EMPIRICAL MODEL TO PREDICT THE HYDROXYAPATITE THICKNESS ON THE SURFACE OF 316L STAINLESS STEEL BY THE DIP COATING METHOD

The surface of 316L stainless steel can be coated with hydroxyapatite to overcome its disadvantages as a medical implant, such as low biocompatibility and the release of toxic metal ions in the body after implantation. The coating thickness is one of the important parameters in the coating process. The use of a model to predict the coating thickness is needed to achieve a standard thickness of the coating. This research aim is to determine the empirical model of the hydroxyapatite coating thickness on the surface of 316L stainless steel by the dip coating method. The HA slurry was made by mixing HA powder, polyethylene glycol, and distilled watere using a magnetic stirrer. The 316L stainless steel substrate were dipped into the slurry and then followed by a drying and sintering process. The empirical model of the HA coating thickness on the surface of the 316L stainless steel in this research is y = 406 -29.5 A -16 B -0.588 C + 1.6 AB + 0.0359 AC + 0.0328 BC -0.00185 ABC with an R2 value of 98.17 %. The empirical model which consists of only significant parameters is y =-101.3 + 1.861 A + 11.774 B. The significant parameters which affect the coating thickness are the amount of HA and the immersion time. The longer the immersion time and the higher amount of HA used, the thicker the coating will be achieved.