Understanding corrosion-assisted cracking of magnesium alloys for bioimplant applications

Magnesium (Mg) alloys possess great potential for their use as temporary implants and devices (such as pins, wires, screws, plates, and stents). Use of Mg alloys as temporary implants will completely avoid the cumbersome procedure of second surgery (which is required when such implants are constructed out of traditional materials such as titanium alloys or stainless steels). However, there are some limitations of Mg as a temporary implant. Firstly, the high corrosion rates of Mg alloys in the physiological environment may lead to loss in mechanical integrity of the implants. Secondly, the simultaneous action of the corrosive human-body-fluid and the mechanical loading can cause sudden and catastrophic fracture due to corrosion-assisted expedited cracking, such as stress corrosion cracking (SCC) and/or corrosion fatigue (CF). SCC and CF of Mg alloy implants are vastly unexplored research areas. This article provides an overview of the experimental results on SCC and CF of different Mg alloys in corrosive environments including simulated body fluid (SBF), and discusses associated fracture mechanisms.