FR2938271A1 - PROCESS FOR THE ELECTRODEPOSITION OF PHOSPHOCALCIUM COATINGS ON METALLIC SUBSTRATES, COATINGS OBTAINED AND IMPLANTABLE MATERIALS COMPRISING SUCH COATINGS - Google Patents

Abstract

The invention relates to a process for the electrodeposition of phosphocalcic coatings on a metal support comprising the electrolysis of a solution containing calcium ions and phosphate ions. The application of a pulsed electric current between the cathode support and a counter electrode, the electrolyte comprising a solution of Ca (NO), 4H O and NH H PO makes it possible to obtain hydroxyapatite coatings. compact and adhering to the support. The invention also relates to implantable materials comprising such coatings.

Description

The present invention relates to a process for electrodeposition of phosphocalcic coatings on metal substrates, as well as to the coatings obtained and to implantable materials comprising such coatings. BACKGROUND OF THE INVENTION The present invention relates to a process for electroplating phosphocalcic coatings on metal substrates, as well as to the coatings obtained and implantable materials comprising such coatings. . It is known to make prostheses, including hip prostheses and knee, based on metal materials resistant to load and corrosion. Indeed, surgical procedures for the replacement of part or all of a joint (arthroplasty) are more numerous. The implanted and implanted implants are for example orthopedic prostheses, hip prostheses, knee, dental implants or implantable materials in spine surgery. These implants are generally made of metal or metal alloy coated with biomaterials. Indeed, metal alloys mostly adhere to the bone, and this causes friction and generates inflammation. Biomaterials deposited on the prostheses allow the implant to be isolated from its corrosive environment for a certain time in order to improve the welding of the prosthesis to the bone. Among the biomaterials, the family of calcium phosphates is known to constitute bioabsorbable coatings. In particular, hydroxyapatite (PAH) is the subject of research in bone tissue engineering. Indeed, its crystalline structure and its chemical characteristics are similar to those of apatite carbonate found in bone. In order to deposit biomaterials on supports and in particular metal supports, various techniques are known, including sol-gel-associated dip-coating techniques and the technique of plasma torch spraying. This thermal projection technique using a plasma torch allows the production of a layer of hydroxyapatite or porous titanium, in order to improve the bone regrowth around the prostheses. However, poor local adhesion of the coating to the substrate or poor intrinsic cohesion has been observed. These phenomena generate debris difficult to absorb in the body, the presence of which results in premature wear or failure of the anchoring of the implant in the bone. In addition, the reproducibility of these deposits is not always sufficient, which leads to additional manufacturing costs. An alternative is to deposit coatings of various kinds on metal substrates by electrodeposition. It is thus known to produce deposits from precursors including various salts including calcium and phosphorus. These are for example Caio (PO4) 6 (OH) 2 and NaCl in US 5,205,921 in potentiostatic mode or NaCl, CaCl2.2H2O, MgCl2.6H2O, NaHCO3 and Na2HPO4.2H2O in the method described by Lopez-Heredia and al. (1) in direct current, or CaH2 PO4.H2O and CaCl2.2H2O in the method described by Chen et al. (2), in an undefined pulsed mode. In addition, Dumelié et al. (3) performed the electroplating of phosphocalcic coatings in continuous mode from Ca (NO3) 2.4H2O and NH4 (H2PO4). However, the results obtained are still unsatisfactory, and the problem arises in particular to obtain, with good reproducibility, phosphocalcic coatings meeting many criteria: homogeneity in microscopic structure, stoichiometric formula close to that of hydroxyapatite (PAH) crystallographic structure close to that of stoichiometric PAH, hexagonal compact, percentage of crystallinity higher than 90% or even 95%, and having characteristics of good mechanical strength as well as adhesion to the support.

