Effect of acid–base reaction on the electrophoretic deposition of hydroxyapatite nanostructured coatings in isopropanol

Triethanolamine (TEA) was added along with acetic acid (AA) to enhance the stability of hydroxyapatite (HA) nanoparticles in isopropanol. H⁺TEA ions generated by AA and TEA reaction were adsorbed on particles and increased their zeta potential. Zeta potential increased to the maximum value at optimum concentration of AA (AA*) and then decreased with its further addition. Kinetics of EPD increased with AA addition into the TEA containing suspensions. Detachment of particles from deposits into the suspensions was the fastest at AA* due to the highest electrochemical potential difference at the interface. Sticking parameter (f factor) was the minimum at AA*. Corrosion rate of substrate considerably decreased in simulated body fluid (SBF) at 37 °C as the HA coating was applied on it. Apatite layer grew on the coating after its soaking in SBF at 37 °C for 1 week. (paper)