Method of preparing coating of biomedical magnesium alloys and magnesium or magnesium alloy comprising the coating

Abstract

A method including: employing pure magnesium or a magnesium alloy as a substrate material, and sanding and cleaning the substrate material; preparing an electrolyte including 0.8-8 mmol/L of Zn.sup.2+, 30-50 mmol/L of Ca.sup.+, 15-35 mmol/L of H.sub.2PO.sub.4.sup., 0-0.5 mol/L of NaNO.sub.3, and 0-0.05 mmol/L of a magnesium ion complexing agent; employing the substrate material as a cathode, a graphite flake as an anode, heating the electrolyte to a temperature of between 60 and 90 C., and synchronously immersing the cathode and the anode into the electrolyte; and implementing an electrochemical deposition method in the electrolyte for between 20 and 60 min.

Claims

1. A method, comprising: 1) employing pure magnesium or a magnesium alloy as a substrate material, and sanding and cleaning the substrate material; 2) preparing an electrolyte comprising 0.8-8 mmol/L of Zn.sup.2+, 30-50 mmol/L of Ca.sup.2+, 15-35 mmol/L of H.sub.2PO.sub.4.sup., 0-0.5 mol/L of NaNO.sub.3, and 0-0.05 mmol/L of a magnesium ion complexing agent; 3) employing the substrate material in 1) as a cathode, a graphite flake as an anode, heating the electrolyte to a temperature of between 60 and 90 C., and synchronously immersing the cathode and the anode into the electrolyte in 2), a distance between the cathode and the anode being between 3 and 5 cm; and 4) implementing an electrochemical deposition method in the electrolyte for between 20 and 60 min.

2. The method of claim 1, wherein the Zn.sup.2+ is selected from Zn(NO.sub.3).sub.2.6H.sub.2O, Zn(H.sub.2PO.sub.4).sub.2.2H.sub.2O, and a mixture thereof.

3. The method of claim 1, wherein the Ca.sup.2+ is selected from Ca(NO.sub.3).sub.2, Ca(NO.sub.3).sub.2.4H.sub.2O, and a mixture thereof.

4. The method of claim 1, wherein the H.sub.2PO.sub.4.sup. is selected from NH.sub.4H.sub.2PO.sub.4, NaH.sub.2PO.sub.4, and a mixture thereof.

5. The method of claim 1, wherein the magnesium ion complexing agent is ethylene diamine tetraacetic acid (EDTA) or a derivative thereof, salicylic acid or a derivative thereof, an amino acid, or a mixture thereof.

6. The method of claim 1, wherein the electrochemical deposition method is a constant potential cathodic deposition method, a galvanostatic deposition method, a unidirectional pulse electrodeposition method, or a bidirectional pulse electrodeposition method.

7. The method of claim 1, wherein the magnesium alloy is a magnesium-zinc alloy or a magnesium-aluminum alloy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a scanning electron microscope (SEM) image of a coating in Example 1 in the disclosure;

(2) FIG. 2A is an energy dispersive spectrometer (EDS) graph of a coating in Example 1 in the disclosure;

(3) FIG. 2B is a table showing the elemental composition of the coating in FIG. 2A;

(4) FIG. 3 is an X-ray diffraction (XRD) image of a coating in Example 1 in the disclosure; and

(5) FIG. 4 shows polarization curves of a substrate material before and after being coated in Example 1 in the disclosure.

DETAILED DESCRIPTION

(6) To further illustrate, experiments detailing a method of preparing a coating of biomedical magnesium alloys are described below. It should be noted that the following examples are intended to describe and not to limit the description.

Example 1

(7) A method of preparing a coating of biomedical magnesium and magnesium alloys for improving the corrosion resistance and biocompatibility of the biomedical magnesium and magnesium alloys is detailed as follows:

(8) 1) pretreatment of substrate material: a MgZnCa alloy was cut into 25 mm10 mm4 mm rectangular blocks as a substrate material. The substrate material was mechanically polished using 100#, 200#, 400#, 600# and 800# metallographic sandpapers in sequence, then placed in an anhydrous ethanol/acetone (the volume ratio was 1:1) mixed solution for ultrasonic cleaning (40 kHz) for 10 min, and then dried in the air;

