Optimization of electrochemical step deposition for bioceramic hydroxyapatite coatings on CoCrMo implants

• Hydroxyapatite was electrodeposited onto CoCrMo alloys to improve biocompability.
• RSM was used to explore the experimental variables for a modified step deposition technique.
• OCP, Ecorr, and low frequency impedance values were used as responses for RSM models.
• Predicted and experimental values were fitted with high accuracy.

CoCrMo metallic implants were coated with a bioceramic hydroxyapatite layer using a modified step electro-deposition at room temperature. Response Surface Methodology (RSM) and Central Composite Design (CCD) were used to model and optimize the step deposition parameters, such as initial potential, scan rate and peak potential. Interactions between step deposition parameters and in vitro corrosion performance of the coatings were modeled by response surface plots. Predicted and experimental values were fitted with high accuracy. The effects of the step deposition parameters were evaluated within the limits of lowest applied potential (− 0.03 to − 1.17 V), scan rate (3.43–116.57 mV/s) and highest applied deposition potential (− 1.08 to − 1.92 V). A 5-level-3-factor experiment plan was used to optimize step deposition parameters. Optimum conditions for the modified step deposition parameters were determined as initial potential of − 0.76 V, peak potential of − 1.67 V and scan rate of 59.33 mV/s.