In other words, it is sought to produce phosphocalcic coatings whose crystallographic structure is hexagonal compact, whose formula is similar to that of hydroxyapatite, preferably non-deficient hydroxyapatite, and at temperatures close to room temperature . The present invention relates to the electrodeposition of phosphocalcic coatings on a metal support comprising the electrolysis of an electrolytic solution containing calcium ions and phosphate ions, by applying an electric current between the support forming the cathode and a counter-electrode, wherein the electrolyte comprises a solution of Ca (NO3) 2,4H2O and NH4H2PO4 and the current is applied in pulsed mode. The Applicant has shown that the results obtained according to the demand are interesting from the point of view of the homogeneity and the quality of the coatings obtained by electrodeposition, as well as their qualities in terms of physico-chemical and mechanical properties. This method makes it possible to realize prosthetic coatings at low temperature and to control their thickness and their porosity, to introduce the dopant directly into the electrolytic solution and to vary the rate of substitution of calcium by the dopants contrary to the current methods of elaboration (torch, plasma, CVD , RF magnetron sputtering), to directly control the bioactivity of the coatings through the choice of possible doping ion concentrations (Zn, Mg, Sr, others) in the solution, to make deposits on small pieces of complex shape such as than those used in dental and maxillofacial surgery. In addition, by implementing the method according to the invention, it is possible to obtain phosphocalcic coatings meeting the required criteria of adhesion to the substrate, biocompatibility, crystallinity rate, etc. According to another aspect, the invention relates to phosphocalcic coatings that can be obtained according to the process of the invention, and particularly coatings having a Ca / P ratio of the order of 1.67 0.03, or even 1 0.01. These coatings have a compact hexagonal crystallographic structure and are present at 50% by minimum weight in the form of needles, or agglomerates, for example spheres with a diameter ranging from 1 to 5 μm.

According to another aspect of the invention, this relates to a surgical application material comprising at least one metal part at least partially coated with a coating that can be obtained by the method of the invention. Other advantages and advantageous results will appear in the detailed description and the examples, as well as in the appended figures. Figure 1 schematically shows the electrodeposition material phosphocalcic coating on a metal support. On this diagram, U symbolizes the difference of potential and I the intensity. FIG. 2 represents, as a function of time (t), a current density profile (j) that can be applied during electrodeposition of phosphocalcic coating according to the invention. Figure 3 schematically represents the technique for preparing phosphocalcic coating samples for their scanning electron microscopy (SEM) analysis.

FIG. 4 represents the profile of the potential difference U with the reference electrode applied in Volts (V) in galvanostatic mode, as a function of time t in seconds (s). Figures 5-1 and 5-2 show the scanning electron microscope (SEM) image of the phosphocalcic coating sample obtained in galvanostatic mode at two different magnifications (scale bars: 200 and 5 μm, respectively) . FIGS. 6-1 and 6-2 show the Transmission Scanning Electron Microscope (SEM) image of the same phosphocalcic coating sample, obtained in galvanostatic mode, at two different magnifications (scale bars: 2 μm and 1 μm, respectively). ).

FIG. 7 represents the results of X-ray analysis of the same phosphocalcic coating sample obtained in galvanostatic mode. (Intensity in arbitrary units represented as a function of energy in keV).

FIG. 8 represents the profile of the potential difference U applied (in volts V) as a function of time t in seconds (s) according to the invention. FIGS. 9-1 and 9-2 represent the scanning electron microscope (SEM) image of a phosphocalcic coating sample prepared according to the invention, according to two different magnifications (scale bars: 200 and 5, um respectively). FIGS. 10-1 and 10-2 show the transmission scanning electron microscope (SEM) image of the same phosphocalcic coating sample, obtained according to the invention, according to two different magnifications (scale bars: 2 μm and 0 μm). , 5 pm respectively).

FIG. 11 represents the X-ray analysis results of the same phosphocalcic coating sample obtained according to the invention. (Intensity in arbitrary units represented as a function of energy in keV). FIG. 12 represents the results of X-ray diffraction analysis of the same phosphocalcic coating sample obtained according to the invention. FIG. 13 represents the profile of the potential difference U in volts (V), as a function of time t in seconds (s) according to the invention, in a variant of the process of the invention, in the presence of hydrogen peroxide 6% in volume.

