel, namely AISI 304 and AISI 321, were turned. Tool with positive cutting geometry was used for turning. The cutting parameters that varied were the cutting speed (100 and 250 m.min⁻¹) and the tool feed (0.12, 0.2 and 0.3 mm·rev⁻¹). The depth of cut was the same for all turnings (0.8 mm). Subsequently, the prepared samples were exposed in MgCl₂ solution based on the ASTM G36 for 96 hours. After this time, the samples were analysed using SEM, where the density of surface cracks was monitored. When comparing the crack density, an increase in density was visible for AISI 304 compared to AISI 321. It was shown that with increasing cutting speed, the density of cracks increased significantly, as well as with increasing tool feed. On the cross-sections the depth and length of the cracks were analysed. Crack depth and length increased with increasing feed too.

Abstract: Face-centered cubic (FCC) medium-entropy alloys (MEAs) are known for their excellent ductility and fracture toughness, but they suffer from relatively low mechanical strength. Alloying elements are added in FCC MEA matrix to promote the formation of hard secondary phase or intermetallic compounds that improve the mechanical performance of the alloys. In this study, the effect of chromium (Cr) and niobium (Nb) additions on the microstructural and corrosion characteristics of the CoNiV MEA matrix was investigated. A scanning electron microscope coupled with energy dispersive spectroscopy was used to analyse the microstructure and composition of the developed alloys. The corrosion properties of the alloys were evaluated using linear polarization. The alloys exhibited a dendritic microstructure with the presence of secondary phases, which is consistent with slow cooling associated with arc melting and the presence of elements with large atomic radii that upset the crystal lattice. Alloy containing Cr possessed better anti-corrosive properties than its Nb counterpart, signalling formation of a more stable Cr₂O₃ passive film. This layer creates a boundary between the corrosive medium and the alloy substrate to prevent further interaction.

Abstract: Austenitic stainless steels (ASSs) are characteristic with a combination of good mechanical and corrosion properties. Therefore, they are used in the primary circuits of nuclear power plants. Under the influence of a corrosive environment containing chloride ions and mechanical loading, the phenomenon of stress corrosion cracking occurs in ASSs. SCC can also be initiated by the surface condition of ASSs. Machining is usually the last stage of production, during which a significant deformed zone with high residual tensile stresses can be created, which can accelerate the initiation of stress corrosion cracking. Research is focused on analyzing the influence of final turning on microstructural changes of the surface-machined layer caused by various turning parameters (e.g.: cutting speed, feed, depth of cut, cutting tool geometry). No significant microstructure changes were observed between the samples by light microscopy, so we focused on transmission electron microscopy (TEM) on thin lamellas prepared using the focus ion beam (FIB) technique. TEM observation confirmed the presence of a deformed zone and a passivation layer. In the case of the sample that was turned with a higher feed and cutting speed, the passivation layer was discontinuous. Such a microstructural change can significantly affect the corrosion resistance of ASS.

Abstract: The paper summarizes the results of the analysis made on the ruptured tube of the reactor made of austenitic stainless steel in which the conversion of aniline to diphenylamine occurs at elevated temperature and pressure and in the presence of a catalyst. The tube wall perforation occurred in the piping used to measure the pressure in the reactor and a fire occurred after an aniline, ammonia and catalyst vapour leak. The material analyses carried out clearly showed that the thinning and subsequent perforation of the tube wall was due to a specific corrosion attack, so-called metal dusting, which occurs at elevated temperatures and in the presence of a carburizing atmosphere.

Abstract: In this research work, Ni rich superelastic Nickel-Titanium(NiTinol) alloy rods were joined using a fully automated direct-driven rotary friction welding machine at 1900 rpm. Samples were subjected to heat treatment after the removal of flash bead. Corrosion behavior of the NiTinol samples were carried out using weight loss method and Potentiodynamic Polarization (PDP) technique using 3.5% NaCl and 1N HCl solution in interval of 12h, 24h, 36h, and 48h at different temperature conditions such as 25°C, 35°C, 45°C, and 55°C respectively. Research has been carried out to find the corrosion characteristics for both annealed and cryogenically treated samples. Research findings revealed that, in weight loss method the impact of corrosion has no effect in the welded zone. In PDP method, the corrosion rate is found to be less and insignificant compared to any other alloys. Hence, the material proved as anti-corrosive in nature. This fact is due to the formation of Titanium oxides (TiO₂) and Titanium nitrides passive layers which hinders the rate of corrosion. However, more corrosion resistance was seen in cryogenically treated welded samples compared to the other samples.

Abstract: Corrosion of steel structures in marine environments is a critical issue affecting infrastructure integrity and maintenance costs worldwide. Generally, inhibitors have proven to reduce the corrosion rate to the barest minimum than other methods. The inhibitors are produced using the experimental method which is time consuming and costly. This necessitate the development of models for the quick assessment of the efficiency of the inhibitor. This research focused on the prediction of corrosion inhibitory efficiency of water hyacinth on mild steel in marine environment using multiple linear regression (MLR) method. Various concentrations (5 ml, 10 ml, 15 ml, 20 ml and 25 ml) were added to the samples immersed in seawater and a sample without the addition of the inhibitor was used as the control for a period of 30 days. The study was carried out using weight loss method and the corrosion rate as well as the inhibition efficiency were calculated. Phytochemical analysis and atomic absorption spectroscopic were carried out on the inhibitor while Scanning Electron Microscopy and Energy Display X-ray Spectroscopy were used to analyze the steel sample. The analysis of the result showed that the best inhibition efficiency obtained was 90% and this was achieved with 15% concentration of the inhibitor. Multiple linear regression model was developed to predict the inhibitor’s efficiency. The predicted efficiency with the MLR model was compared with that of the experimentally obtained efficiency and the outcome shows a conformity between the experimental and the predicted value. It would therefore be recommended to rely on multiple linear regression in predicting the efficiency of water hyacinth for corrosion control of mild steel in marine environment based on the closeness of the predicted values to the experimental values.