(9) 2) preparation of electrolyte: Ca(NO.sub.3).sub.2.4H.sub.2O, Zn(NO.sub.3).sub.2.6H.sub.2O, NH.sub.4H.sub.2PO.sub.4 and NaNO.sub.3 were dissolved in water to yield an electrolyte, the electrolyte comprised: Ca(NO.sub.3).sub.2.4H.sub.2O, 40 mmol/L; Zn(NO.sub.3).sub.2.6H.sub.2O, 2 mmol/L; NH.sub.4H.sub.2PO.sub.4, 28 mmol/L; and NaNO.sub.3, 0.1 mol/L;

(10) 3) the substrate material in 1) was employed as a cathode, a graphite flake as an anode, the electrolyte was heated to 80 C., and the cathode and the anode were synchronously immersed into the electrolyte in 2), the distance between the cathode and the anode was 5 cm;

(11) 4) a bidirectional pulse electrodeposition method was implemented in the electrolyte; the pulse frequency was 10 Hz, positive peak current 10 mA/cm.sup.2, duty cycle 10%, reverse peak current 20 mA/cm.sup.2, duty cycle 4%, deposition time 40 min; and

(12) 5) a resulting product in 4) was collected, washed using deionized water, and dried in the air, to yield a coating of biomedical magnesium and magnesium alloys that features high corrosion resistance and biocompatibility.

(13) FIG. 1 shows a scanning electron microscope (SEM) image of the resulting coating; as can be shown, the coating crystals were massive and tightly arranged on the surface of the sample. FIGS. 2A and 2B show an energy dispersive spectrometer (EDS) graph and the elemental composition of the coating; as can be shown, there was no magnesium element in the coating, indicating that the substrate material was completely covered by the coating, and the coating has a certain thickness. The coating comprises zinc (Zn), calcium (Ca), and phosphorus (P), the mole ratio of Zn to Ca is about 2:1, and (Zn+Ca)/P is 1.28. FIG. 3 is an X-ray diffraction (XRD) image of the coating, indicating that the main component of the coating is CaZn.sub.2(PO.sub.4).sub.2.2H.sub.2O, and in combination with the EDS data, the mole ratio 1.28 of the (Zn+Ca)/P is obviously less than the mole ratio 1.5 in the chemical formula, which means the coating is a non-stoichiometric coating.

(14) The (Ca+Zn)/P mole ratio of the coating is non-stoichiometric. The non-stoichiometric coating can be degraded gradually with the time passing by in the physiological environment, which does not affect the degradation properties of the magnesium alloy as a biodegradable bone implant material, and the coating will gradually release Zn.sup.2+ during the degradation process; the Zn.sup.2+ can play a sustained active role in fracture healing.

(15) The corrosion resistance performance of the coating was tested in Kokubo's simulated body fluids (SBF) (refer to GB/T 24916-2009 standard). As shown in FIG. 4, the corrosion potential increases by 70 mV, the corrosion current density increases by two orders of magnitude, indicating that the coating can effectively reduce the corrosion rate of the substrate material.

Example 2

(16) A method of preparing a coating of biomedical magnesium and magnesium alloys for improving the corrosion resistance and biocompatibility of the biomedical magnesium and magnesium alloys is detailed as follows:

(17) 1) pretreatment of substrate material: a MgZnYNd alloy was cut into 25 mm10 mm4 mm rectangular blocks as a substrate material. The substrate material was mechanically polished using 100#, 200#, 400#, 600# and 800# metallographic sandpapers in sequence, then placed in an anhydrous ethanol/acetone (the volume ratio was 1:1) mixed solution for ultrasonic cleaning (40 kHz) for 10 min, and then dried in the air;

(18) 2) preparation of electrolyte: Ca(NO.sub.3).sub.2, Zn(H.sub.2PO.sub.4).sub.2.2H.sub.2O, NaH.sub.2PO.sub.4, NaNO.sub.3 and Na.sub.2EDTA were dissolved in water to yield an electrolyte, the electrolyte comprised: Ca(NO.sub.3).sub.2, 30 mmol/L; Zn(H.sub.2PO.sub.4).sub.2.2H.sub.2O, 0.8 mmol/L; NaH.sub.2PO.sub.4, 15 mmol/L; NaNO.sub.3, 0.1 mol/L; and Na.sub.2EDTA, 0.005 mol/L;

(19) 3) the substrate material in 1) was employed as a cathode, a graphite flake as an anode, the electrolyte was heated to 90 C., and the cathode and the anode were synchronously immersed into the electrolyte in 2), the distance between the cathode and the anode was 3 cm;

(20) 4) a unidirectional pulse electrodeposition method was implemented in the electrolyte; the pulse frequency was 10 Hz, peak current 10 mA/cm.sup.2, duty cycle 10%, and deposition time 30 min; and

(21) 5) a resulting product in 4) was collected, washed using deionized water, and dried in the air, to yield a coating of biomedical magnesium and magnesium alloys that features high corrosion resistance and biocompatibility.

