Magnesium alloys are a unique choicefor orthopedic implants due to their Biocompatibility and Biodegradability properties. In this article, the impact of hot-extrusion process is investigated on microhardness, microstructure, and corrosion behavior of magnesium/2. 5wt% hydroxyapatite (HA) rods as a Bio-composite. Hot extrusion process was implemented on the as-cast samples in two different steps resulting two various total extrusion ratios of 5: 1 and 20: 1. The corrosion susceptibility of the extruded composites was studied by polarization test in simulated body fluid (SBF) as a corrosive environment. According to the results, adding hydroxyapatite reinforcing particles and applying higher extrusion ratios caused grain refinement in the matrix comparing to the pure magnesium. Moreover, while the hardness of the pure magnesium sample decreased slightly after the second extrusion pass, it was enhanced in the composite specimens. Besides, both extrusion ratio and reinforcing particles had direct effects on the corrosion behavior, so that with the presence of HA particles and applying the higher extrusion ratio, the corrosion resistance of the samples was improved.

TiO2 nanoparticle coatings have beneficial antifungal and anti-bacterial properties, which make them a reliable alternatives to resist against the occurrence and growth of viral, bacterial, parasitic or fungal infections. In this article, we have successfully produced a unique TiO2 coating on mild steel substrate by using sol-gel deposition technique to improve its corrosion resistance and anti-fungal properties. The coating was deposited on a mild steel substrate by a dip coating technique followed by three different type of cooling rates: 1, 3 and 6 ˚C/min. The phase morphology, micro-structure and composition of the coatings were studied by X-ray diffraction and field emission scanning electron microscopy characterization techniques. Bio-corrosion behaviour was evaluated by conducting electrochemical impedance spectroscopy and potentiodynamic polarization tests in 0.9 wt % NaCl solution at 37 ˚C to simulate aggressive environment. The antifungal performances of the coating have been studied on Aspergillus nigger and Aspergillus flavus. The specimens Reduction of corrosion current intensity for coated specimens varies from 15.8 to 0.8 µA/〖cm〗^2and shifting open circuit potential (Eocp) from -1550 mV to -391 mV, for heating and cooling rate 6 and 1 ˚C/min, respectively. Shifting Eocp towards more positive values by decreasing heating and cooling rate of heat treatment, enhanced corrosion resistance by reducing porosities and cracks in the coating. It is worthy to note that the antifungal properties TiO2 nanostructured coating on Aspergillus nigger and Aspergillus flavus are 50 and 30 % after 2 months, respectively.

The effect of ultrasonic impact treatment (UIT) was studied on the microstructure and corrosion behavior of Haynes 25 superalloy. The UIT was performed at a frequency of 20 kHz, tool feeding rates of 0.08, 0.12, and 0.16 mm/rev, vibration amplitudes of 10, 28, and 50% of the machine power, static pressures of 0.1 and 0.9 bar at the different number of passes (one, two, three, five, and seven). According to the results, the UIT severely deformed the surface layers up to a depth of about 100 μm and promoted the emergence of deformation bands/strain-induced martensite (-phase) up to a depth of about 400 μm. The UIT also produced ultrafine grain structure in the surface region and due to the deformation inhomogeneity developed surface compressive residual stresses. The Tafel polarization tests indicated that applying one pass UIT at the static pressures of 0.1 and 0.9 bar reduced the corrosion current (from 4.16 A/cm2 to 1.3 A/cm2 and 2.18 A/cm2, respectively), and the corrosion potential (from -0.6 V to -0.7 V and -0.8 V, respectively). This behavior was found to be due to promotion of surface oxidation and formation of protective layer on the surface. Despite increasing the surface smoothness, further increasing the UIT pass number to seven, probably due to encouraging the formation of surface pits/microcracks increased the corrosion current and corrosion rate by about 45%. According to the electrochemical impedance tests, at the static pressure of 0.9 bar, the as-received and seven-pass UITed samples showed the lowest corrosion resistance whilst one-pass and two-pass UITed samples revealed the highest corrosion resistance. The effect of tool feeding rate on the corrosion resistance was found to be minor.

The corrosion protection of aluminum flake pigments has been extended by means of an encapsulating inorganic/organic silica/polystyrene hybrid nanolayer. A silica nanolayer encapsulated the surface of aluminum flakes (Al) by hydrolysis and polycondensation of tetraethylorthosilicate via sol–gel process to yield Al/Si flakes. Then, 3-methacryloxypropyltrimethoxysilane (MPS) was used as surface modifier which has polymerizable groups to participate in polymerization reaction (Al/Si/MPS). A polystyrene (PS) coating layer was applied on Al/Si/MPS flakes by free radical polymerization of styrene initiating with Azobisisobutyronitrile at 60 °C and subsequent washing of free chains with solvent yielded Al/Si/PS flakes. Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and scanning electron microscopy showed that silica and PS nanolayers were formed on the aluminum flakes. The attached PS chains on the surface were detached by hydrofluoric acid aqueous solution and analyzed by gel permeation chromatography (GPC). Also, a transmission electron microscopy image showed clearly that the encapsulating layers are in the scale of nano. Good results were obtained in terms of corrosion protection in acidic and alkaline solutions, indicating that the silica/polymer hybrid nanolayer coating acts as an efficient protective film. After encapsulating the flakes, the evolved hydrogen volume was dropped and hybrid nanolayer resulted in no evolved hydrogen volume.