Papers by Keyword: Corrosion

Abstract: This research is centered on an environmentally sustainable sol-gel coating, using silica extracted from rice husk ash (RHA), to foster the persistent deterioration of mild steel cause by corrosion for decades despite all efforts put in place by previous researchers. The research focus, was on the extraction of silica from rice hush to synthesize silica-base sol-gel formulation, doped in a graphene oxide to enhanced its efficiency. The formulated sol-gel coating was applied on the mild steel substrates and then characterized by evaluating its corrosion resistance through electrochemical and surface characterization techniques. Such as XRD, FT-IR, SEM, Tafel Polarization and Adhesion Test, which were carried out on the coated samples. Corrosion test was carried out by immersing coated and uncoated samples in 3.5% NaCl solution for seven (7) days and then conducted a Potentiodynamic polarization and Electrical Impedance Spectroscopy (EIS) test to analyze the corrosion rates, impedance and protection efficiency. It was observed that, the highest inhibition efficiency of 85% was achieved at a concentration of 1.0g/200ml after 7 days of exposure which revealed that, coated mild steel possess higher potential corrosion resistant when compared with the conventional anti-corrosion coating in use. Essentially, this research would definitely promote green chemistry by utilizing agricultural waste materials, avoiding uses of toxic precursors and offering an eco-friendly alternative to conventional anti-corrosion coatings.

Abstract: AZ31 magnesium alloy is a representative magnesium alloy with well-balanced mechanical properties and castability. However, AZ31 magnesium alloy also has the disadvantage of poor corrosion resistance due to its low aluminium content. In previous research, it is known that the corrosion mechanism is such that filamentous corrosion is generated and then changes to full-scale corrosion. However, the relationship between corrosion and bending properties has not been revealed. In this study, AZ31 magnesium alloy was immersed in salt water with a concentration of 5%, and three-point bending tests were conducted to confirm changes in bending stress and strain due to strength loss caused by corrosion. Then, investigated which parameters Ra and Rz, which are indicators of surface roughness, are related to the maximum bending stress of the fully corroded AZ31 magnesium alloy. As a result, when evaluating the relationship between maximum bending stress and corrosion, it was found that it is better to evaluate by Ra of the corroded surface rather than by Rz.

Abstract: This work aimed to develop new S355-based structural steels with enhanced marine corrosion resistance while preserving mechanical properties. Two alloying strategies (Cu/Ni and Al/Cr) were investigated. Conventional and new steel samples were produced and characterized for microstructure, mechanical properties, and corrosion. The new steels showed similar or improved mechanical properties. Potentiodynamic polarization tests indicated stabilization of the oxidation process in the new steels. Laboratory accelerated corrosion tests on painted specimens revealed reduced blistering at paint film defects for some new steels compared to conventional steel. Ongoing research includes evaluating painted specimens in a real offshore environment using an advanced floating laboratory

Abstract: The effect of grain size on the initiation behavior of exfoliation corrosion in cold-rolled Mg-14mass%Li-3mass%Al alloy was examined. Exfoliation corrosion initiated after 30 minutes in the coarse-grained structure (279μm), whereas it was delayed to 60 minutes in the fine-grained structure (75μm) and further to 75 minutes in the ultrafine-grained structure (39μm). This delay is attributed to the suppression of shear band formation and localization during cold rolling with decreasing grain size, which enhances the uniformity of surface reactions in the corrosive environment and promotes faster and denser formation of the protective film at the early stage. Accordingly, the improved condition of the initial corrosion film is considered the primary factor responsible for the delayed onset of exfoliation corrosion.

Abstract: Cu and Ni impurities in Mg alloys are deleterious contaminants that reduce the corrosion resistance of the alloy. Mg₂Cu and Mg₂Ni precipitates can cause significant anodic dissolution of the Mg matrix, owing to their potential difference. Suppression of these phases can prevent the deterioration of corrosion resistance. The neutralization of these impurities through the formation of MgZn₂ intermetallic phases has been studied, because the atomic radii of Cu and Ni are similar to that of Zn. As a result, the MgZn₂ phase may precipitate during the rapid cooling that occurs during the solidification of the Mg-6 mass% Zn alloy, and introduce substitutional impurity atoms in the crystal lattice. Mg (Zn, Cu, Ni)₂ phase can be formed instead of Mg₂Cu and Mg₂Ni, in the presence of both of Zn and these impurities. In this study, the solubility of Cu and Ni into MgZn₂ phase when they contain simultaneously was investigated by preparing the intermetallic compounds and the crystal structure evaluation. The lattice parameter of the MgZn₂ phase containing both Cu and Ni impurity decreased to about 5.14 Å with increasing impurity concentration. Cu and Ni impurities are concentrated in the MgZn₂ phase while maintaining the crystal structure, when the impurity concentrations are within the composition range of Cu + 2Ni ≦ 20 at.%. When the concentrations of Cu and Ni exceeded this range, the crystal structure of the MgZn₂ phase transformed from hexagonal (hP12) to cubic (cF24).

