El-Sayed M. Sherif

The powder metallurgy method was used to manufacture three Ti-based alloys: Ti-15%Zr-2%Ta-4%Sn (Ti-Zr-Ta-4Sn), Ti-15%Zr-2%Ta-6%Sn (Ti-Zr-Ta-6Sn), and Ti-15%Zr-2%Ta-8%Sn (Ti-Zr-Ta-8Sn). Electrochemical measurements and surface analyses were used to determine the effect of Sn concentration on the corrosion of these alloys after exposure to a simulated body fluid (SBF) solution for 1 h and 72 h. It was found that the passivation of the alloy surface significantly increased when the Sn content increased from 4% to 6% and then to 8%, which led to a significant reduction in corrosion. The impedance spectra derived from the Nyquist graphs also explained how the addition of Sn significantly improved the alloys’ polarization resistances. According to the change in the chronoamperometric current at an applied anodic potential over time, the increase in Sn content within the alloy significantly reduced the currents over time, indicating that the uniform and pitting corrosion were greatly decreased. The formation of an oxide layer (TiO2), which was demonstrated by the surface morphology of the alloys after exposure to SBF solution for 72 h and corrosion at 400 mV (Ag/AgCl) for 60 min, was supported by the profile analysis obtained by an X-ray spectroscopy analyzer. It was clear from all of the findings that the tested alloys have a remarkable improvement in resistance to corrosivity when the Sn content was increased to 8%.

This study investigates the influence of 3 vol.% Al2O3, 3 vol.% TiO2, and 3 vol.% Y2O3 in the CrFeCuMnNi equimolar high-entropy alloy on its microstructural changes and corrosion resistance. These oxide-dispersed high-entropy composites (ODS-HECs) were synthesized via high-energy ball milling (50 h) followed by uniaxial hot-compaction (550 MPa, 45 min), medium-frequency sintering (1100 °C, 20 min), and hot forging (50 MPa). The microstructures of the developed composites produced a stable FCC phase, a small amount of ordered BCC-B2 structure, Fe2O3, and corresponding dispersed oxide phases. The corrosion of the developed high-entropy composites was tested in 3.5% NaCl solution using several electrochemical techniques. The results revealed that the corrosion rate (RCorr) decreased with the incorporation of oxide particles. Among the investigated samples and based on the electrochemical impedance spectroscopy results, CrFeCuMnNi-3 vol.% TiO2 ODS-HECs were seen to possess the highest value of corrosion resistance (RP). The change in the chronoamperometric current with time indicated that the CrFeCuMnNi alloy suffered pitting corrosion which decreased when Al2O3 was added, forming a CrFeCuMnNi-3 vol.% Al2O3 sample. In contrast, the incorporation of a 3 vol.% Y2O3, and 3 vol. TiO2, prevents pitting.

The current work is in continuation of our previous work where we reported changes in the properties of epoxy coatings using two different types of hardener in different stoichiometric ratios. The best results-oriented coating stoichiometry was then taken in this research for further modification with the incorporation of 1, 2 and 3 wt.% micro aluminium (Al) pigments designed for coating carbon steel panels. After 7 d of curing, the coated panels were characterized using X-ray diffraction (XRD), (SEM) scanning electron microscopy, (TGA) thermogravimetric analysis, pendulum hardness, a scratch test and nano-indentation. Electrochemical tests were carried out for various exposure periods of time, i.e., 1 h, 7 d, 14 d, 21 d and 30 d, in a 3.5% sodium chloride (NaCl) solution. For the coatings, we found that the presence of 1% Al provided the highest corrosion resistance after exposure periods in the NaCl solution. We also found that prolonging the immersion time decreases the corrosion resistance after 7 d, but increasing the time of immersion to longer periods (14 d, 21 d and 30 d) enhances the corrosion resistance and reduces the degradation of the coatings.

The application of a higher corrosion resistance coating modified with nano additions can effectively decrease or prevent corrosion from occurring. In the present work, a novel method is successfully developed for the modification of carbon steel surfaces aiming for high corrosion resistance using Sn—4% Zn alloy/nanoparticle composite (NiO+ Al2O3) coating. Sn—4% Zn alloy/nanoparticle composite (NiO+ Al2O3) coatings were deposed on carbon steel using a direct tinning process that involved a power mixture of Sn—4% Zn alloy along with a flux mixture. Regular coating and interface structures were achieved by individual Al2O3 and both NiO and Al2O3 nanoparticle combined additions in the Sn-Zn coating. The maximum coating thickness of 70 ± 1.8 µm was achieved for Al2O3 nanoparticles in the Sn-Zn coating. Interfacial intermetallic layer thickness decreased with all used nanoparticle additions in individual and hybrid conditions. The minimum intermetallic layer thickness of about 2.29 ± 0.28 µm was achieved for Al2O3 nanoparticles in the Sn—Zn coating. Polarization and impedance measurements were used to investigate the influence of the incorporated Al2O3, NiO, and hybrid Al2O3/NiO nanoparticles on the passivation of the low-carbon steel (LCS) corrosion and the coated Sn—Zn LCS in sodium chloride solution. It was found that the presence of Al2O3, NiO, and Al2O3/NiO nanoparticles remarkably improved the corrosion resistance. The corrosion measurements confirmed that the corrosion resistance of the coated Sn-Zn carbon steel was increased in the presence of these nanoparticles in the following order: Al2O3/NiO > NiO > Al2O3.