Phosphate Coatings Research Articles

Composition and morphology of calcium phosphate coatings formed on resorbable substrates based on pure Mg and Mg-HAp composite

Composition and morphology of calcium phosphate coatings formed on resorbable substrates based on pure Mg and Mg-HAp composite

Effect of Graphene Oxide Addition on the Anticorrosion Properties of the Phosphate Coatings in Neutral and Acidic Aqueous Media.

Highlights What are the main findings? GO improves the anticorrosion properties of the zinc phosphate coatings in neutral media, and disimproves them in acidified media. What is the implication of the main finding? The acidity of the media should be taken into account when using GO-containing zinc-phosphate coatings. Graphene oxide (GO) is an advanced additive improving the properties of various types of coatings and intensifying the deposition process. In this work, GO is used as an additive to the traditional phosphating solution of the widely used Russian low-carbon steel 08YU (DC04). The anticorrosion properties of the obtained phosphate coatings were investigated in neutral (0.5 M NaCl) and acidified (0.1 M Na2SO4 + 0.02 M H2SO4) aqueous solutions. Increasing the GO concentration in the phosphating solution to 0.3 g/L was found to improve the anticorrosion properties of the phosphate coatings in neutral NaCl solutions. At the same time, in acidified Na2SO4 solutions, the corrosion rate of 08YU steel with phosphate coatings increased as a function of the GO concentration. It is assumed that a possible reason for various corrosive behavior is the influence of the GO plates distributed in the coating on the rate of the oxygen or hydrogen reduction reactions.

Controllable phases evolution and properties of zinc-phosphate/strontium‑zinc-phosphate composite conversion coatings on Ti: Effect of temperature

Bioactive phosphate coatings based on hopeite (HP, Zn3(PO4)2·4H2O) and strontium‑zinc-phosphate (SZP, SrZn2(PO4)2) phases have attracted extensive attention in the surface modification of metallic implants. Nevertheless, further clarifications on the synergistic effect of HP and SZP, as well as the phase evolution between them are still needed. Herein, a chemical conversion technique was utilized to prepare composite phosphate coatings containing HP and SZP on titanium (Ti). The effect of phosphating temperature on the phase, properties, and deposition mechanism of the coatings was investigated. The results showed that the coating obtained at 50 °C was composed of HP with minor SZP crystals, while their relative contents were reversed at 80 °C. The elevated temperature also changed the crystal morphology of SZP from ellipsoidal to cubic. These variations could be attributed to the enhanced priority of Sr and Zn ions to form bimetallic-phosphate (SZP), which has a different lattice structure from HP crystal. In addition, the HP/SZP composite coating formed at 60 °C exhibited superior comprehensive properties like roughness, wettability, bonding strength, ion release, and corrosion resistance. Overall, this study elucidates the temperature-induced phase evolution and properties of HP/SZP composite coatings, which facilitates the optimal regulation of phase composition to achieve desired properties.

The effect of protective and decorative coatings on the strength of adhesive joints of hot-dip galvanized steel sheets

The influence of chromate, phosphate, glossy and brightening coatings on the performance of adhesive joints of hot-dip zinc-coated steel sheets was compared. The contribution of this study has been to compare the adhesive joint strength in adherends with two types of coatings: steel sheet with zinc coating and additional coating. Two types of bisphenol A (BPA) epoxy adhesives were used to assemble the joints, that were subject to shear stresses. The surface of the adherends was described in terms of surface roughness parameters. The highest value of the shear strength was recorded for the adhesive joints of the hot-dip zinc-coated steel sheets with chromate passivation and brightening. The poorest performing joints were of the glossy galvanized steel sheets.

