Available online www.jocpr.com Journal of Chemical and Pharmaceutical Research, 2015, 7(4):1018-1023 Research Article ISSN : 0975-7384 CODEN(USA) : JCPRC5 1018 Effect of number of coatings on structure, mechanical properties and corrosion behaviour of HA coating on 316L stainless steel Deepak Narang and Uma Batra Department of Materials and Metallurgical Engineering, PEC University of Technology, Chandigarh, India _____________________________________________________________________________________________ ABSTRACT In this study, hydroxyapatite coatings were deposited on AISI 316L stainless steel using sol–gel dip coating method. The three coatings were developed by subjecting the substrate to three; four and five times dip in the sol. The surface morphology and elemental analysis of coatings were studied using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. The porosity in coating was determined using inverted metallurgical optical microscope (Zeiss Axiovert 200 MAT) fitted with imaging software (Dexel, version 1.3.4). The surface roughness was determined using surface testing machine (Surftest, Mitutoyo, model SJ-400) for a cut-off of 0.8 mm. The micro hardness test on coated samples was conducted using a Vicker’s micro hardness tester (model HV-1000 V, Huayin). The adhesion strength of the coatings was calculated using Hertz equation. The coating developed by four times dip demonstrated the minimum surface roughness; maximum micro hardness and adhesion strength. In order to investigate the corrosion behavior of uncoated and hydroxyapatite coated 316L stainless steel, electrochemical potentiodynamic polarization tests were performed in physiological solutions at 37±1 ◦ C. The coating developed by exposing substrate for four times dip in sol. offered a better corrosion protection of the substrate compared to coatings developed by exposing for three or five times dip in sol. Keywords: 316L stainless steel, dip coating, hydroxyapatite, sol-gel, surface roughness, linear polarization _____________________________________________________________________________________________ INTRODUCTION Metals, polymers, ceramics and composites are being immensely employed to replace bones in surgery of the damaged parts. Among various materials available in the market, metallic biomaterials like titanium alloys and stainless steels are widely used for the implant surgery applications due to their good corrosion resistance and mechanical properties. There are many reports on improvement by employing hydroxyapatite (HA) coatings on the surface of the metallic implants [1-4]. Hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) is one of the most prominent biocompatible ceramic materials which promotes osseointegeration of implant materials to surrounding tissue due to its similar composition and structure to the human body [5-8]. A survey of literature reveals that there are many techniques employed for synthesis of HA coatings on the surface of metallic biomaterials. These include plasma spraying [9-11], sputtering [12,13], electrophoretic deposition [14-17] and sol-gel [19-24]. Among all the above methods sol-gel technique plays a vital role due to many advantages such as: (a) synthesis of thin or thick film with a high porosity area which improves the efficiency of sensor (b) modification in composition with uniformly dispersed dopants (c) easy control on film thickness (d) excellent homogeneity (e) ability to coat large area and complex shape (f) equipment’s can be assembled at low cost (g) low temperature in processing. Generally there are three methods that are used in the sol-gel technique. These are spin coating, dip coating and spray coating. In this