FIG. 14 represents the scanning electron microscope (SEM) image of the phosphocalcic coating sample obtained according to this variant. FIGS. 15-1 and 15-2 show the Transmission Scanning Electron Microscope (SEM) image of the same phosphocalcic coating sample, obtained according to this variant of the invention, according to two different magnifications (scale bars: 1 μm). and 2 respectively).

FIG. 16 represents the X-ray analysis results of the same phosphocalcic coating sample obtained according to this variant of the invention (Intensity in arbitrary units represented as a function of the energy in keV).

FIGS. 17-1 and 17-2 show the image obtained by MEBT microscopy of the untreated (17-1) electrodeposited and treated (17-2) stoichiometric PAH in terms of temperature (scale bars: 600 nm). Electroplating is a common technique for depositing various calcium phosphates.

Such a process is capable of being carried out with the aid of a usual electroplating cell, known as a three-electrode electrodeposition system. Such an electrodeposition device (1) essentially consists of an electrolytic cell equipped with a temperature control device (3), the electrodeposition being carried out in a three-electrode system (4) comprising a against the electrode (5) for example, in graphite or platinum, a saturated calomel reference electrode (6) and a cathode (7). The device is also equipped with a temperature sensor (8). The electrodes and probe are at least partially immersed in the electrolytic solution (9). The metal support constitutes the working electrode (7) and the substrate. By applying a current delivered by the potentiostat / galvanostat a potential difference is created which allows the precipitation in particular of the calcium ions with the phosphate ions on the substrate immersed in the electrolytic solution. The present invention relates to a method for electrodeposition of phosphocalcic coatings on a metal support comprising electrolyzing an electrolytic solution of precursors containing calcium ions and phosphate ions, by applying an electric current between the cathode support and a counter-current. -electrode, characterized in that the electrolyte comprises a solution of Ca (NO3) 2,4H2O and NH4H2PO4, the electric current being applied in pulsed mode. According to the invention, the starting electrolytic solution is a solution comprising essentially precursors Ca (No3) 2,4H2O and NH4H2PO4, preferably 0,042M Ca (NO3) 2,4H2O and 0,025M NH4 (H2PO4). It may also include dopant precursors, as indicated below. By phosphocalcic coating is meant any deposit obtained by electrodeposition, whose molar proportions Ca / P range from 1.5: 1 to 1.7: 1. Preferably according to the invention, the Ca / P molar proportions of the coatings obtained are of the order of 1.67 0.03, or even 1.67 0.01. In the case where the electrolytic solution comprises a dopant precursor, it is the ratio (Ca + dopant) / P which equals this value. In this case, the starting electrolytic solution may comprise from 0.01 to 25 mol% of dopant, preferably up to 13.5%.

For example, for constant molar concentrations 25mM of P in the starting electrolytic solution and (Ca + dopant) of 42mM, the amounts of Ca and dopant are complementary to 42mM. Thus, in the case of zinc doping, it is possible to envisage all solutions, for example Ca / Zn 41.5 / 0.5 or else 40/2 or even 38/4, preferably not more than Zn than 38/4, which corresponds to 13.5% doped solutions. The pH of the electrolytic solution can be adjusted to values between 1 and 6, preferably between 2 and 5. According to the invention, pHs in the range of 3 to 5, preferably 4.4 0, are preferred. 5. To adjust the pH, any suitable mineral base or acid may be used, such as sodium NaOH or hydrochloric acid HCl or any other basic acid suitable for adjusting the pH of the electrolytic solution. The current is applied with a potential difference ranging from 0.01 to 10 V, preferably 0.05 to 2.2 V. The current is applied in pulsed mode according to the invention, with a current density of between 0 , 01 mA / cm2 and 10A / cm2, preferably 0.1 mA / cm2 and 0.1 A / cm2, preferably 1 mA / cm2 and 10mA / cm2.

