Electrodeposition of Calcium Phosphate Coatings on Metallic Substrates for Bone Implant Applications: A Review

Abstract

This review summaries more than three decades of scientific knowledge on electrodeposition of calcium phosphate coatings. This low-temperature process aims to make the surface of metallic bone implants bioactive within a physiological environment. The first part of the review describes the reaction mechanisms that lead to the synthesis of a bioactive coating. Electrodeposition occurs in three consecutive steps that involve electrochemical reactions, pH modification, and precipitation of the calcium phosphate coating. However, the process also produces undesired dihydrogen bubbles during the deposition because of the reduction of water, the solvent of the electrolyte solution. To prevent the production of large amounts of dihydrogen bubbles, the current density value is limited during deposition. To circumvent this issue, the use of pulsed current has been proposed in recent years to replace the traditional direct current. Thanks to breaking times, dihydrogen bubbles can regularly escape from the surface of the implant, and the deposition of the calcium phosphate coating is less disturbed by the accumulation of bubbles. In addition, the pulsed current has a positive impact on the chemical composition, morphology, roughness, and mechanical properties of the electrodeposited calcium phosphate coating. Finally, the review describes one of the most interesting properties of electrodeposition, i.e., the possibility of adding ionic substituents to the calcium phosphate crystal lattice to improve the biological performance of the bone implant. Several cations and anions are reviewed from the scientific literature with a description of their biological impact on the physiological environment.

Evaluation of the Cathodic Electrodeposition Effectiveness of the Hydroxyapatite Layer Used in Surface Modification of Ti6Al4V-Based Biomaterials

“…A smaller Ca/P ratio for samples T5/HA (0.82) and TNF6C/HA (1.13) at 1.5 mA may indicate the formation of a calcium-poor layer. On the surface of titanium alloy T, nanoporous T5, as well as after alkali-sodium treatment of T-S and T5-S, the most similar Ca/P ratio calculated directly from the EDS results to stoichiometric hydroxyapatite Ca/P ratio (1.67) was obtained during hydroxyapatite deposition at 2.5 mA [ 16 , 21 , 24 , 26 ]. In contrast, for TNF6 and TNF72 nanofibrous coatings, the Ca/P ratio is relatively close to the theoretical value during HA deposition at 3.5 mA.…”

“…The search for optimal conditions of the cathodic electrodeposition of HA on the surface of titanium implants/titanium alloys is one of the crucial issues that research on the design and manufacture of modern implants is focused on [ 16 , 30 , 51 , 60 , 61 , 62 ]. Electrodeposition is used in surface engineering electrochemical techniques, in which two electrodes (connected to an electrical generator) are immersed in an aqueous solution containing calcium and phosphate ions [ 16 , 17 , 26 , 63 ]. It should be noted that besides the deposition process conditions, the substrate’s type and properties directly impact the morphology, structure, and mechanical and biological properties of the produced HA layers.…”

“…The plasma spraying, pulsed laser deposition, sol-gel method, PVD (sputter coat-ing), electrophoretic deposition, electrodeposition, and gas detonation deposition are usually used for producing an HA layer on implant surfaces [ 16 , 17 , 21 , 24 , 26 , 27 , 28 ]. Plasma spraying is the most popular, which has the advantage of being able to produce highly repeatable coatings.…”

Antibacterial Electrodeposited Copper-Doped Calcium Phosphate Coatings for Dental Implants

“…For this purpose, several processes have been proposed: plasma spraying, pulsed laser deposition, electrophoretic deposition, soaking process, and electrochemical deposition [ 34 , 35 , 36 ]. Among them, electrodeposition, that is, a wet and low-temperature process, offers major advantages [ 37 ]. Indeed, it allows the treatment of small pieces with complex shapes such as dental implants.…”

Advanced Biomaterials and Coatings

“…As a function of the experimental parameters, various chemical compositions, phases, and morphologies are obtained. Direct current was typically used first, but pulsed current electrodeposition became more interesting in recent years [29]. Since the process takes place in an aqueous medium at room temperature, ionic additives (Na + , Ag + , F, Co 2+ , Cu 2+ , Mg 2+ , Sr 2+ , Zn 2+ , etc.)…”