Microstructure, Mechanical Properties and Corrosion Behaviors of Al–Li–Cu–Mg–Ag–Zn Alloys

Combined with microstructure characterization and properties tests, the effects of Zn contents on the mechanical properties, corrosion behaviors, and microstructural evolution of extruded Al–Li–Cu–Mg–Ag alloys were investigated. The results show that the increase in Zn contents can accelerate hardening kinetics and improve the hardness of peak-aged alloys. The Zn-added alloys present non-recrystallization characteristics combined with partially small recrystallized grains along the grain boundaries, while the T1 phase with finer dimension and higher number density could explain the constantly increasing tensile strength. In addition, increasing Zn contents led to a lower corrosion current density and a shallower maximum intergranular corrosion depth, thus improving the corrosion resistance of the alloys. Zn addition, distributed in the central layer of T1 phases, not only facilitates the precipitation of more T1 phases but also reduces the corrosion potential difference between the T1 phase and the matrix. Therefore, adding 0.57 wt.% Zn to the alloy has an excellent combination of tensile strength and corrosion resistance. The properties induced by Zn under the T8 temper (solid solution treatment + water quenching + 5% pre-strain+ isothermal aging), however, are not as apparent as the T6 temper (solid solution treatment + water quenching + isothermal aging).

Effect of Minor Alloying Elements (C, Ni, Cr, Mo) on the Long-Term Corrosion Behaviors of Ultrahigh-Strength Automotive Steel Sheet in Neutral Aqueous Environment

This study examined the effects of minor alloying elements (C, Ni, Cr, and Mo) on the long-term corrosion behaviors of ultrahigh-strength automotive steel sheets with a tensile strength of more than 1800 MPa. A range of experimental and analytical results showed that the addition of Ni, Cr, and Mo decreased the corrosion current density and weight loss in electrochemical and immersion tests, respectively, in a neutral aqueous condition. This suggests that the minor addition of elements to steel can result in improved corrosion resistance even for long-term immersion periods. This is closely associated with the formation of thin and stable corrosion scale on the surface, which was enriched with the alloying elements (Ni, Cr, and Mo). On the other hand, their beneficial effects did not persist during the prolonged immersion periods in steel with a higher C content, suggesting that the beneficial effects of the minor addition of Ni, Cr, and Mo were overridden by the detrimental effects of a higher C content as the immersion time was increased. Based on these results, lower C and the optimal use of Ni, Cr, and Mo are suggested as a desirable alloy design strategy for developing ultrahigh-strength steel sheets that can be exposed frequently to a neutral aqueous environment.

Effect of Galvanic Corrosion on the Degradability of Biomedical Magnesium

With recent progress in clinical trials and scale-up applications of biodegradable magnesium-based implants, the scenarios of transplanting biodegradable Mg with other non-degradable metals may occur inevitably. Galvanic corrosion appears between two metallic implants with different electrochemical potentials and leads to accelerated degradation. However, a quantitative measurement on the galvanic corrosion of Mg in contact with other metallic implants has not been conducted. Here we study the corrosion behaviors and mechanical attenuation of high purity magnesium (Mg)in contact with stainless steel (316L), pure titanium (TA2), and magnesium alloy (AZ91) respectively to form different galvanic couples in simulated body fluids. The results show that all of these three heterogeneous metal pairs accelerate the degradation of high purity Mg to different degrees, yielding declined tensile strength and mechanical failure after 4 days of immersion. Our observations alert the potential risk of co-implanting different metallic devices in clinical trials.

Corrosion Behaviors of SS310 and IN718 Alloys in Molten Carbonate

Long-lasting metallic materials are key to enabling a robust and reliable molten carbonate electrolyzer. In this paper, the corrosion behaviors of SS310 and IN718 in molten Li2CO3-K2CO3-Na2CO3 under CO2-O2 atmosphere were systematically studied. The results show that IN718 had a lower corrosion rate than that of SS310 because of the higher Ni concentration. In addition, increasing the temperature and decreasing the oxygen concentration can reduce the corrosion rate of both SS310 and IN718. As a result, IN718 is a suitable material to be used in molten salt electrolyzers. Overall, engineering the alloy and molten salt compositions as well as manipulating the gas atmosphere can suppress the corrosion of metallic materials, thereby screening durable metallic materials for high-temperature molten carbonate electrolyzers.

Roughness Effect on Corrosion of Gr-Cu -Ni Coated Steel in Saline Water

Effect of surface roughness on corrosion behavior for carbon steel was coated by metallic layers Cu- Ni Reinforced with Gr layers. Surface finishing P320, P600 and P1200 mesh used until a mirror shiny surface before metallic coated with Gr layers at consecrations 0.25, 0.5, 1and 2 g/l of Gr. First, X-ray diffraction), electron microscopy associated for carbon steel & Gr and Microscopic test for coated specimens. The techniques were performed to study the effect of saline water (3.5%) on the corrosion behaviors, Open circuit potential, Tafel polarization and impedance spectroscopy tests. At P320 Equivalent Circuit elements were decreasing but, Corrosion reaction’s Rp was increased at 5 min and 0.25 g/l. And also, coating’s Rpore with Electrolyte’s Ru were increasing at 30 min for 0.5 g/l, and also coating’s Rpore and Electrolyte’s Ru were increased at 20 min for 1 g/l, At P600 ECE’s were decreasing but, corrosion reaction’s Rp was increased at 30 min 1 g/l, and also, coating’s Rpore and Electrolyte’s Ru were increased at 20 min for 1 g/l, and At P1200 ECE’s were decreasing but, Coating’s Ccoat was increased at 5 min 0.25 g/l, and also coating’s Rpore and Electrolyte’s Ru were increased at 0.5g/l, 30 min.

Reactivity and Corrosion Behaviors of Ti6Al4V Alloy Implant Biomaterial under Metabolic Perturbation Conditions in Physiological Solutions

The corrosion of implant biomaterials is a well-known critical issue when they are in contact with biological fluids. Therefore, the reactivity of Ti6Al4V implant biomaterials is monitored during immersion in a Hanks’ physiological solution without and with added metabolic compounds, such as lactic acid, hydrogen peroxide, and a mixture of the two. Electrochemical characterization is done by measuring the open circuit potential and electrochemical impedance spectroscopy performed at different intervals of time. Electrochemical results were completed by morphological and compositional analyses as well as X-ray diffraction before and after immersion in these solutions. The results indicate a strong effect from the inflammatory product and the synergistic effect of the metabolic lactic acid and hydrogen peroxide inflammatory compound on the reactivity and corrosion resistance of an implant titanium alloy.