Investigating corrosion behaviors of anodized metallic implants by electrochemical analysis

Abstract

Biomaterials are used in implantations inside the human body and have been a reliable method for a long time but not without detrimental effects. Although biomaterial manufacturing companies claim a longer service life for implants, it has been found that after a few years of implantation, a number of patients have complained about severe pain around the implantation areas attributed to the corrosion of implants. A number of research studies are undergoing to understand and reduce this corrosion. Anodization is a method performed in an electrolyte solution to reduce corrosion. Subsequent tests have been performed to recognize the impacts of anodized biomaterials, which includes immersing them into various solutions. The purpose of this research was to carry out a long-term investigation of the corrosive behavior of both anodized and non-anodized biomaterials under controlled conditions. The titanium alloy Ti6Al4V was anodized in 0.4 M phosphoric acid (PHOA) and 0.5 M oxalic acid (OXA), and the magnesium alloy MgAZ31B was anodized in 0.4 M PHOA and 1 N potassium hydroxide (KOH) by applying 20 V DC potential. Prolonged investigations were performed by immersing them in 3% sodium chloride (NaCl), phosphate buffered saline (PBS), and deionized (DI) water solutions and measuring the corrosion rate and pattern by electrochemical analysis. Anodized titanium (Ti) and magnesium (Mg) alloys have been found to be more corrosion resistive than their non-anodized alloys. Maximum corrosion rates (CRs) of 3.0430 mpy and 0.78447 mpy were found for non-anodized and anodized Ti6Al4V, respectively, after immersion in 3% NaCl solution for 1,080 hours. Maximum CRs of 1640.02 mpy and 868.63 mpy were found for nonanodized and anodized MgAZ31B, respectively, after immersion in 3% NaCl solution for 12 hours. It was observed that anodization increases the natural oxide layer on the material surface, which decreases the corrosion rate and prolongs the life of the biomaterial.