Oxidação eletrolítica à plasma do aço AISI 316L com adição de fosfato de cálcio

Abstract

The 316L stainless steel has been widely used as a metallic biomaterial for orthopedic and dental implants due to its excellent mechanical properties and low cost. However, one of the main limitations to its clinical use is the susceptibility to localized corrosion in physiological environments that can result in inflammation, pain and, in the worst case, implant failure. To increase its biocompatibility, the metal can be coated with bioceramic compounds based on calcium phosphate (CaP), in particular, hydroxyapatite, which has a chemical composition similar to the inorganic matrix of bone and a Ca/P molar ratio of 1.67. The objective of this study is to carry out the deposition of calcium phosphate on the metallic substrate of 316L stainless steel using the Plasma Electrolytic Oxidation (PEO) technique, which has the advantages of simplicity, low cost and thermal and chemical stability. The samples were immersed in an electrolyte solution containing calcium acetate, calcium beta glycerophosphate and nitric acid. Then, a potential difference was applied using two configurations: cathodic reaction during times of 90 and 180 seconds and anodic reaction during times of 15 and 20 seconds. The morphology of the coating and its layer thickness were analyzed by Scanning Electron Microscopy (SEM-FEG). Chemical composition and phase were obtained by Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD), respectively. Corrosion behavior was evaluated by Open Circuit Potential (OCP) test. The results showed that the calcium phosphate coatings were successfully deposited on the surface of AISI 316L steel and presented a thick, rough, porous and hydrophilic layer. In addition, the coatings are electrochemically stable and have demonstrated improved corrosion resistance.