Correlative investigation of the corrosion susceptibility of C70600 and C26000 copper based alloys for application in seawater environment

Appropriate selection of Cu based alloys for petrochemical, energy generation, desalination and piping applications in marine operating conditions is of utmost importance. Correlative investigation of the corrosion susceptibility of two Cu based alloys (C70600 CuNi and C26000 CuZn) was done with potentiodynamic polarization technique and open circuit potential analysis in 0.05 M H2SO4 solution at 0.5%, 1.5%, 2.5%, 3.5% and 4.5% NaCl concentration. The corrosion susceptibility of both alloys were generally similar at 0.5% (0.05 mm/y and 0.06 mm/y), and 1.5% (0.11 mm/y and 0.10 mm/y) Cl- ion concentration. Beyond 1.5% concentration C70600 proves to be substantially more corrosion resistant with optimal corrosion rate value of 0.74 mm/y compared to 2.68 mm/y for C26000 at 4.5% NaCl concentration due to variation in the constituent of the oxide layer precipitated on C70600 alloy which differs from C26000. C70600 exhibited dominant cathodic passivation and subsequent corrosion deterioration resulting in visible cathodic potential displacement. C26000, despite its relatively higher corrosion susceptibility underwent metastable pitting activity proportional to the Cl- ion concentration. Anodic passivation and selective dissolution of C26000 occurred following anodic polarization due to the presence of Zn in its outer matrix. Open circuit potential measurement shows Cl- ion concentration significantly influences the thermodynamic stability, passivation and corrosion resistance of the Cu alloys. However plot characteristics and potential readings showed C70600 to be more corrosion resistant and thermodynamically stable coupled with significantly lower tendency to corrode

Corrosion And Wear Resistance Of Titanium- And Aluminum- Based Metal Matrix Composites Fabricated By Direct Metal Laser Deposition

Titanium- and Aluminum-based metal matrix composites (MMC) have shown favorable properties for aerospace applications such as airframes, reinforcement materials and joining elements. In this research, such coatings were developed by direct metal laser deposition with a powder-fed fiber coupled diode laser. The MMC formulations consisted of pure titanium and aluminum matrices with reinforcing powder blends of chromium carbide and tungsten carbide nickel alloy. Two powder formulations were investigated for each matrix material (Ti1, Ti2, Al1 and Al2). Titanium based composites were deposited onto a Ti6Al4V plate while aluminum composites were deposited onto AA 7075 and AA 5083 for Al1 and Al2, respectively. Microstructures of the MMCs were studied by optical and scanning electron microscopy. The hardness and reduced Young\u27s modulus (Er) were assessed through depth-sensing instrumented nanoindentation. microhardness (Vickers) was also analyzed for each composite. The corrosion resistance of the MMCs were compared by monitoring open circuit potential (OCP), polarization resistance (Rp) and potentiodynamic polarization in 0.5 M NaCl to simulate exposure to seawater. The Ti-MMCs demonstrated improvements in hardness between 205% and 350% over Ti6Al4V. Al-MMCs showed improvements between 47% and 79% over AA 7075 and AA 5083. The MMCs showed an increase in anodic current density indicating the formation of a less protective surface oxide than the base metals

Characterization of the Anodic Film and Corrosion Resistance of an A535 Aluminum Alloy after Intermetallics Removal by Different Etching Time

Copyright © 2022 by the authors. The objective of this study was to improve the corrosion resistance of an A535 alloy by removing intermetallics on the alloy surface by alkaline etching to improve the morphologies and properties of the anodic film that was sealed with different sealants. It was found that alkaline etching for 4 min was suitable for dissolving intermetallic particles and simultaneously providing sufficient roughness for the adhesion of an oxide film to the Al matrix. The effect of alkaline etching revealed that a decrease in the intermetallic fraction from 21% to 16% after etching for 2 and 4 min, respectively, corresponded to the increase in the surface roughness, thickness, and consistency of the anodic film. It was also demonstrated that the surface morphology of the anodic films after stearic acid sealing was more uniform and compact than that after nickel fluoride sealing. The electrochemical polarization curves and salt spray test proved that the alloy etched for 4 min and sealed with stearic acid had better corrosion resistance as compared with the aluminum alloy sealed with nickel fluoride.This work was supported by the Research Strengthening of academic year 2563, the Project of Faculty of Engineering, King Mongkut University of Technology Thonburi year 2020

Corrosion resistance and passivation behavior of 3004 AlMnMg and 4044AlSi aluminum alloys in acid-chloride electrolytes

Corrosion resistance of 3004 and 4044 aluminium alloys (3004Al and 4044Al) in neutral chloride (0.5%–4.5% concentration), sulphate (0.00625M-0.1Mconcentration), and chloride-sulphate (0.00625MH2SO4/0.5%–4.5% chloride concentration) solutions was studied with potentiodynamic polarization, open circuit potential, cyclic polarization, and optical microscopy. Results show 4044Al exhibited higher resistance to general corrosion while 3004Al was more resistant to localized corrosion. Corrosion of 4044Al decreases with increase in chloride concentration while 3004 Al increases. Corrosion rate values for 3004Al and 4044Al in sulphate solution were generally similar between 0.061–0.395mmy−1 and 0.168–0.213mmy−1, respectively. In chloride-sulphate solution, corrosion rate of 3004Al increased from 0.130mmy−1 to 1.563mmy−1 at peak chloride concentration whereas the corrosion rate of 4044Al is near constant. The passive film on 4044Al is found to weaken significantly with increase in chloride concentration. Passivation values varied from 0.39 Vat 0.5% chloride concentration to 0.01 Vat 4.5% concentration while the potential at which stable pitting occurred increased. The passivation range values for 3004Al are relatively stable with respect to chloride concentration. Results from cyclic polarization experiments show the deterioration rate of both alloys in NaCl solution is subject to chloride concentration. The results show the alloys corrode at all NaCl concentrations (0.5%–4.5%) with the lowest pitting corrosion risk in 0.5% and 1.5%NaCl solutions. The highest pitting corrosion risk of the alloys occurred in 3.5% NaCl solution. Significant localized morphological deterioration is visible throughout the entirety of 4044Al relative to the adjacent Al alloy matrix compared to total surface deterioration on 3004Al

