Now showing 1 - 2 of 2
  • Publication
    Corrosion behaviour of powder metallurgy aluminium matrix composite reinforced with alumina Saffilâ„¢ short fibre
    (Universiti Malaysia Perlis (UniMAP), 2010-09-06) ;
    Normah Che Man
    The corrosion behaviour of PM Al composite will be affected by the presence of alloying element and reinforcing phase in the composite. This study focused on magnesium and alumina Saffil™ short fibres reinforcement affected to corrosion behaviour of PM AMCs in 3.5wt% NaCl. PM Al composite and PM Al-Mg composite were fabricated from flaky aluminium powder, 2wt% granular magnesium and 15wt% alumina Saffil™ short fibres. The corrosion testing was done using potentiostat Gamry G300 to create Tafel plot and polarization curve. The corrosion effects were analyse using scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). From experiment, pitting was localized surrounding the magnesium constituents which occur randomly throughout the surface of PM Al-Mg composite. XRD analysis revealed that aluminum oxide (δ-Al Al1.67O4), aluminium hydroxide (Al (OH)3) and aluminium oxide (α-Al2O3) phases were detected in oxide film. The corrosion current density (Icrit) of PM Al composite is lower than PM Al-Mg composite which is 2.0 x 10-1 A/cm2 and 4.0 x10-1 A/cm2, respectively. Magnesium is used as inhibitor in corrosion behaviour of PM Al-Mg composite have been changed and protected with a stable formation of oxide film. The corrosion resistance of PM Al-composite was decreased with the presence of alumina Saffil™ short fibres in composite due to discontinuities in oxide film provided the corrosion initiated in sample.
  • Publication
    Fabrication of calcium phosphate coating on pure magnesium substrate via simple chemical conversion coating: surface properties and corrosion performance evaluations
    The main objective of the current work was to fabricate calcium phosphate (CaP) coating on 99.9% purity magnesium, Mg substrate through simple chemical conversion method and evaluated the surface properties and corrosion performance of the coated substrates. The chemical conversion method was done by immersing the samples inside primary phosphating bath and followed by secondary treatment in alkaline solutions. The coated samples from the primary (PRI) and secondary (SEC) coating treatment were analyzed from morphological, topographical, and phase analysis aspects. The corrosion behaviour of the coatings inside simulated body fluid was assessed by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The PRI and SEC coated were composed of dicalcium phosphate dehydrate (DCPD) and hydroxyapatite (HA), respectively. Both of the coatings improved the corrosion resistance of the Mg substrate. The corrosion potentials, Ecorr of the coated samples becomes nobler compared to the bare substrates. EIS shows that the polarization resistance, Rp is improved about 40 and 2 times fold for PRI and SEC compared to the uncoated samples. Furthermore, PRI shows better corrosion resistance compared to SEC due to lower porosity along with thicker and better coating coverage.
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