A method for preparing a magnesium alloy surface hydroxyapatite coating

Abstract

The application provides a preparation method of a magnesium alloy surface hydroxyapatite coating and relates to the field of medical magnesium alloy corrosion protection. The method comprises the following steps: (1) soaking the magnesium alloy in a phosphoric acid solution to prepare a phosphorite coating; (2) placing the component treated in step (1) in a phosphate solution to prepare a struvite-like coating; and (3) placing the component treated in step (2) in a dihydrogen phosphate solution to prepare a hydroxyapatite coating. The application has universality for magnesium alloys of different types and shapes, does not need to pretreat the magnesium alloy, does not need complicated operation equipment, and is lower in cost. The prepared hydroxyapatite coating is firmly combined with the substrate, the coating has no cracks, and the protection effect is excellent. The steps are closely related, no intermediate rinsing and treatment are needed, the process is simple, the coating performance is ensured, and the energy saving and environmental protection requirements are considered.

Description

Technical Field

[0001] This invention relates to the field of corrosion protection for medical magnesium alloys, and in particular provides a method for preparing a hydroxyapatite coating on the surface of a magnesium alloy. Background Technology

[0002] Magnesium alloys possess advantages that traditional orthopedic materials such as 316L stainless steel, titanium alloys, and Co-Cr-Ni alloys cannot match. Their density and elastic modulus are closest to natural bone, reducing or eliminating the stress-shielding effect during bone tissue repair. Secondly, they can be readily degraded and absorbed within bone, perfectly addressing the risks of permanent implantation associated with traditional orthopedic materials, avoiding the need for secondary surgery, and significantly reducing patient pain, psychological stress, and financial costs. However, magnesium alloys are prone to rapid dissolution within bone, causing inflammation of the surrounding tissues and leading to premature failure. Therefore, to prevent rapid degradation and enhance biocompatibility, a hydroxyapatite coating is typically applied to the surface of magnesium alloys.

[0003] Existing hydroxyapatite coatings on magnesium alloy surfaces are prepared by methods such as ion co-deposition, electrodeposition, sol-gel method, and spraying. However, all existing preparation methods have various drawbacks: for example, hydroxyapatite coatings prepared by ion co-deposition and electrodeposition have poor adhesion and are easily peeled off from the substrate, resulting in reduced corrosion resistance; the sol-gel method has difficulty controlling the uniformity of coating thickness, and the evaporation of solvent and residual moisture can easily lead to coating cracking; the spraying method is difficult to use on irregularly shaped magnesium alloys, and the density of the coating is greatly affected by temperature. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a hydroxyapatite coating on a magnesium alloy surface. This method is applicable to various types of magnesium alloys, is simple to operate, can be completed at room temperature, and requires no pretreatment of the magnesium alloy, thus resulting in low cost. Furthermore, this method prepares hydroxyapatite through chemical conversion, ensuring the adhesion between the coating and the substrate and significantly improving the corrosion resistance of the magnesium alloy.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a hydroxyapatite coating on a magnesium alloy surface, the specific steps of which are as follows: (1) Magnesium alloy was immersed in phosphoric acid solution to prepare a magnesium phosphate coating; (2) The components treated in step (1) are placed in a phosphate solution for treatment to prepare a guano-like coating; (3) The components treated in step (2) are placed in a dihydrogen phosphate solution to prepare a hydroxyapatite coating.

[0006] Further: The composition and mass percentage of the phosphoric acid solution in step (1) are as follows: phosphoric acid: 60-80%, surfactant: 0.01-0.1%, corrosion inhibitor: 0.01-0.05%, the remainder being H2O; the treatment time is 30 min to 2 h.

[0007] Further: The composition and mass percentage of the phosphate solution in step (2) are as follows: phosphate: 60-80%, sodium hydroxide: 0.05%~0.1%, the remainder is H2O; the treatment time is 6~12 h; the pH of the phosphate solution is 9-12.

[0008] Further: The composition and mass percentage of the dihydrogen phosphate solution in step (3) are as follows: dihydrogen phosphate: 50-70%, calcium salt: 10-20%, the remainder is H2O; the treatment time is 12-24 h.

[0009] Further: The surfactant is one or more of sodium dodecylbenzenesulfonate, fatty acid glycerides, and polysorbates.

