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Abstract: Ni/SiC nanocomposite coatings were obtained by electrochemical codeposition of SiC nanoparticles with nickel, from an additive-free Watts type bath. Pure Ni deposits were also produced under the same experimental conditions for comparison. The influences of the SiC nanoparticle concentration in the plating bath, the current density and the stirring rate on the composition of nanocomposite coatings were studied. It is shown that these parameters strongly affected the weight percentage of SiC nanoparticulates. The phase structures, the surface morphology, and the chemical composition of the coatings were characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS) respectively. The corrosion performance of the coatings was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The wear resistance and the microhardness of the coatings were studied also on a ball-on-disk tribometer and Vickers hardness tester, respectively. Characterization experiments showed that the SiC nanoparticle incorporation promoted changes in the texture of the nickel matrix. Moreover, the presence of SiC inhibits Ni growth, enhances re-nucleation, and hence results in a microcrystalline metal matrix. The results revealed that Ni/SiC nanocomposite coating provided excellent anti-corrosion performance and presented higher microhardness and better anti-wear performance compared to pure Ni coating. [Copyright &y& Elsevier]

The relation between time-dependent corrosion behaviors and microstructural characteristics of Sr modified and unmodified AlSi9 alloy was studied. The melted alloys were cast into the permanent mold at 700 °C casting temperature. The Effect of holding time in the furnace on chemical compositions of alloys was determined. Sr content of the modified alloys was 200 ± 5 ppm after 4 h and 50 ± 2 ppm after 17 h holding time. Microstructural properties were analyzed after casting. The corrosion behavior of AlSi9 depending on Sr content was investigated by means of electrochemical impedance spectroscopy technique and potentiodynamic polarization plots in 3.5 wt% NaCl solution at 25 °C. The effect of immersion time was examined at 1, 24, 72 and 120 h. The results indicated that high Sr content in AlSi9 alloy contributes to the formation of a finer eutectic phase and more stable corrosion behavior during immersion time. • The effect of Sr modification on the AlSi9 is investigated. • The relation between corrosion and microstructural characteristics are evaluated. • 50 ppm Sr is enough to obtain fine and fibrous eutectic morphology. • Sr Modification contributes to formation of stable and less defective oxide layer. • The protective effect of denser oxide/hydroxide layer is evident up to 120 h. [ABSTRACT FROM AUTHOR]

3XX series Al–Si alloys are generally used in corrosive environments open for oxidation such as rainwater and seawater. The dendrite size and characteristics of the eutectic Si are important factors determining the properties of A356 alloy. In this study, the microstructure of Sr modified A356 aluminum alloy and the changes in corrosion properties were investigated. The alloy was cast into die and sand molds to examine the effect of cooling parameters on the microstructure. Sr modification was carried out by adding four different weight percentages (0, 120, 170 and 250 ppm). Corrosion behavior of the produced alloys was investigated by two ways. One of them was electrochemical impedance spectroscopy technique and the other is potentiodynamic polarization plots that was carried out in 3.5 wt.% NaCl solution at 25 °C. The corrosion resistance of the alloy was found to be increasing as Sr content was increased which modified the morphology of the silicon in the alloy. [ABSTRACT FROM AUTHOR]