Contents lists available at ScienceDirect Surface & Coatings Technology journal homepage: www.elsevier.com/locate/surfcoat Effect of electrodeposition parameters and substrate on morphology of Si- HA coating Neda Aboudzadeh a , Changiz Dehghanian a, ⁎ , Mohammad Ali Shokrgozar b a Tehran, Iran b National Cell Bank of Iran, Pasteur Institute of Iran, Tehran, Iran ARTICLE INFO Keywords: Mg alloy Si-HA coating Morphology Electrodeposition ABSTRACT In this study, a Si-HA coating was deposited on Mg-5Zn-0.3Ca alloy substrate by pulse electrodeposition. The effect of varying electrodeposition parameters like current density (20, 40, 60 mA/Cm -2 ), duty cycle (0.1, 0.2), pH (4, 5, 6) and temperature (25, 85, 100 ̊ C) on the composition and morphology of coating were investigated. A homogenous nano-needle morphology of Si-HA coating was chosen as optimum coating. Regarding to results obtain from SEM and XRD, in low current density of 20 mA/cm -2 a coarse and non-uniform coating was de- posited and in high current density of 60 mA/cm 2- , high amounts of hydrogen gas at interface was produced and a non-uniform coating was formatted once more. At middle current density of 40 mA/cm -2 , nano-needle like coating could be deposited. According to results, an increase in duty cycle from 0.1 to 0.2 increased the t on and the pH of electrolyte vicinity of cathode and cause calcium phosphate of DCPD deposited along with HA on surface and morphology of coating was also changed from needle like to think plate like. The results also indicated coatings had micro size sheets and agglomerated morphology in 25 ̊ C and 100 ̊ C, respectively, whereas coating had nano-sized needle- like blades approximately 100–200 nm in length and < 100 nm in thickness in 85 ̊ C. the pH less or > 5 for electrolyte (4 and 6) made the plate like morphology for coating. Moreover, the results indicated that the selection of composited Mg alloy with nano-HA as a substrate caused the deposition of Si-HA coatings on it to be more homogenous with better interface in comparison to that of Mg alloy selection as a substrate. 1. Introduction Improving the corrosion resistance and biocompatibility of Mg alloy is significantly important for its application as orthopedic implants [1–3]. In response to this concern, many research focused on bioactive coating for Mg and its alloys [4–6]. Improving corrosion rate and in- creasing bioactivity are two main advantages of these coatings for metal implant [7,8]. Bioactive coatings such as hydroxyapatite (HA) [4–6,9], silicon-containing coating [10,11], strontium phosphate (SreP) coating [12,13], Composite magnesium phosphate [8] was used for Mg and Mg alloys. New bioactive multilayer coatings such as multilayer SiC-SiC nanowire-Si doped HA coating [14], pyrolytic carbon-SiC-fluoridated HA-HA multilayered coating [15], carbon/SiC nanowire/Na-doped carbonated HA multilayer coating [16] were also introduced for this substance. These bioactive coatings with well masking provide stability at the initial stages after implantation and accelerate tissue regenera- tion. Dehghanian et al. [1] have found that employing Si substituted HA coating on Mg alloy promote deterioration time of implant and match it to the healing time of bone. Reviewing of these coatings show that the most interest is on HA base coatings. HA as main inorganic phase of bone [17] with outstanding biocomapatibility, bioactivity and osteo- conductivity is almost the first candidate for researchers. However, natural apatite is not stoichiometric HA and rather it contains ions likes Mg 2+ , Zn 2+ , Sr 2+ and Pb +2 instead of Ca 2+ ; or CO 3 2- , SiO 4 3- in place of PO 4 3- , as well as F - or Cl - ions instead of OH – , which progress its osseointegration [12,18]. It was reported, the substitution of PO 4 3- by SiO 4 3- increased the corrosion resistance and improved the cell pro- liferation [1]. It was improved that morphology and crystal structures of bioactive coatings in same of composition directly affect on its biocompatibility and osteoconductivity [19,20]. Natural apatite in bone has needle like morphology with 2–3 nm thickness and tens of nanometers in length and width [21]. Needle like morphology in comparison to the plate like morphology had higher effective surface which accelerated the pre- cipitation of calcium and phosphor on surface in SBF solution and ef- fectively control deterioration of implant and indorses the bone tissue https://doi.org/10.1016/j.surfcoat.2019.07.016 Received 28 April 2019; Received in revised form 1 July 2019; Accepted 7 July 2019 ⁎ Corresponding author at: University of Tehran, Iran. E-mail address: cdehghan@ut.ac.ir (C. Dehghanian). Surface & Coatings Technology 375 (2019) 341–351 Available online 19 July 2019 0257-8972/ © 2019 Elsevier B.V. All rights reserved. T