Influence of ceramic coating on corrosion properties of sintered iron materials

Biomaterials have become an essential part of modern medicine as components of orthopedic implants. Metals such as iron or magnesium are most used for this purpose. By applying different coatings to metals, it is possible to change, improve and adjust the properties of metallic materials to the desired applications. Hydroxyapatite is often used as a bioactive coating in the field of biomaterials mainly due to good biocompatibility and osteoconductivity. The paper is focused on the study of the degradation properties of iron-based biomaterials. The iron samples were prepared from carbonyl iron powder by cold pressing into pellets followed by sintering in a reductive atmosphere for 1 hour. A bioceramic hydroxyapatite (HAp) coating was applied to the surface of the sintered iron samples by electrochemical deposition for 15, 30, and 50 minutes. The corrosion properties of samples were studied using an anodic polarization method in Hanks´s solution. Electrochemical impedance spectroscopy measurements were performed after immersing the samples for 60 minutes in Hanks's solution. Based on dynamic tests, a shift to a more negative value of the potential was observed for the sample with a longer time of HAp deposition, which indicates a stronger restriction for the transport of dissolved oxygen to the iron surface. Compared to the iron sample without the ceramic coating, a shift to a positive efficiency value was observed for the HAp coated samples.