Numerical modeling of galvanic corrosion behaviour into simulated body fluid of hybrid joint

The possibility of using magnesium (Mg) alloys in biomedical field gives a lot of advantages. Their mechanical properties are more similar to the bone tissue than conventional metals and make the Mg a promising material for bio-engineering applications. The major restriction of Mg and its alloys is the degradation in organic human environment. Nevertheless, if implants or their components do not have to be permanent, there is the possibility to exploit the benefits provided by use of Mg. The anodic behaviour of Mg is enhanced when it is coupled with a nobler metal like titanium (Ti). The idea to couple these different materials to create a hybrid joint is proposed in this paper. This solution allows to have a wide range of improvements for the patient, for instance a quicker tissue regeneration due to release of Mg ions and a less pain related to the implant development due to degradation of non-permanent screws. The Mg corrosion rate control through the use of proper coatings on the metal surface is essential in this scenario. The knowledge of the weight loss value of the electrolytic cell is necessary to design a right coating. For this purpose, a macro galvanic corrosion (GC) numerical model of a joint composed by Ti6Al4V and two different Mg alloys, such as AZ31 and AZ91, is proposed in this study and simulations are carried out by using a FEM software. In this work the corrosion phenomenon of the Mg alloys was investigated in order to increase the opportunities of using hybrid joints in biomedical field exploiting their benefits through appropriate precautions, mostly related to coatings which have to be properly designed.