Electrodeposition of biphasic calcium phosphate coatings with improved dissolution properties

Highlights: • Biphasic calcium phosphate coatings (HAP/β-TCP) are electrodeposited on Ti6Al4V. • H₂O₂ addition to the electrolyte modifies the composition and the morphology of the coatings. • The bioactivity of the coatings is assessed in physiological solution from 1 to 28 days. • The biphasic coatings protect Ti6Al4V from the corrosion reactions in physiological solution. -- Abstract: Biphasic calcium phosphate coatings (hydroxyapatite/β-tricalcium phosphate) on titanium substrate (Ti6Al4V) are synthetized by pulsed current electrodeposition coupled to a thermal treatment under controlled atmosphere. The experimental conditions of the process such as the hydrogen peroxide amount and the treatment temperature are optimized in order to obtain different coatings compositions. The physico-chemical and structural characterizations of the coatings are carried out respectively by scanning electron microscopy associated with energy dispersive X-ray spectroscopy (SEM-EDXS) and X-ray diffraction (XRD). The in vitro dissolution-precipitation properties of the coated substrates are investigated by immersions into Dulbecco's Modified Eagle Medium (DMEM) from 1 to 28 days. The calcium and phosphorus concentrations variations in the biological liquid are assessed by Induced Coupled Plasma - Atomic Emission Spectroscopy (ICP-AES) for each immersion time. Furthermore, the corrosion behavior of the coated substrates are investigated using potentiodynamic polarization tests in DMEM and in Ringer's solution. The results show that this innovative process is suitable to synthesize two coatings composed respectively of HAP (37%)/β-TCP (63%) and HAP (62%)/β-TCP (38%) with different morphologies. On the other hand, the in vitro studies reveal that the coatings composition greatly influences their behavior in physiological medium, i.e. their dissolution-precipitation and their corrosion protection properties.