Brazing filler metals

Brazing is a 5000-year-old joining process which still meets advanced joining challenges today. In brazing, components are joined by heating above the melting point of a filler metal placed between them; on solidification a joint is formed. It provides unique advantages over other joining methods, including the ability to join dissimilar material combinations (including metal-ceramic joints), with limited microstructural evolution; producing joints of relatively high strength which are often electrically and thermally conductive. Current interest in brazing is widespread with filler metal development key to enabling a range of future technologies including; fusion energy, Solid Oxide Fuel Cells and nanoelectronics, whilst also assisting the advancement of established fields, such as automotive lightweighting, by tackling the challenges associated with joining aluminium to steels. This review discusses the theory and practice of brazing, with particular reference to filler metals, and covers progress in, and opportunities for, advanced filler metal development

Design and development of highly efficient nano fluidic flat plate solar collector

The increase in demand for energy along with the depletion of conventional energy sources requires the improved utilization of renewable energy resources. Moreover, the unfavourable response of existing energy urges to take necessary action rapidly. Therefore, it is desired to generate an alternative source of energy or renewable energy for the industries. Among all renewable energy resources, solar energy is the most advantageous alternative to conventional energy sources owing to its inexhaustibility and green property. Generally, solar energy is harvested using different solar collectors. Solar collectors are devices that convert solar radiation into heat or electricity. However, the efficiency of the solar collector specifically flat plate solar collector is still not adequate. Thus, to form an optimum designed of a flat plate solar collector and by reintroducing the working fluid with the new transport medium; the efficiency of the collector can be improved. The competent step to enhance the efficiency of the solar collector is to redesign the flat plate solar collector considering the number and diameter of the header and riser tubes of flat plate solar collector. Secondly, replacing the working fluid inside the header and riser tubes with ethylene glycol-based Al2O3 and CNC nanofluids flowing through them. And finally, analysing the thermal performance of these new transport mediums in flat plate solar collector. This study is carried out in different phases viz. computational numerical simulations to design flat plate solar collector; measurement and evaluation of distinctive thermo-physical properties of Al2O3 and CNC nanofluids including stability, thermal conductivity, viscosity, specific heat, density and pH; implementation of nanofluids in the solar collector and finally, numerical simulation based on the experimental design and experimental properties of nanofluids. Experiment executed with a fixed flow rate and in the steady-state condition under solar irradiation. In results, the optimum 8-23-12 (number of riser tubes-diameter of header-diameter of riser) design of header and riser tubes of solar collector selected based on the statistical analysis of numerical simulations. From the thermo-physical point of view, thermal conductivity increased in a maximum of 13.4% and 11.5% for Al2O3 and CNC nanofluids respectively. Furthermore, the highest of 36% and 19% viscosity obtained with the augmentation of Al2O3 and CNC nanoparticle into the base fluid at 30oC temperature respectively but decreased with the raising of temperature. Moreover, decrement of specific heat occurred due to an increment of volume concentrations of nanofluids. However, specific heat capacity enhanced by the progressive gradient of temperature. On the other hand, contraction of the density of nanofluids obtained with an improvement of temperature and of 3.8% decreased in maximum at 80oC temperature. Al2O3 nanofluids showed the pH range of 2 to 4 and CNC nanofluids were within 5 to 7.5 scale of pH. The experimental study has implied that up to 2.48% and 8.46% efficiency of solar collector enhanced by using 0.5% Al2O3 and 0.5% CNC nanofluids respectively. And the most significant result is that of about 5.8% efficiency can be improved in flat plate solar collector by CNC/water-EG nanofluid. In addition, all types of nanofluids performed better convection heat transfer and quick heat diffusion characteristics with laminar fluid flow behaviour. Applying CNC/water-EG nanofluid enhances the efficiency of a flat-plate solar collector to consume the limitless solar energy to create an alternative source of energy for the industries

Advances in Laser Materials Processing

Laser processing has become more relevant today due to its fast adaptation to the most critical technological tasks, its ability to provide processing in the most rarefied and aggressive mediums (vacuum conditions), its wide field of potential applications, and the green aspects related to the absence of industrial cutting chips and dust. With the development of 3D production, laser processing has received renewed interest associated with its ability to achieve pointed to high-precision powder melting or sintering. New technologies and equipment, which improve and modify optical laser parameters, contribute to better absorption of laser energy by metals or powder surfaces and allow for multiplying laser power that can positively influence the industrial spread of the laser in mass production and advance the existing manufacturing methods. The latest achievements in laser processing have become a relevant topic in the most authoritative scientific journals and conferences in the last half-century. Advances in laser processing have received multiple awards in the most prestigious competitions and exhibitions worldwide and at international scientific events. The Special Issue is devoted to the most recent achievements in the laser processing of various materials, such as cast irons, tool steels, high entropy alloys, hard-to-remelt materials, cement mortars, and post-processing and innovative manufacturing based on a laser