Imporved corrosión resistance of 316L SS by cerium-based coating

NADIA CORTES; GONZÁLEZ, MARÍA BELÉN; IVANA LETICIA LEHR

Buenos Aires

Congreso; WCCE11- 11th World Congress of Chemical Engineering; 2023

The aim of the present study was to prepare an adherent and protective cerium-based coating on 316 L stainless steel (316L SS) by a potentiostatic technique. For several years, 316 L SS has been considered an interesting material for medical implants, such as knee or ankle replacements [1]. The main characteristics of this alloy are attractive mechanical properties, reasonable biocompatibility and a low-cost material. Although 316L SS has a protective chromium-enriched oxide film, its corrosion resistance is limited in the presence of Cl- ions due to localized pitting. In the surroundings of an implant, this localized attack releases metal ions that lead to a decrease of biocompatibility, so that the implant may be rejected. Therefore, it is of particular interest to modify the surface of the substrate to prevent corrosion and thus ensure the durability of the implant over a longer period of time. A good strategy for surface modification to create protective coatings is the use of rare earths and cerium in particular. Interest in cerium-based coatings has increased in recent years due to their low toxicity, biocompatibility, and improved corrosion protection performance [2]. The protective mechanism of cerium species is the formation of highly insoluble cerium oxides and hydroxides specifically in the active cathodic zones of the substrate. It has also been investigated that the combination of oxidants with cerium salt improves the corrosion resistance of the substrates.Materials and methodsThe electrodes were treated in an electrolyte solution containing cerium nitrate hexahydrate Ce(NO3)3.6H2O (15-50 mM) in an atmosphere saturated with purified nitrogen gas. The temperature used was 50 °C. The concentrations of hydrogen peroxide (H2O2) were varied between 1-49 mM. Electrochemical studies were performed using an Autolab/PGSTAT 128N potentiostat/galvanostat. Optimum experimental conditions were determined to obtain films with improved corrosion protection properties in simulated physiological solution. The influence of the composition of the electrosynthesis solution was analyzed on both film formation and corrosion protection performance in simulated physiological solution (Ringer's solution).ResultsAdherent and uniform golden yellow films were obtained on 316L SS in solutions containing cerium nitrate and H2O2. The best adherent and most homogeneous coatings were obtained by potentiostatic polarization at - 1.00 V at 50 °C for 30 minutes. Tafel polarization curves were recorded to confirm the anticorrosive performance of the coatings. The results indicate that the coating obtained with 30 mM Ce(NO3)3 and 49 mM H2O2 causes an anodic shift in the corrosion potential (Ecorr) and a decrease in the corrosion current density by an order of magnitude compared to the uncoated alloy.ConclusionsFrom these preliminary results, it can be concluded that adherent and uniform coatings of cerium salts have been deposited on 316L SS. The anticorrosive performance of the obtained coatings showed corrosion protection for the substrate in Ringer's solution. In this way, the material would be a promising proposal for corrosion protection of AI 316 L implants.