Effect of Post-Treatment Techniques on Corrosion and Wettability of Hydroxyapatite-Coated Co–Cr–Mo Alloy

Abstract

This study is a comparison between the effect of sintering and alkaline post-treatment techniques on calcium phosphate-coated Co-Cr-Mo alloy in terms of electrochemical corrosion behavior and wettability. The Co-Cr-Mo substrates were electrophoretically coated by calcium phosphate in a solution of Ca(NO 3 ) · 4H 2 O and NH 4 H 2 PO 4 . The sintering and alkaline post-treatment techniques were then conducted to convert an as-deposited dicalcium phosphate dihydrate phase to crystalline hydroxyapatite (HA). The coated layers were characterized in terms of phase, crystallinity and composition using X-ray diffraction, Fourier transform infrared spectroscopy and energy-dispersive spectroscopy. In addition, morphology and thickness of coated layers were evaluated using a scanning electron microscope. The results indicate HA-coated samples with a sintering post-treatment technique exhibit more improvement in corrosion parameters, such as corrosion potential (E corr ) and corrosion current density (I corr ), but lower enhancement in hydrophilicity. However, the HA-coated samples with an alkaline posttreatment technique reveal higher hydrophilicity with lower improvement in corrosion resistance.

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications

“…For example, in magnesium alloys, sintering post-treatment is not possible due to the low melting point of the substrate [832]. As an alternative, alkaline post-treatment is often used.…”

“…Heat treatment, usually at 600–800 °C for 1 h, transforms the water trapped in the coating during deposition processes such as sputtering, ED, EPD and PS into ions, thus stabilizing the crystalline structure [ 49 ]. Shirdhar et al [ 832 ] investigated the influence of those two post-treatments on Co-Cr-Mo alloy EPD with CaP coating. XRD analysis confirmed that the majority of the DCPD phases initially deposited on the surface transformed to crystalline HAp after either sintering or alkaline post-treatment.…”

“…While sintering is a good way to convert low CaP phases to crystalline HAp and minimize porosity by increasing the coating density, it is not applicable in some cases. For example, in magnesium alloys, sintering post-treatment is not possible due to the low melting point of the substrate [ 832 ]. As an alternative, alkaline post-treatment is often used.…”

Evaluating hydrothermal synthesis of fluorapatite nanorods: pH and temperature

“…The ANOVA table for the shape is presented in Table 3. Values less than 0.050 for 'Prob > F' indicate that the model is significant, which is desirable as it reveals that the terms in the model have a significant effect on the response [17,18]. The Model F-value of 16.50 implies that the model is significant.…”

A Microarray Screening Platform with an Experimental Conditions Gradient Generator for the High-Throughput Synthesis of Micro/Nanosized Calcium Phosphates

“…The morphology and structure of micro/nanosized biomedical materials also play a crucial role in their properties and applications [4,5]. Research has shown that a flake-like CaP coating on an alloy is beneficial for the improvement of osseointegration [6], and hydroxyapatite (HAp) nanorods can self-assemble to enamel-like structures [7] and sphere nano alginate/HAp that could promote bone mineral deposition [8]. However, most studies that have been reported have been based on the traditional trial and error method, namely the use of existing theoretical and empirical knowledge on materials, by adjusting the research material ratio, changing the reaction conditions, and performing characterization tests and inspections, in order to eventually obtain the required materials [9].…”