Papers by Keyword: Corrosion

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.

Abstract: 17-4 Precipitation hardenable (PH) stainless steel (SS) is useful for applications that require a combination of high strength and corrosion resistance. However, when produced through selective laser melting (SLM), it has a distinct microstructure with significant composition and phase variations based on the process parameters and post processing heat treatment conditions. Therefore, the present study examines how process parameters, such as scanning speed and hatch distance, affect the microstructural, and corrosion characteristics of additively manufactured (AM) 17-4 PH stainless steel samples. Post-processing heat treatment resulted in a uniform and reproducible microstructure in SLM samples. Heat-treated AM samples were assessed in a 3.5 wt. % NaCl solution using electrochemical impedance spectroscopy (EIS). The specimen with an energy density of 39.06 J/mm³ exhibited the lowest open circuit potential value, indicating a favorable tendency to form a passive film. The sample with 66.96 J/mm³ exhibits enhanced corrosion resistance attributed to robust protective performance facilitated by a dense network of precipitates and finer grain size. This heightened resistance is further supported by the sample's highest corrosion layer resistance and charge transfer resistance.

Abstract: Plasma nitriding (ion nitriding) is a plasma-supported thermochemical cementation of steel, during which the hardness of the surface and resistance to wear and fatigue of the material increases due to the formation of a hard layer. The process of plasma nitriding is very variable, which makes it possible to nitride all types of steel, but the result depends primarily on the chemical composition and process tech-nique. In this way, for example, cement, construction, tool steels, high-strength and stainless steels, as well as cast iron, are nitrided. Structural steel belongs to a group of very important and diverse materi-als, it has versatile use in many areas of industry such as machines, vehicles, buildings, bridges, etc. Corrosion of materials is a common phenomenon that cannot be completely eliminated. This degrada-tion is often classified as one of the main reasons for material loss. The article presents the benefit of plasma nitriding on the corrosion resistance of structural steels. Experiments were carried out for select-ed three types of structural steels, on which plasma nitriding was performed and then a corrosion test in a mist of neutral sodium chloride solution. The achieved results confirmed that plasma nitriding has a significant effect on increasing the corrosion resistance of structural steels.

Abstract: Ti-6Al-7Nb is commonly used as orthopedic implant, especially for total hip arthroplasty application, due to its excellency in biocompatibility and surface feature. This study investigates the effects of varying solution treatment temperatures on the mechanical properties and corrosion resistance of the biomedical Ti-6Al-7Nb alloy fabricated using centrifugal investment casting. Solution treatment was performed at 850°C, 970°C, and 1050°C, and the results were evaluated through tensile tests, hardness measurements, microstructural observations, and potentiodynamic polarization tests. The treatment at 970°C produced the optimal combination of mechanical strength and corrosion resistance, achieving a tensile strength of 690 MPa and the lowest corrosion rate of 0.00826 mmpy. The superior performance at 970°C is attributed to the formation of fine α precipitates in the microstructure. These findings highlight the effectiveness of suitable solution treatment temperature in enhancing Ti-6Al-7Nb’s properties for potential use in biomedical applications.

Abstract: Developing titanium aluminides (Ti-Al) based alloys by means of Laser Engineered Net Shaping (LENS) in-situ manufacturing presents attractive properties as compared to other fabrication methods. Ti-Al alloys have attracted much attention for high-temperature performance in gas turbine and automobile applications because of their attractive properties such as low density, high strength, high stiffness, and good oxidation resistance. In this work, laser in-situ fabricated Ti-Al-Nb-Cr quaternary alloys were developed. The samples were exposed to 1350°C and cooled in air for stress relief and for homogenizing phase distribution before characterization, corrosion behaviour and oxidation properties were investigated. From the electrochemical performance results, sample QT1 and QT2 displayed high potential and high current densities with the values of-0.33931V, -0.36934V and 5.77E-05A/cm², 4.89E-05A/cm², respectively and the corroded SEM proves that the samples had minimal structural damage. The minimum mass gain was observed during oxidation test proving that Ti-Al-Nb-Cr alloys have outstanding oxidation properties for potential high temperature application.

