Corrosion characteristics of sintered heterogeneous materials composed of iron and iron oxides

In a coronary angioplasty or orthopaedic surgery, metallic implants are often used to provide mechanical support to the healing tissues. In some situations, this support is really needed only temporarily. After tissue recovery, the implant no longer provides any benefits and can trigger adverse reactions. An optimal solution might be the short-term implants which are able to decompose in situ and can be readily excreted from the body. Iron-based materials are promising candidates for application in biodegradable devices. For the successful application, the ability to control the material’s corrosion rate is important. In this contribution, the corrosion of iron-iron oxide composites is investigated. In order to obtain such materials, iron-oxide granules were incompletely reduced, compacted and sintered. Materials consisting of a pure iron and iron oxides were obtained. Specimens from as-sintered materials and materials reduced once again after sintering were prepared. Potentiodynamic polarization testing in Hanks’ solution indicated that specimens underwent a galvanic corrosion, where the release of ferrous ions from iron surfaces represents the anodic reaction and the oxygen reduction on surfaces of both iron and iron oxides represents the cathodic reaction. Changes in the content of oxides resulted in anticipated shifts in corrosion potential and apparent corrosion current density.