Effect of chemical composition on hydrophobicity and zeta potential of plasma sprayed HA/CaO–P2O5 glass coatings

Multilayered plasma sprayed coatings on the surface of Ti–6Al–4 V alloys have been prepared, which were composed of an underlayer of HA and a surface layer of a CaO–P2O5 glass–HA composite, with 2 or 4 wt% of glass. Contact angle and surface tension variation with time, for both water and a protein solution, were determined by the sessile and pendent drop methods respectively using the ADSA-P software. Wettability studies showed that hydrophobicity of the coatings increase with the glass addition. The work of adhesion of albumin was also altered in a controlled manner by the addition of the CaO–P2O5 glass, being lower on the composite coatings than on HA. Zeta potential (ZP) results showed that composite coatings presented a higher net negative charge than HA coatings and that ZP values were also influenced by the content of the glass. This study demonstrated that the surface properties of those coatings may be modified by the addition of CaO–P2O5 glass.