Preparation of Zn-Ca Phosphate Coating in Presence of PTFE on 45 Steel and its Corrosion Properties in Simulated Seawater

Preparation of Zn-Ca Phosphate Coating in Presence of PTFE on 45 Steel and its Corrosion Properties in Simulated Seawater

Li2TiO3 Dopant and Phosphate Coating Improve the Electrochemical Performance of LiCoO2 at 3.0–4.6 V

A sol–gel tandem with a solid-phase modification procedure was developed to synthesize Li2TiO3-doped LiCoO2 together with phosphate coatings (denoted as LCO-Ti/P), which possesses excellent high-voltage performance in the range of 3.0–4.6 V. The characterizations of X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy illustrated that the modified sample LCO-Ti/P had the dopant of monoclinic Li2TiO3 and amorphous Li3PO4 coating layers. LCO-Ti/P has an initial discharge capacity of 211.6 mAh/g at 0.1 C and a retention of 85.7% after 100 cycles at 1 C and 25 ± 1 °C between 3.0 and 4.6 V. Nyquist plots reflect that the charge transfer resistance of LCO-Ti/P after 100 cycles at 1 C is much lower than that of the spent LCO, which benefits Li-ion diffusion. Density functional theory calculations disclose the superior lattice-matching property of major crystal planes for Li2TiO3 and LiCoO2, the lower energy barriers for Li-ion diffusion in Li2TiO3, and the suppressed oxygen release performance resulting from phosphate adsorption. This work provides useful guidance on the rational design of the high-voltage performance of modified LiCoO2 materials in terms of lattice-matching properties aside from the phosphate coating to reduce the energy barriers of Li-ion diffusion and enhance cycling stability.

In situ growth of Ca-Zn-P coatings on the Zn-pretreated WE43 Mg alloy to mitigate corrosion and enhance cytocompatibility

Magnesium (Mg) alloys are potential materials for orthopedic fixation devices but rapid degradation of the materials restricts wider clinical applications. Herein, zinc-incorporated calcium phosphate (Ca-Zn-P) coatings are prepared on the Zn-pretreated WE43 Mg alloy by a hydrothermal technique under relatively stable and favorable conditions. The hydrothermal coating consists of a compact bottom layer of CaZn2(PO4)2∙2 H2O and ZnO granular crystals and a jagged upper layer of CaHPO4. The Zn coating reduces the corrosion current density of WE43 to (3.49 ± 1.60) × 10−5 A cm−2, whereas the Ca-Zn-P/Zn composite coating further reduces it by 3 orders of magnitude in the simulated body fluid (SBF). The charge transfer resistances of the Zn-coated and Ca-Zn-P/Zn-coated alloys increase by 49 and 7176 times to 835 and 1.22 × 105 Ω cm2, respectively. The 7-day immersion results reveal that the Zn coating cannot provide long-term protection to WE43 in SBF because of the formation of galvanic couples between the Zn coating and WE43. In contrast, Ca-Zn-P/Zn-coated WE43 remains intact after soaking for 7 days and furthermore, the Ca-Zn-P coating self-repairs and continues to grow despite dissolution. The compact and adherent Ca-Zn-P bottom layer plays a major role in mitigating corrosion of WE43 by hindering penetration of the aggressive medium and charge transfer of the corrosion reactions resulting in only slight corrosion of the Zn layer. Biologically, the Zn coating reduces attachment and proliferation of MC3T3-E1 pre-osteoblasts on WE43, but the composite coating fosters cell adhesion and proliferation which stems from the good biocompatibility of the hydrothermal layer and relatively stable surface conditions avoiding severe corrosion.

Effect of amorphous calcium phosphate coatings on tribological properties of titanium grade 4 in protein-free artificial saliva

Progress in dental implant prosthetics largely depends on developing new biomaterials and understanding the complex processes of their tissue adaptation. The related tribological wear phenomena within the dental system determine the durability and quality of the newly developed dental biomaterials. This paper presents an assessment of the tribological wear of the amorphous calcium phosphate (ACP) coatings on the commercially pure titanium Grade 4 (CpTi G4) substrate subjected to sandblasting and autoclaving in artificial saliva. The ACP coatings were produced using electrochemically assisted deposition (ECAD). The tribological properties were studied in a reciprocating motion in the system of ball-on-disc in protein-free artificial saliva. The surface morphology and chemical composition was characterized using the SEM and EDS method, respectively. The surface wettability was tested using the sitting drop in the air. It was found that the presence of the ECAD-derived ACP coating increases surface roughness, local contact potential difference, surface wettability, and resistance to tribological wear of CpTi G4 substrate significantly improving its service life. The tribological wear of CpTi G4/ACP occurred according to the three-body abrasion wear mechanism, in which artificial saliva played a key role as a biological lubricant.