Preferably, the current density is of the order of 5 mA / cm 2. The profile of the current density applied has been an important factor in the quality of the coatings obtained. Successive cycles comprising an application time td (d for deposition) and a latency time tb (b for break) are applied, with current densities id deposition and jb latency. According to the invention, a given number of cycles td + tb are applied, and a formula makes it possible to determine the particularly advantageous values of the current density j to be applied: ja = (id x td) / (td + tb).

Ja is the average current density. A particularly interesting value of ja is 5 mA / cm 2 0.5. Even more interestingly, five successive cycles were applied, for a total electrodeposition time of 15 minutes, corresponding to the curve shown in FIG. 2. At each cycle and in total, there is twice as much latency than electroplating time. Square pulses can be applied over a period of time ranging from 15 seconds to 2 minutes, preferably from 20 seconds to 1 minute, the ON / OFF ratio being from 1: 50 to 50: 1, preferably 1: 10, and 10: 1. However, other profiles are applicable, which preferably correspond to the formula of ja above. The specialist will be able to adapt the current density profile according to the desired deposit, in particular the shape of the pulses, their duration and the ON / OFF ratio. The temperature of the electrolytic solution is between 15 ° C and 95 ° C, preferably 20 ° C to 80 ° C, more preferably 60 to 65 ° C. After electroplating, the coating may be subjected to air-baking under vacuum or controlled atmosphere. The heat treatment applied after electrodeposition is defined by one or more temperature stages ranging from ambient temperature to a maximum of 1000.degree. C., preferably from ambient temperature to 850.degree. ambient at less than 650 ° C, preferably about 600 ° C, and this for example for a period ranging from 20 minutes to 1:30. For example, the treatment comprises at least one step at a temperature of minus 850 ° C, preferably at 650 ° C.

For example, a temperature of 800 ° C can be applied for about 1 hour. The heat treatment applied can be defined by temperature rises and determined temperature levels, for example as follows: rise of the ambient temperature to a temperature 91 determined between 100 and 200 ° C. at a rate of 0.5 to 10 ° C. / mn, constant temperature bearing 9i for 20 to 120 min, rise in temperature 9l at a temperature 92 determined between 400 and 600 ° C at 0.5 to 10 ° C / min, constant temperature bearing 92 for 20 at 120 min, temperature rise 92 at a temperature 93 determined between 600 and 800 ° C at 0.5 to 10 ° C / min, constant temperature bearing 93 for 20 to 120 min, and followed by a cooling of 93 at room temperature. Preferably, the temperature 93 is limited to 650 ° C. According to a particular embodiment, it is advantageous to introduce hydrogen peroxide into the electrolytic solution. When the electrolyte solution comprises hydrogen peroxide, it is introduced into the electrolytic solution at concentrations of the order of 0 to 30% vol. of hydrogen peroxide relative to the total volume of the starting electrolytic solution. The electrolyte solution comprises from 2 to 10% hydrogen peroxide, preferably 6% by volume. Dopant according to the invention means any type of chemical compound that can be incorporated into phosphocalcic biomaterials, by the addition of precursors in the electrolytic solution. The dopants may be chosen from zinc, magnesium, manganese, silicon, strontium, sodium, silver, titanium and fluorine, and the corresponding precursors capable of liberating, for example, Zn.sup.2 + ions in solution. Mg2 +, Mn2 +, Si4 + Sr2 +, Na +, Ag +, Ti4 + and F "and mixtures thereof Preferably, the dopants are chosen from Zn2 +, Mg2 +, Sr2 + and mixtures thereof As a dopant precursor, it is possible to use according to the invention any salts of the desired dopants capable of being solubilized in an electrolyte solution For example, Zn (NO 3) 2, 4H 2 O may be used to dope the biomaterials with zinc, Mg (NO 3) 2, 6H 2 O for the magnesium dopants, or Sr (NO3) 2 for strontium doping, and their mixtures can also be used With respect to the amount of dopant, it can represent up to about 15 mol% of the amount of Ca in the electrolytic solution. Thus, if a phosphocalcic deposition comprises x mM Ca of the P (Ca / P = z), the dopant in the starting electrolytic solution represents at most 15% of molar x in the electrolytic solution, and in the coating (Ca + dopant) / P = z.