Abstract: This study investigates plantain peduncle extract as a green corrosion inhibitor for AA6063 aluminium alloy in 1M NaCl using electrochemical techniques (OCP, LSV, Tafel analysis). Extract concentrations were tested at 30–50°C. Results showed concentration-dependent inhibition, with (0.3 ml) achieving maximum efficiency: 85.48% (30°C), 88.00% (40°C), and 89.92% (50°C). Tafel data confirmed reduced corrosion rates (0.18–0.13 mm/yr vs. control: 1.24–1.29 mm/yr) and increased polarization resistance (1.71–2.34 kΩ·cm² vs. control: 0.247 kΩ·cm²). OCP/LSV curves demonstrated cathodic potential shifts and suppressed current densities, indicating mixed-type inhibition. Langmuir isotherm analysis (R² > 0.994) confirmed monolayer adsorption, with ΔG_ads values (−64.32 kJ/mol at 30°C) suggesting chemisorption dominance. Optical micrographs revealed reduced corrosion with inhibitor concentration, though isolated pitting persisted. Empirical optimization (ANOVA) identified 0.144 ml at 30.1°C as optimal for minimal corrosion rate (0.21 mm/yr).

Abstract: In this study, researchers investigated the effectiveness of silver nanoparticles (AgNPs) combined with powder extracts from Moringa oleifera (Malunggay) for inhibiting corrosion on A36 mild steel, a common material used in the oil and gas industry. The synthesis process involved mixing AgNPs with Moringa oleifera extracts at different concentrations in acidic conditions and varying temperatures. Characterization techniques such as UV-Vis Spectroscopy, FT-IR, and TEM were used to analyze the structural and functional properties of the resulting Moringa-AgNPs. The study aimed to evaluate how these nanoparticles affected the corrosion resistance of A36 steel under different conditions, including temperature and inhibitor concentration, by assessing parameters like weight loss and corrosion rate. SEM/EDS analysis provided further insights. Overall, the research suggests that incorporating Moringa-AgNPs could be a promising strategy to reduce corrosion rates in the oil and gas industry.

Abstract: Conventional techniques for obtaining ligatures, ferroalloys, or modifiers are often associated with prolonged processing times, material losses, low energy efficiency, and environmental challenges. The self-propagating high-temperature synthesis (SHS) metallurgy method partially eliminates these drawbacks, allowing ligatures to be formed from hard- and soft-melting elements. The present work focuses on selecting a metallurgical technique for producing SHS complex ligatures in the Fe–Mn–B system, studying the structure and chemical composition of obtained ligatures, and evaluating their corrosion properties.

Abstract: Modern engineering components require composites that are robust, lightweight, and inexpensive as integrated particulate for solid strengthening and corrosion resistance alloy. This study envisions a snail shell particulate (SSP) as a potential biofillers on aluminium alloy due to its inherent characteristics. The fabrication of the developed alloy was done through liquid stir casting method with determination to examine the correspondent physical, optoelectrical, electrochemical, and microstructural behaviour for chemical application. Composite infringement varies from 10% - 25% SSP after optimization using design of experiment. The result of electrochemical analysis showed a notable decrease in corrosion rate with increased SSP content from 12.06 mm/yr, of control sample to (75Al-25SSP) which had a corrosion rate of 7.59 mm/yr, resulting in a 40.1% drop-in degradation rate. Notably, microhardness properties increase from 28.1 to 45.5 HRB as a result of solid strengthening characteristics of doped fillers. Opto-electrical assessment demonstrated decreasing resistivity with higher SSP content, indicating improved current flow resistance. The microstructural properties showcased SSP's distinctive dispersion with few micro pores. The intermetallic phases confirmed their integration into the metal matrix by providing an enhancing adhesion and solid crystalline structure.

Abstract: Nowadays, researchers are trying to understand whether geopolymers have the potential to be used as a coating material, particularly for protecting metal from corrosion attack. This study aimed to evaluate the effectiveness of fly ash-based geopolymer coatings in protecting steel by immersing the coated samples in a 3.5 wt% NaCl solution for immersion periods of 1, 7, 14, and 28 days. The uncoated steel showed the NaCl color changed to yellowish and became darker with increasing immersion time, indicating severe corrosion on the uncoated steel after 28 days. Surprisingly, with 3mm geopolymer thickness coated on the steel, NaCl solution remain unchanged until 28 days immersion period. The corrosion rate exhibits a very gradual increase, with only 0.112 mm/year recorded after 28 days of immersion. No defects such as blistering, peeling, or cracking were observed on the coated steel. These results indicate that geopolymer holds considerable promise as a coating material, warranting further investigation for its potential applications in this area.