A trace amount of MXene@PDA nanosheets for low-temperature zinc phosphating coatings with superb corrosion resistance

In this study, MXene nanosheets were functionalized by polydopamine to fabricate MXene@PDA (PMX) hybrid nanomaterial as an accelerator for low-temperature phosphating. PMX structure had a large specific surface area and the dispersibility of PMX in the phosphating bath was higher than that of MXene. The phosphate coating obtained by introducing 0.025 g/L PMX (0.025-PMX coating) into the phosphating bath showed excellent comprehensive properties compared to past reports of nanomaterials used as accelerators since 2010. The phosphate coating was 81.52% heavier in mass per unit area and 98.93% lower in porosity than the pure phosphate coating. Furthermore, electrochemical impedance spectroscopy (EIS) data showed that the |Z0.01 Hz| of 0.025-PMX coating was approximately two orders of magnitude higher than that of the pure coating. Subsequently, we proposed a mechanism for the positive impact of trace amounts of PMX nanosheets on phosphate coatings. This study demonstrates the importance of further studying nanomaterials as phosphating accelerators.

Amorphous Precursor-Mediated Calcium Phosphate Coatings with Tunable Microstructures for Customized Bone Implants.

Calcium phosphate (CaP) is frequently used as coating for bone implants to promote osseointegration. However, commercial CaP coatings via plasma spraying display similar microstructures, and thus fail to provide specific implants according to different surgical conditions or skeletal bone sites. Herein, inspired by the formation of natural biominerals with various morphologies mediated by amorphous precursors, CaP coatings with tunable microstructures mediated by an amorphous metastable phase are fabricated. The microstructures of the coatings are precisely controlled by both polyaspartic acid and Mg2+ . The cell biological behaviors, including alkaline phosphatase activity, mineralization, and osteogenesis-related genes expression, on the CaP coatings with different microstructures, exhibit significant differences. Furthermore, in vivo experiments demonstrate the osseointegration in different types of rats and bones indeed favors different CaP coatings. This biomimetic strategy can be used to fabricate customized bone implants that can meet the specific requirements of various surgery conditions.

Preparation and anticorrosion properties of electrodeposited calcium phosphate (CaP) coatings on Mg–Zn–Ca metallic glass

In order to improve the corrosion resistance and bioactivity of Mg–Zn–Ca metallic glass, a series of calcium phosphate (CaP) coatings were synthesized on Mg66Zn30Ca4 metallic glass via the electrodeposition method in this paper. As compared with the Mg-based metallic glass, the electrodeposited CaP coatings show considerable improvement in corrosion resistance and bioactivity. Based on the experimental results, the formation and anti-corrosion mechanisms of CaP coatings were proposed, suggesting that electrodeposited CaP coating can promote the precipitation of calcium phosphate and thereby induce the mineralization process. By constructing the predominance area diagram, the relationship between the composition of the CaP solution and the precipitation process of calcium phosphate (CaHPO4·2H2O, Ca5(PO4)3OH) at 25 °C was accurately described. These results provide insights into the electrodeposition process of CaP type coatings.

UMAOH Calcium Phosphate Coatings Designed for Drug Delivery: Vancomycin, 5-Fluorouracil, Interferon α-2b Case.

