Sinusoidal Modulated Direct Current for Controlling Hydroxyapatite Crystal Growth on SS 316L via Electrochemical Deposition
Alivia Nurul Avivin (a,b), Prabowo Puranto (b*), Anawati Anawati (a*)

(a) Departement of Physics, Faculty of Mathematics and Natural Sciences, Universitas of Indonesia, Depok, 16424, Indonesia
(E-mail: alivia.nurul[at]ui.ac.id, and anawati[at]sci.ui.ac.id)
(b) Research Center for Composite and Biomaterials, National Research and Innovation Agency (BRIN), South Tangerang, 15314, Indonesia
(E-mail: prabowo.puranto[at]brin.go.id)

Abstract

Abstract
Hydroxyapatite (HA) coatings were electrochemically synthesized on Stainless Steel 316L substrates using a unipolar sinusoidal modulated direct current (SMDC) at equivalent potentials of 2, 2.5, and 3 V, while conventional direct current (DC) deposition served as the control. The sinusoidal modulation was designed to maintain deposition continuity while mitigating hydrogen evolution effects commonly associated with porosity and structural defects in conventional electrodeposition. Under the modulated electrical configuration, the electrochemical interface underwent dynamic ionic redistribution and transient potential stabilization, promoting a more coherent nucleation-growth pathway. Morphological evaluation revealed a transformation from porous granular structures toward densely interwoven acicular architectures with increasing potential. Compared with conventional DC deposition, SMDC produced coatings with enhanced structural compactness, refined morphological homogeneity, and reduced defect formation. X-ray diffraction analyses confirmed crystalline hydroxyapatite formation and intensified crystallographic development under modulated conditions, particularly at the relatively low potential of 2.5 V. Furthermore, SMDC significantly amplified deposition kinetics, producing coating thicknesses of approximately 8-24 &#956-m, exceeding those obtained via conventional DC deposition (6-11 &#956-m). Electrochemical characterization further demonstrated the most effective corrosion protection at 2.5 V SMDC. Thus, unipolar SMDC represents an effective electrochemical strategy for governing HA crystal evolution and improving orthopedic implant surface protection.

Keywords: Unipolar SMDC, Hydroxyapatite, Coating, Methods, Electrochemical Deposition.

Topic: Material Physics