Papers by Author: Jia Cheng Gao

Abstract: In this paper, self-assembled monolayers (SAMs) of stearic acid (SA) surface treatment on pure magnesium were studied to improve bioactivity and corrosion resistance of pure Mg. Three pre-treatment methods (HCl-NaOH treatment, alkali-heat treatment and heat treatment) were used. SAMs treated samples were soaked in simulated body fluid (SBF) and untreated samples were taken as control. The pH variation of SBF solution was examined everyday. The electrochemical property of treated and untreated samples was tested to evaluate the anticorrosion performance of organic surface layer. Scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) analysis were performed to observe the surface appearance and to identify the composition and phases of samples. The results showed that stearic acid SAMs had successfully been assembled on the surface of the samples, which had a good effect on corrosion resistance of materials and decreased the electric current density of SAM-sample 1% to that untreated sample; SAM inhibited the form of Mg(OH)₂ and had a good influence on bioactivities of pure magnesium.

Abstract: In order to improve the corrosion resistance of Mg alloys in applications as degradable implant material. Fluoride conversion coating was synthesized on Mg alloy AZ31 by immersion in hydrofluoric acid (HF) with various concentrations. The effect of hydrofluoric acid (HF) treatment on the corrosion behavior of the Mg alloy AZ31 was investigated by potentiodynamic electrochemical technique and immersion tests. The XRD analysis indicated the fluoride conversion coating was amorphous, with smooth and compact surface. Electrochemical and immersion tests proved that the fluoride conversion coatings significantly improved the corrosion resistance of AZ31. The most improved corrosion protection was achieved using the concentrations of 40 % and 72 h of treatment time, resulting in corrosion rates 20 times lower than those of untreated samples, showing that fluoride coating by conversion treatment is a simple and promising way of enhancing the corrosion resistance of Mg in Hanks' solution.