Drug delivery systems based on calcium phosphate (CaP) coatings have been recently recognized as beneficial drug delivery systems in complex cases of bone diseases for admission of drugs in the localized area, simultaneously inducing osteoinduction because of the bioavailable Ca and P ions. However, micro-arc oxidation (MAO) deposition of CaP does not allow for the formation of a coating with sufficient interconnected porosity for drug delivery purposes. Here, we report on the method to deposit CaP-based coatings using a new hybrid ultrasound-assisted MAO (UMAOH) method for deposition of coatings for drug delivery that could carry various types of drugs, such as cytostatic, antibacterial, or immunomodulatory compositions. Application of UMAOH resulted in coatings with an Ra roughness equal to 3.5 µm, a thickness of 50–55 µm, and a combination of high values of internal and surface porosity, 39 and 28%, respectively. The coating is represented by the monetite phase that is distributed in the matrix of amorphous CaP. Optimal conditions of coating deposition have been determined and used for drug delivery by impregnation with Vancomycin, 5-Fluorouracil, and Interferon-α-2b. Cytotoxicity and antimicrobial activity of the manufactured drug-carrying coatings have been studied using the three different cell lines and methicillin-resistant S. aureus.

Calcium phosphate coating formed on titanium scaffold by plasma electrolytic oxidation

The article provides the results of the preparation of calcium phosphate coatings by plasma electrolytic oxidation. Calcium phosphate coatings are formed on titanium scaffolds with a porous structure. Titanium scaffolds are products of additive manufacturing equipment by selective laser melting. The morphology of the obtained coating, phase and elemental composition are described, the Ca/P ratio of the coating is dete rmined. The surface of the scaffold is porous due to the baking of powder particles during production. XRD analysis shows the presence of calcium phosphate and oxide compounds. The resulting oxide coating is evenly distributed over the porous surface of the scaffold. Titanium, aluminum and vanadium are located in the areas of the coating free of calcium phosphate particles. The average Ca/P ratio for the resulting coating was 2.48. This value is close to the Ca/P ratio in human bone. It is concluded that the use of the PEO method is promising for the manufacture of scaffolds with a porous structure with calcium phosphate coatings for use in traumatology and orthopedics. The use of titanium scaffolds with a porous structure with calcium phosphate coatings will improve the osseointegration of implants and exclude the possibility of implant failure.

Calcium phosphate coating formed on titanium scaffold by plasma electrolytic oxidation

The article provides the results of the preparation of calcium phosphate coatings by plasma electrolytic oxidation. Calcium phosphate coatings are formed on titanium scaffolds with a porous structure. Titanium scaffolds are products of additive manufacturing equipment by selective laser melting. The morphology of the obtained coating, phase and elemental composition are described, the Ca/P ratio of the coating is dete rmined. The surface of the scaffold is porous due to the baking of powder particles during production. XRD analysis shows the presence of calcium phosphate and oxide compounds. The resulting oxide coating is evenly distributed over the porous surface of the scaffold. Titanium, aluminum and vanadium are located in the areas of the coating free of calcium phosphate particles. The average Ca/P ratio for the resulting coating was 2.48. This value is close to the Ca/P ratio in human bone. It is concluded that the use of the PEO method is promising for the manufacture of scaffolds with a porous structure with calcium phosphate coatings for use in traumatology and orthopedics. The use of titanium scaffolds with a porous structure with calcium phosphate coatings will improve the osseointegration of implants and exclude the possibility of implant failure.

Preparation of Calcium Phosphate Compounds on Zirconia Surfaces for Dental Implant Applications.

Titanium is widely used in medical implants despite the release of heavy metal ions over long-term use. Zirconia is very close to the color of teeth; however, its biological inertness hinders bonding with bone tissue. Alkaline treatment and coatings of calcium phosphate can be used to enhance bone regeneration adjacent to dental implants. This study examined the effects of alkaline treatment, calcium phosphate coatings, and sintering, on the physical properties of implant material. Our analysis confirmed that the calcium phosphate species were octacalcium phosphate (OCP). The sintering of calcium phosphate was shown to create B-type HAP, which is highly conducive toward the differentiation of mesenchymal stem cells (MSCs) into osteoblasts for the facilitation of bone integration. Conclusions: This study demonstrated the room-temperature fabrication of dental implants with superhydrophilic surfaces to enhance biocompatibility.

