On the Formation of Porosity in Hydroxyapatite/polyester High-Velocity Oxygen-Fuel Sprayed Coatings and Their Electrochemical Behavior in Simulated Body Fluid

Orthopedic implants play a crucial role in restoring the function and life quality of the population with musculoskeletal disorders. However, implant failure and lack of integration with the surrounding bone tissue, mainly in patients with low bone quality, remain significant challenges in biomedicine. Porous bioactive coatings have emerged as a promising approach to address these issues. This work aims to explore the feasibility of preparing porous hydroxyapatite coatings by high-velocity oxy-fuel spray (HVOF) and, as a first approach, to evaluate the performance of the porous bioactive coatings obtained in simulated body fluid for a possible application in orthopedic surfaces. This paper discusses the use of polyester as a pore-forming agent and the importance of some relevant factors, such as coating fabrication parameters and post-spraying treatments, for producing porosity in the coatings. The results display the formation of different degrees of porosity ranging from 3.8% to 38% depending on the weight fraction of the pore-forming phase employed to prepare the hydroxyapatite coatings. The coatings were evaluated in Hanks balanced solution at body temperature by employing different electrochemical techniques; interestingly, the results suggest different bioactive responses as a function of porosity.