[0010] Further: The corrosion inhibitor is one or more of hexamethylenetetramine, phosphorus-containing dimethylthiourea, and aldehyde-amine condensate.

[0011] Further: The phosphate is one or more of dipotassium hydrogen phosphate, disodium hydrogen phosphate, and diammonium hydrogen phosphate.

[0012] Further: The dihydrogen phosphate salt mentioned is one or more of potassium dihydrogen phosphate, sodium dihydrogen phosphate, and ammonium dihydrogen phosphate.

[0013] Further: The calcium salt is one or more of EDTA-Ca, Ca(NO3)2, and CaCl2.

[0014] Struvite is a mineral whose structure is similar to that of struvite.

[0015] Beneficial effects of this invention: (1) This invention is universally applicable to magnesium alloys of different types and shapes. It does not require pretreatment of magnesium alloys or complex operating equipment, and is therefore more cost-effective.

[0016] (2) The hydroxyapatite coating prepared by the present invention is firmly bonded to the substrate, has no cracks, and provides excellent protection.

[0017] (3) This invention employs a chemical conversion method to prepare a hydroxyapatite coating on the surface of a magnesium alloy. First, the magnesium alloy is treated with a phosphoric acid solution to prepare a magnesium phosphate coating. Then, a struvite-like coating is prepared by replacing the hydrogen (H) in the magnesium phosphate with alkali metal elements. Finally, a hydroxyapatite coating is prepared by replacing the Mg in the struvite with Ca, and the -OH group can replace the alkali metal elements. The steps are closely related, requiring no intermediate rinsing or treatment, resulting in a simple process that ensures coating performance while also meeting energy-saving and environmental protection requirements. Detailed Implementation

[0018] The present invention will be further described below with reference to embodiments, but is not limited thereto.

[0019] Example 1 (1) Preparation of magnesium phosphate coating on magnesium alloy surface. The solution composition and mass percentage are as follows: 60% phosphoric acid, 0.1% sodium dodecylbenzenesulfonate, 0.05% hexamethylenetetramine, and the remainder is water; the treatment time is 30 min.

[0020] (2) A struvite-like coating was prepared on the magnesium alloy surface coated with phosphatic magnesium oxide. The solution composition and mass percentages used were as follows: 60% K2HPO4, 0.05% sodium hydroxide, and the remainder was water; pH was adjusted to 9 and the treatment time was 6 h.

[0021] (3) A hydroxyapatite coating was prepared on the surface of a magnesium alloy coated with struvite. The solution composition and mass percentages used were as follows: 60% KH2PO4, 10% EDTA-Ca, and the remainder was water; the treatment time was 12 h.

[0022] Example 2 (1) Preparation of magnesium phosphate coating on magnesium alloy surface. The solution composition and mass percentage are as follows: 70% phosphoric acid, 0.1% fatty acid glycerides, 0.05% phosphoric acid-containing dimethyl thiourea, and the remainder is water; the treatment time is 1 h.

[0023] (2) A struvite-like coating was prepared on the magnesium alloy surface coated with phosphatic magnesium oxide. The solution composition and mass percentages used were as follows: 70% K2HPO4, 0.05% sodium hydroxide, and the remainder was water; pH was adjusted to 10 and the treatment time was 12 h.

[0024] (3) A hydroxyapatite coating was prepared on the surface of a magnesium alloy coated with struvite. The solution composition and mass percentages used were as follows: 60% KH2PO4, 10% CaCl2, and the remainder was water; the treatment time was 10.5 h.

[0025] Example 3 (1) Preparation of magnesium phosphate coating on magnesium alloy surface. The solution composition and mass percentage are as follows: 80% phosphoric acid, 0.1% fatty acid glycerides, 0.05% phosphoric acid-containing dimethyl thiourea, and the remainder is water; the treatment time is 2 h.

[0026] (2) A struvite-like coating was prepared on the surface of a magnesium alloy coated with phosphogypsum. The solution composition and mass percentages used were as follows: 65% K2HPO4, 0.05% sodium hydroxide, and the remainder was water; pH was adjusted to 10 and the treatment time was 10 h.

[0027] (3) A hydroxyapatite coating was prepared on the surface of a magnesium alloy coated with struvite. The solution composition and mass percentages used were as follows: 60% NaH2PO4, 10% CaCl2, and the treatment time was 15 h.

