Study Of Ca-P Mineralized Layer Induced Deposit On Magnesium Alloy Surface In Simulated Body Fluid

Magnesium alloy is a light weight metal with mechanical properties similar to natural bone, moreover magnesium ion play an important role in biological systems of human, The biocompatible, osteoconductive of magnesium alloy are rather good, magnesium alloy have the potential to serve as degradable implants for loadbearing applications. But the corrosion resistance of magnesium alloy is poor, it limits the using of magnesium alloy as implant material for load-bearing. To improve the corrosion resistance, many researchers focus their eyes on surface treatment technology.Hydroxyapatite is an important apatite, and also is the important inorganic composition of nature bone. Its bioactivity and biocompatibility are excellent. The mechanical property of hydroxylapatite is poor and can not be used as implant materials for load-bearing alone. Biomimetic method is a newly developing method, we can deposit apatite coatings on many matrix through this method.Study of nature mineralization show some special groups with negative charge can absorb Ca2+ and then induced apatite deposit。Phytic acid contains—H2PO4, EDTA contains—COOH, they are all very good metal-chelator. They have stable and fine chelating ability in large pH range to chelating divalent metal cations, especially to Ca2+ and Mg2+.So phytic acid and EDTA be can used to dispose the magnesium alloy samples, then SAMs will be formation. The SAMs contains—H2PO4 or—COOH, can absorb Ca2+ and induce apatite nucleation.This paper synthesizes the method of SAMs and biomimetic to dispose apatite coating on magnesium alloy samples surface. First using phytic acid or EDTA to prepare SAMs, and then pre-calcified the matrix through dropping KH2PO4 to CaCl2, at last soaking the samples in biomimetic solution. This paper also studys the affection of citric acid on deposition of apatite when different mass citric acid was dissolved in biomimetic solution.By analysis the mass loss of samples and the pH of the soaking solution, the conclution can be got that both phytic acid SAMs and EDTA SAMs have the function of protecting the samples and induce the deposit of apatite, phytic acid SAMs is better. The result of SEM, XRD and FTIR indicate that a uniform and rather dense apatite mineralized layer which the main phase is hydroxyapatite has been deposition on samples surface that treated by phytic acid after soaking 12 days in biomimetic solution. After soaking 8 days, a uniform and dense apatite mineralized layer formed on samples surface treated by EDTA, hydroxyapatite is also the main phase of this layer. Both their morphology are petals, But the difference of them are apparently. The microstructure of mineralized layer that induced by EDTA SAMs is more clear and regular.The result of experiment show that citric acid not only can impact the deposition of apatite but also can impact the corrosion rate of samples.