Example 3

(22) A method of preparing a coating of biomedical magnesium and magnesium alloys for improving the corrosion resistance and biocompatibility of the biomedical magnesium and magnesium alloys is detailed as follows:

(23) 1) pretreatment of substrate material: a magnesium alloy AZ31 was cut into 25 mm10 mm4 mm rectangular blocks as a substrate material. The substrate material was mechanically polished using 100#, 200#, 400#, 600# and 800# metallographic sandpapers in sequence, then placed in an anhydrous ethanol/acetone (the volume ratio was 1:1) mixed solution for ultrasonic cleaning (40 kHz) for 10 min, and then dried in the air;

(24) 2) preparation of electrolyte: Ca(NO.sub.3).sub.2.4H.sub.2O, Zn(NO.sub.3).sub.2.6H.sub.2O, NH.sub.4H.sub.2PO.sub.4, NaNO.sub.3 and Cysteine were dissolved in water to yield an electrolyte, the electrolyte comprised: Ca(NO.sub.3).sub.2.4H.sub.2O, 50 mmol/L; Zn(NO.sub.3).sub.2.6H.sub.2O, 8 mmol/L; NH.sub.4H.sub.2PO.sub.4, 27 mmol/L; NaNO.sub.3, 0.1 mol/L; and Cysteine, 0.05 mol/L;

(25) 3) the substrate material in 1) was employed as a cathode, a graphite flake as an anode, the electrolyte was heated to 70 C., and the cathode and the anode were synchronously immersed into the electrolyte in 2), the distance between the cathode and the anode was 4 cm;

(26) 4) a galvanostatic deposition method was implemented in the electrolyte; the current density was 0.5 mA/cm.sup.2, and deposition time 60 min; and

(27) 5) a resulting product in 4) was collected, washed using deionized water, and dried in the air, to yield a coating of biomedical magnesium and magnesium alloys that features high corrosion resistance and biocompatibility.

Example 4

(28) A method of preparing a coating of biomedical magnesium and magnesium alloys for improving the corrosion resistance and biocompatibility of the biomedical magnesium and magnesium alloys is detailed as follows:

(29) 1) pretreatment of substrate material: a pure magnesium was cut into 25 mm10 mm4 mm rectangular blocks as a substrate material. The substrate material was mechanically polished using 100#, 200#, 400#, 600# and 800# metallographic sandpapers in sequence, then placed in an anhydrous ethanol/acetone (the volume ratio was 1:1) mixed solution for ultrasonic cleaning (40 kHz) for 10 min, and then dried in the air;

(30) 2) preparation of electrolyte: Ca(NO.sub.3).sub.2.4H.sub.2O, Zn(NO.sub.3).sub.2.6H.sub.2O, NH.sub.4H.sub.2PO.sub.4, NaNO.sub.3 and salicylic acid were dissolved in water to yield an electrolyte, the electrolyte comprised: Ca(NO.sub.3).sub.2.4H.sub.2O, 34 mmol/L; Zn(NO.sub.3).sub.2.6H.sub.2O, 1 mmol/L; NH.sub.4H.sub.2PO.sub.4, 35 mmol/L; NaNO.sub.3, 0.1 mol/L; and salicylic acid, 0.01 mol/L;

(31) 3) the substrate material in 1) was employed as a cathode, a graphite flake as an anode, the electrolyte was heated to 60 C., and the cathode and the anode were synchronously immersed into the electrolyte in 2), the distance between the cathode and the anode was 4.5 cm;

(32) 4) a galvanostatic deposition method was implemented in the electrolyte; the voltage was 3 V, and deposition time 45 min; and

(33) 5) a resulting product in 4) was collected, washed using deionized water, and dried in the air, to yield a coating of biomedical magnesium and magnesium alloys that features high corrosion resistance and biocompatibility.

(34) Unless otherwise indicated, the numerical ranges involved include the beginning and end values. It will be obvious to those skilled in the art that changes and modifications may be made, and therefore, the aim in the appended claims is to cover all such changes and modifications.