[0028] Example 4 (1) Preparation of magnesium phosphate coating on magnesium alloy surface. The solution composition and mass percentage are as follows: 80% phosphoric acid, 0.1% fatty acid glycerides, 0.05% polysorbate, and the remainder is water; the treatment time is 1 h.

[0029] (2) A struvite-like coating was prepared on the surface of a magnesium alloy coated with phosphogypsum. The solution composition and mass percentages used were as follows: 60% (NH4)2HPO4, 0.05% sodium hydroxide, and the remainder was water; pH was adjusted to 9 and the treatment time was 12 h.

[0030] (3) A hydroxyapatite coating was prepared on the surface of a magnesium alloy coated with struvite. The solution composition and mass percentages used were as follows: 60% NaH2PO4, 10% CaNO3, and the treatment time was 24 h.

[0031] Example 5 (1) Preparation of magnesium phosphate coating on magnesium alloy surface. The solution composition and mass percentage are as follows: 70% phosphoric acid, 0.1% fatty acid glycerides, 0.05% polysorbate, and the remainder is water; the treatment time is 1.5 h.

[0032] (2) A struvite-like coating was prepared on the surface of a magnesium alloy coated with phosphogypsum. The solution composition and mass percentages used were as follows: 75% (NH4)2HPO4, 0.05% sodium hydroxide, and the remainder was water; pH was adjusted to 10 and the treatment time was 6 h.

[0033] (3) A hydroxyapatite coating was prepared on the surface of a magnesium alloy coated with struvite. The solution composition and mass percentage were as follows: 60% NH2H2PO4, 10% EDTA-Ca, and the treatment time was 12 h.

[0034] The above Examples 1-5 were tested using a WS-2005 scratch testing machine according to the mechanical industry standard JB / T8554-1997 recognized by the Ministry of Machinery Industry of the People's Republic of China. The results showed that the coating adhesion was 178 N, indicating good adhesion.

[0035] Comparative Example 1 The parameters for electrodeposition preparation of hydroxyapatite are as follows. The solution composition and mass percentages are as follows: 2% M Ca(NO3)2, 1% M (NH4)2HPO4, and the remainder is water; DC voltage of 2.5 V and deposition time of 30 min.

[0036] Scratch tests showed that the adhesion of the electrodeposited coating was 105 N, which is poor.

[0037] Matters not covered in this invention are common knowledge.

[0038] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a hydroxyapatite coating on a magnesium alloy surface, characterized in that: The specific steps of this method are as follows: (1) Magnesium alloy was immersed in phosphoric acid solution to prepare a magnesium phosphate coating; (2) The components treated in step (1) are placed in a phosphate solution for treatment to prepare a guano-like coating; (3) The components treated in step (2) are placed in a dihydrogen phosphate solution to prepare a hydroxyapatite coating; The composition and mass percentage of the phosphoric acid solution in step (1) are as follows: phosphoric acid: 60-80%, surfactant: 0.01-0.1%, corrosion inhibitor: 0.01-0.05%, and the remainder is H2O; the treatment time is 30 min to 2 h. The composition and mass percentage of the phosphate solution in step (2) are as follows: phosphate: 60-80%, sodium hydroxide: 0.05%~0.1%, the remainder being H2O; treatment time: 6~12 h; pH of phosphate solution: 9-12; The composition and mass percentage of the dihydrogen phosphate solution in step (3) are as follows: dihydrogen phosphate: 50-70%, calcium salt: 10-20%, the remainder being H2O; the treatment time is 12-24 h; the phosphate is one or more of dipotassium hydrogen phosphate, disodium hydrogen phosphate, and diammonium hydrogen phosphate; the dihydrogen phosphate is one or more of potassium dihydrogen phosphate, sodium dihydrogen phosphate, and diammonium dihydrogen phosphate; the calcium salt is one or more of EDTA-Ca, Ca(NO3)2, and CaCl2; the above method can be completed at room temperature.

2. The method for preparing a hydroxyapatite coating on a magnesium alloy surface according to claim 1, characterized in that: The surfactant is one or more of sodium dodecylbenzenesulfonate, fatty acid glycerides, and polysorbates.

3. The method for preparing a hydroxyapatite coating on a magnesium alloy surface according to claim 1, characterized in that: The corrosion inhibitor is one or more of hexamethylenetetramine, phosphorus-containing dimethylthiourea, and aldehyde-amine condensate.