In the coating obtained with doping, there are molar ratios (Ca + dopant) / P = 1.67 0.03, preferably 1.67 0.01. Metallic support according to the invention means any metallic device or at least partially covered by an alloy suitable for producing implant or prosthesis and capable of being coated with phosphocalcic biomaterial. In particular, these metals or metal alloys may be stainless steel, aluminum, titanium or titanium alloys and aluminum or titanium, aluminum and vanadium usual for making such prostheses or implants. In particular, carriers of the Ti6Al4V type are preferred. This titanium alloy (90% Ti - 6% Al - 4% V) is a common component of hip prostheses, which is biocompatible and has good mechanical properties (density 4.4 106g / m3). Preferably, the supports are pretreated before immersion in the electrolytic solution, to prepare their surface, in order to improve the adhesion of the coating. Among these preliminary treatments of the surface of the substrate, mention may be made of chemical etching, for example acid pickling, washing, for example in an ultrasonic bath, degreasing, for example with acetone, rinsing, for example with distilled water and / or surface modification by abrasion, for example sanding with alumina beads or with hydroxyapatite powder, polishing with abrasive paper.

Among these preliminary treatments, it is preferably carried out according to the invention an acid pickling, an alumina sanding with alumina balls with a diameter of between 100 and 300 μm, until a roughness of the order of 5 μm, preferably 3 μm, preferably 2 μm, followed by sonication in acetone.

Any other suitable conventional treatment or pretreatment sequence may nevertheless be provided, provided that a sufficiently clean and abraded surface for satisfactory subsequent deposition. According to the invention, by surface pretreatment is preferably meant any chemical or physical preparation treatment, with the exception of sol-gel phosphocalcic deposition. The invention also relates to phosphocalcic coatings obtainable by the method of the application. The analyzes of the coatings obtained reflect particularly interesting characteristics of the coatings. Thus, coatings having a Ca / P or (Ca + dopant) / P ratio of about 1.67 can be obtained, ie the typical ratio of pure hydroxyapatite without deficit. Furthermore, the deposited coatings are of uniform quality. They consist essentially of hydroxyapatite, in particular of non-deficient hydroxyapatite which is at least 50%, preferably 70% in the form of needles of dimensions of between 10 nm and 5 μm, in particular 100 nm and 2 μm in length. and between 5 nm to 200 nm wide, including 10nm to 100nm. In particular, when a heat treatment has been applied to the coating after deposition, the needles may disappear to give crystallites or crystallized spherical or pseudospheric particles. These particles have individual dimensions of the order of 5 to 250 nm. These particles can be grouped, with good cohesion between these spheres or pseudospheres. Thus, the coatings of the invention may be essentially crystalline particles or spherical or pseudospheric crystallized particles, of individual dimensions of the order of 5 to 250 nm, especially 20 nm to 100 nm, these particles may be grouped in a cohesive manner. The coatings obtained are compact and cohesive, and they adhere to the metal substrate satisfactorily. Thus, the Applicant has been able to obtain compact coatings which adhere well to the surface, that is to say they are sufficiently cohesive at the same time and adhesive. In addition, they have the advantage of being able to present, particularly as a function of doping, good properties in terms of biocompatibility. The invention also relates to bone surgical application equipment comprising at least one metal part covered at least partially with a coating that can be obtained by the electroplating method according to the invention. As a surgical application material is meant according to the invention metal prostheses or implants or more broadly any implantable at least partially metallic device at least partially covered biomaterials that can be obtained by the method of the present application. It may be any medico-surgical implantable at least partially metallic material, for example bone implants, dental implants, articular or non-articular bone prostheses, including bone plates or screws, and that the biological fixation of the implant is provided in the cortical or spongy bone. These materials can be used, for example, during hip prosthesis, knee surgery, spine, shoulder, ankle, elbow, hand, foot, and used in reconstructive surgery, osteosynthesis or dental surgery. or orthopedic.