Abstract: NbTiFeCrAl high entropy alloy was successfully fabricated on Ti-6Al-4V alloy substrate using laser cladding. The laser power was varied from 800 to 1200 W while the scanning speed was kept constant at 1.5 m/min. The results revealed that the coating possessed dendritic microstructure with BCC solid solution phases. The porosity and homogeneity of the coating were found to be dependent on deposit depth and laser power. The coating was also characterized by high microhardness but no improvement in corrosion resistance was established when compared with the substrate.

Abstract: Carbon steel is widely used in infrastructure, manufacturing, and structures due to its cost-effectiveness and robust mechanical properties. However, the susceptibility of steel structures to corrosion in various working environments has been a longstanding concern. In this study, we explored the potential of titanium-aluminum (Ti-Al) coating as a surface treatment to enhance the corrosion resistance of low-carbon steel. The coating was applied using the arc spraying technique, where two materials were melted by an arc and then distributed onto the substrate using compressed air. To evaluate the corrosion resistance of the coated samples, we conducted immersion tests following the ASTM G31 standard for durations of 625 and 1000 hours. Additionally, electrochemical technique was employed to assess the anti-corrosion performance of both the Ti-Al coating and the substrate. Surface characterization was carried out using scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDX), as well as measurements of hardness and roughness. The SEM-EDX analysis revealed uniform distribution of titanium and aluminum across the surface and within the coating. Moreover, the coating significantly altered the surface roughness. Electrochemical corrosion testing indicated that the Ti-Al coating exhibited lower corrosion current and corrosion potential, suggesting its potential to enhance the corrosion resistance of the substrate. The SEM-EDX revealed cracks on the coating surface and the oxidation level of the coating surface varied with immersion time. The hardness of the coating was found to be relatively lower than that of the substrate, while the surface roughness was higher. Overall, the findings suggest that Ti-Al coating holds promise for enhancing the corrosion resistance of steel structures, as evidenced by its low corrosion current density and corrosion potential in corrosive environments.

Abstract: The exceptional corrosion resistance, low weight, and high strength of titanium (Ti) make it an excellent choice for components in proton exchange membrane fuel cells (PEMFC). However, during PEMFC operation, Ti undergoes passivation, which diminishes the bipolar plates' (BP) ability to transport electrons between cells. Applying titanium nitride (TiN) coatings, known for their good conductive properties, can resolve this issue and enhance corrosion resistance. Additionally, using additive manufacturing (AM) to produce BP offers numerous benefits in terms of structural control for more intricate designs. This study examines the impact of TiN coating via gas nitriding on Ti-6Al-4V open structures created by powder bed fusion-electron beam/metal (PBF-EB/M) or PM routes, focusing on the surface characteristics such as composition and interfacial contact resistance (ICR).

Abstract: This study aimed to determine the effect of concentration and immersion time of Salak (Salacca zalacca) Seed extract as a green inhibitor on the corrosion inhibition efficiency and corrosion rate of AISI 1040 steel in a 1M HCl environment. The chemical composition of AISI 1040 steel was confirmed using OES testing to verify its compliance with AISI 1040 chemical standards. The antioxidant activity of the salak (Salacca zalacca) seed extract was determined through the 1,1-Diphenyl-2-Picrylhydrazyl (DPPH) test yielding an IC50 value of 192.55 ppm, indicating weak antioxidant activity. Qualitative phytochemical analysis confirmed the presence of flavonoids and tannins in the extract, as verified by Fourier Transform Infrared (FTIR) testing. The study explored concentration variations ranging from 100 to 500 ppm and immersion time variations of 10 to 30 days were used. The highest inhibition efficiency was obtained at 500 ppm concentration, while the lowest was at 100 ppm, with values of 40.26% and 18.90% respectively. Additionally, the corrosion rate was reduced to 0.035 mm/year at the highest concentration of 500 ppm. These findings demonstrated the potential of salak (Salacca zalacca) seed extract as an eco-friendly, effective corrosion inhibitor for AISI 1040 steel.