| Magnesium and magnesium alloys were limited in the clinical application asbiodegradable bone fixation materials because they were degraded quickly. A new methodnamed pure magnesium ultrasound micro-arc oxidation(UMAO) dipping composite treatmentwas put forward that process different composite treatments included HF-Na2SiO3, HF-silica sol(CSG) and NaOH-silane coupling agent (SCA) after UMAO treating on pure magnesium insilicate electrolyte to regulate the rate of degradation and bioactivity of pure magnesium UMAObiological coating,Search Engine Marketing(SEM), Energy Dispersive Spectrometry(EDAX), X-raydiffraction (XRD), the contact angle tester, the scratch tester, the electrochemical workstationand the pin-disc friction and wear tester were investigated to analyze the microstructure, phasecomposition, the phase structure, the contact angle, adhesion force, electrochemical corrosionand friction coefficient of the UMAO-composite coatings on pure magnesium. The technologyand the treatment mechanism of different UMAO-composite coating were discussed. Theformation of the bone-like apatite on coatings were analyzed after immersed in simulated bodyfluid.The surface pores of the dense biological coating on pure magnesium were filled bycomposite after UMAO-composite treatment. The phase structure of UMAO coating wasMgO, MgSiO3,SiO2and MgF2. The adhesion force of single UMAO coating was4.6Nwhile that increaseed to4.8N-7.8N after combined treatment. The friction coefficient ofsingle UMAO coating was1.1while that reduced to0.8-0.35after composite treatment.The MAO-HF-CSG coating had the best adhesion force and wear resistance whoseadhesion force reached to7.8N and friction coefficient reduced to0.35. The corrosionresistance of the different treatment coatings was superior to single UMAO coating. Thecorrosion resistance of UMAO-NaOH (3mol/L)-SCA coating was the best whose corrosionpotential (Ecorr) improved75mV and the corrosion current density (Icorr) lowed two ordersof magnitude relative to single UMAO coating. The MgO of coating converts to Mg(OH)2after immersed in SBF. The corrosion products containing Ca, P and other elementsgenerated some bone-like apatite. The pores of the bio-coatings on pure magnesium prepared by UMAO-compositeprocesses were filled by the particles generated after chemical reaction and physical changes.The corrosion resistance of the composite coatings were improved because the coatingprevented the corrosive media invading into the substrate. The degradation of thecomposite coating can be controlled. In the main, the UMAO-NaOH (3mol/L)-SCAcoating had the best mechanical properties and corrosion resistance. |
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