EXAMPLES Example 1 The electrolytes were prepared by mixing a solution of 0.042 M Ca (NO3) 2.4H2O and 0.025 M NH4 (H2PO4). The pH value was adjusted to 4.4 by adding a solution of NaOH. Ti6Al4V substrates selected were platelets of 10mm x 10mm x 0.6mm. The surfaces were shot blasted with alumina particles to obtain an average roughness ranging from 1 μm to 4 μm. Before depositing the coating, the substrates were immersed in a mixture of nitric and hydrofluoric acid (HNO 3 6% by volume and HF 3% by volume). Samples were sonicated in acetone and demineralized water. EXAMPLE 1 is comparative, it is carried out in galvanostatic mode, according to the potential difference profile of FIG. 4. EXAMPLE 2 The electroplating was carried out with a pulsed current as defined in FIG. 2. Deposition time td: 1 minute, at a current density Jd of 15 mA / cm 2, followed by a rest time tb: 2 minutes, at current density jb: zero. The average current density Ja was therefore 5 mA / cm 2. Five cycles were performed, corresponding to a total deposition treatment time of 15 minutes. Example 3 Materials and Methods 3.1 Scanning Electron Microscopy The morphology of the coatings was observed using a LaB6 electronic microscope (JEOL JSM-5400LV) operating between 0-30 kV. The microscope has been associated with an X-ray microanalysis device (ulra-thin window Si (Li)). The samples were coated with an Au-Pd conductive layer for scanning electron microscopy and C for X microanalysis. The X-ray spectra were made at 15 kV with an acquisition time of 100 s.

For quantitative analysis, the measurements were performed three times to obtain an average value of the Ca / P rate. 3.2 For transmission electron microscopy (SEM), a Philips CM30 microscope operating between 100 and 300 kV was used to study the morphology of samples at the nanometer level. A specific sample was made using an EPON resin (AGAR 100 RESIN kit, Oxford Instruments France). The preparation of the analysis consists of the steps shown schematically in FIG. 3. The CaP coating 13 deposited on a metal support 14 is impregnated with resin without hardening, in a first step (1), to give the sample 16 where a resin layer 15 is deposited on the coating 13 deposited on the metal support 14. By immersion, in a second step (2), in a bath of liquid nitrogen 17 which causes a thermal shock, the metal support 14 separates from the coating 13 At this stage, the sample 18 at the outlet (3) of the bath of liquid nitrogen consists only of the phosphocalcic coating 13 included in the resin 15. Ultra-thin sections of the order of 100 nm, were cut with a diamond blade with an ultramicrotome. The ultra-fine debited sections obtained 19 are recovered and arranged (5) on the copper grid (20) where they were covered with a conductive layer of carbon and were observed at a voltage of 250 kV. 3.3 X-ray diffraction analysis The phosphocalcic powders are scraped from electroplated coatings and their phase composition analyzed by X-ray diffractometer (Brucker D8 Advance). The spectra were collected with CuKa radiation (29 = 10 to 45 °); not 0.04 °; 12 seconds at each step. Example 4 = analysis of the sample obtained in galvanostatic mode according to the profile of FIG.

As shown in Figure 5, holes and craters are present, attributed to H2 bubbles.