The influence of silicon on the formation of phosphate coatings for low-carbon IF steels

It is essential to clarify the influence of silicon on the phosphating process for low-carbon IF steels. In the present work, the formation of phosphate coatings for the IF steels with 0.01 wt%, 0.1 wt% and 0.5 wt% silicon was experimental determined by the combination of electrochemical characterization with X-rays photoelectron spectroscopy (XPS), focused Ion beam and transmission electron microscope (FIB-TEM), X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis. It was confirmed that the silicon layer formed on the IF steels surface was mainly composed by Si, SiO2, SiC, Si3+ and oxides of Fe. Thicker silicon layers were formed with the increase of silicon concentrations, which inhibited the electrochemical reaction on the steels surface during the phosphating process. The diffusion of the ions including Me2+, PO43− and H+ to the surface of the substrate was severely restricted by the thick silicon layer, leading to the deterioration of the phosphating performance. The influence mechanism of silicon was finally proposed for a deep understanding of the phosphating process for IF steels.

Influence of a Constant Perpendicular High Magnetic Field on the Electrodeposition of Calcium Phosphate Coating

Calcium phosphate coatings were formed on a Ti6Al4V substrate by electrodeposition under a high magnetic field up to 16 T. The magnetic field was parallelly applied to the vertical surface electrode. Changes in crystal morphology of calcium phosphates were investigated as a function of the magnetic field amplitude, and the results are discussed in terms of magnetic field effects. Magnetohydrodynamic convection due to the Lorentz force could considerably reduce the formation of volcano-like structures and generate more uniform deposits without changing Ca/P ratios.

Composition and structure of calcium-phosphate coatings on Ti3AlC2 produced by sol-gel synthesis

Calcium phosphate materials have been widely used in medical practice for decades. Due to their bioactivity and integration with human hard tissues. They have been produced in the form of dense and porous ceramics, powders and needle-like crystals (whiskers). Despite the high mechanical properties (hardness, compressive strength), calcium phosphate ceramics are mainly used in medicine mainly as the fillers for bone defects formed due to injuries or diseases because they have high fragility and low crack resistance. These circumstances do not allow using them in the sites that have high mechanical loads (e.g. hip surgery). To solve these problems metal implants are used. Among them, Ti-based alloys are the most widely used due to its high mechanical properties, biocompatibility and high corrosion resistance. Recently, the data on the use of MAX phases as medical materials to create the composites based on Ti3SiC2 have appeared in the literature. Calcium phosphate coatings were obtained on Ti3AlC2 substrate by the sol-gel method. The effect of temperature, holding time, chemical compositions of reactants on the phase composition and structure of the samples are discussed. XRD measurements have revealed that the initial coatings consists of nanoparticles sized 10-50 nm. Light and scanning electron microscopy (SEM) were applied to study the morphology of the coatings. It have been shown that the coatings had thickness in an interval 40-100 mm and had the homogenous structure. It has been established by X-ray phase identification that the coating after heating at 1000oC during 1 hour contained b-tricalcium phosphate (b-TCP). It was found, that the thickness and phase composition of coatings depend on the time of coating in calcium phosphate solution. The optimal conditions for the formation of coatings are established.

Effect of aluminium oxyhydroxide nanoparticles on the structure and properties of the calcium phosphate coatings

Modification of calcium phosphate (C-P) based biocoatings with aluminum oxyhydroxide AlO(OH) nanoparticles and its effect on their morphology, structure, phase composition, wettability, electrical and biological properties are studied. C-P coatings were formed on the titanium substrate by the microarc oxidation (MAO) method in the acidic electrolyte. Porous calcium-phosphate coatings were functionalized by aluminum oxyhydroxide nanoparticles by hydrolysis reaction in aqueous suspension of AlN nanopowder. The increase ultrasonic dispersion duration of AlN suspension up to 60 min provides more uniform distribution of AlO(OH) on the coating surface. The introduction of positively charged AlO(OH) nanoparticles has been unveiled to increase zeta potential value of the coating surface. The antimicrobial activity of the C-P coating rises by 27% after the introduction of AlO(OH) nanoparticles and the proliferation of L929 cells on the coatings functionalized by the nanoparticles grows by 25%. The results obtained demonstrate the aluminum oxyhydroxide nanoparticles introduction significantly improve the functional properties of the C-P coatings.

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

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.