At high resolution, however, it appears that the coating is composed of sharp needles. These observations confirm the SEM micrographs of Figure 6 which indicate that the needles are of the order of 1 μm in length and 0.1 μm in width. The X-ray analysis of the coatings reveals a Ca / P content of 1.54 0.03 (FIG. 7). Under these conditions, hydroxyapatite deficient in calcium is obtained. Example 5: Analysis of the sample obtained in pulsed mode.

As shown in FIGS. 2 and 8, 5 cycles were applied, each cycle has two minutes of pause and one minute of deposition. One cycle is represented by the sequence: j = 0 mA / cm2 and Eljbre = + 350 mV, for 2 minutes, then j = 15 mA / cm2, for 1 minute, with a starting potential of about -2.2 V For each cycle, the variation of potential as a function of time is similar to the curve of FIG. 4 and represented in FIG. 8. By comparison of the micrographs obtained (FIGS. 9 and 10) with micrographers of FIG. that the number of holes and craters is reduced and the coating composed of small needles and crystallites.

The SEM analysis of Figures 10-1 and 10-2 confirms these observations and shows needles less than 0.2 μm in size. The X-ray measurements (FIG. 11) give a Ca / P level of 1.66 0.01 corresponding to the stoichiometric hydroxyapatite. These results are confirmed by Fig. 12, which shows typical diffraction peaks at 20 = 25.9 ° -31.8 ° -32.2 ° -32.9 ° -34 ° -39.8 ° corresponding to stoichiometric hydroxyapatite from standard databases. EXAMPLE 6 Electrodeposition is carried out as above in Example 2, in the presence of hydrogen peroxide in the electrolyte (6% by volume), with

a current density d i of 5 mA per cm 2. The variation of the potential as a function of time is shown in FIG. 13. The morphology of the coating obtained (FIGS. 14 and 15) is without hole or crater.

Agglomerated needles in crystallite (sphere about 2 μm in diameter) appear. The coating is dense and compact. X analysis (Figure 16) reveals a ratio of Ca / P of 1.67 to 0.01. EXAMPLE 7 The coating obtained in Example 6 (H 2 O 2) was heat-treated in an oven at 800 ° C. for one hour. The needle morphology of the coating is transformed after heat treatment into spherical crystallized particles or pseudo-spherical interconnected which appear in Figure 17.

REFERENCES (1) M. Lopez-Heredia et al. ; J Sci Mater: Mater Med (2007) 18: 381-390; (2) Chen Xing-yu et al. ; Trans. Nonferrous Met. Soc. China 17 (2007) 5,617-621; (3) N. Dumelié, H. Benhayoune, D. Richard, D. Laurent-Maquin, G. Balossier; Material Characterization 59 (2008) 129-133.

Claims (23)

REVENDICATIONS1. A process for the electrodeposition of phosphocalcic coatings on a metal support comprising the electrolysis of an electrolyte solution containing calcium ions and phosphate ions, by applying an electric current between the cathode support and a counter-electrode, characterized in that the electrolyte comprises a solution of Ca (NO3) 2,4H2O and NH4H2PO4 and the current is applied in pulsed mode. 2. electroplating process according to claim 1, characterized in that the molar proportions Ca / P obtained range from 1.5 to 1.7, preferably 1.67 0.03. Electroplating method according to claim 1 or 2, characterized in that the current is applied with a potential difference of 0.01 to 10 V, preferably 0.05 to 2.2 V. 4. electroplating process according to one of claims 1 to 3, characterized in that the current is applied with a mean current density over a cycle of between 0.01 mA / cm 2 and 10 A / cm 2, preferably 0, 1 mA / cm 2 and 0.1 A / cm 2. Electroplating method according to one of Claims 1 to 4, characterized in that the current is applied with a mean current density over a cycle of between 1 mA / cm 2 and 10 mA / cm 2, preferably 0.5 mA / cm2. 6. electroplating process according to one of claims 1 to 5, characterized in that the temperature of the electrolytic solution is between 15 ° C and 95 ° C, preferably 20 ° C to 80 ° C. 7. electroplating process according to one of claims 1 to 6, characterized in that the pH of the electrolytic solution is between 1 and 6, preferably between 2 and 5. 8. electroplating process according to one of claims 1 to 7, characterized in that the heat treatment applied is defined by at least one temperature step at a temperature of less than 850 ° C, preferably at a temperature below 650 ° C. 9. electroplating process according to one of claims 1 to 8, characterized in that the heat treatment applied is defined by the following temperature rises and temperature stages: rise of the ambient temperature to a temperature 0, determined between 100 and 200 ° C at a rate of 0.5 to 10 ° C / min, steady temperature bearing 01 for 20 to 120 min, rise in temperature 61 to a temperature O 2 determined between 400 and 600 ° C at 0, 5 to 10 ° C / min, constant temperature bearing 02 for 20 to 120 minutes, rising temperature 02 at a temperature 03 determined between 600 and 800 ° C at a rate of 0.5 to 10 ° C / min, temperature step constant 03 for 20 to 120 minutes, followed by a cooling of 03 at room temperature. 10. electroplating process according to one of claims 1 to 9, characterized in that the current applied in pulsed mode with an intensity of between 0.1 mA / cm 2 and 0.1 A / cm 2, preferably between 1 mA / cm 2 and 10mA / cm 2, the pulses being of square shape in a range of allanr period of 15 s to 2 min, preferably 20s to 1 min, the ON / OFF ratio being between 1: 50 and 50: 1, preferably 1 : 10 and 10: 1. 11 electroplating process according to one of claims 1 to 10, characterized in that the electrolyte solution comprises from 1 to 30% by volume of hydrogen peroxide. 12.Electrodeposition process according to one of claims 1 to 11, characterized in that the electrolyte solution comprises from 2 to 10% hydrogen peroxide, preferably 6% by volume. 13. electroplating process according to one of claims 1 to 12, characterized in that the starting electrolyte solution comprises from 0.01 to 25 mol% of dopant. 14. electroplating process according to one of claims 1 to 13, characterized in that the dopant is selected from Zn2 +, Mg2 +, Mn2 +, Si4 + Sr2 +, Na +, Ag +, Ti4 +, F- and mixtures thereof. 15. electroplating process according to one of claims 1 to 14, characterized in that the dopant is selected from Zn, Mg, Sr, or mixtures thereof. 16. An electroplating method according to one of claims 1 to 15, characterized in that the dopant is incorporated in the electrolytic solution as Zn (NO3) 2,4H20; Mg (NO3) 2.6H2O; Sr (NO3) 2 and mixtures thereof. 17. electroplating process according to one of claims 1 to 16, characterized in that the support is based on titanium, aluminum, vanadium, stainless steel or mixtures thereof. 18. Electroplating process according to one of claims 1 to 17, characterized in that the support is of the Ti6AI4V or Ti type. 19. electroplating process according to one of claims 1 to 18, characterized in that the starting electrolyte solution comprises 0.042 M Ca and 0.025 M P, or 0.042 M of (Ca + dopant) and 0.025M P . 20. Coating obtainable by the method according to one of claims 1 to 19, and having a structure comprising at least 50%, preferably 70% phosphocalcic compound in the form of needles of length ranging from 10 nm to 0.5 μm, preferably 100 nm to 2 μm and width ranging from 5 nm to 200 nm, preferably 10 nm to 100 nm. 21. The coating of claim 20, characterized in that the molar proportions Ca / P or (Ca + dopant) / P obtained range from 1.5 to 1.7, preferably 1.67 0.03. 22. The coating of claim 20 or 21, characterized in that it is formed of crystalline particles or spherical or pseudospheric crystallized particles, of individual dimensions of the order of 5 to 250 nm, these particles can be grouped in a cohesive manner. 23. Implantable material comprising at least one metal part at least partially covered with a coating according to one of claims 20 to 22, or obtainable by the process according to claims 1 to 19.