Inhibiting stress corrosion cracking of a prefabricated surface‐defective magnesium alloy thanks to biological organic components

AbstractBiomedical magnesium (Mg) alloys remain a challenge for their mainstream application, because the combination of bio‐mechanical stress and corrosive physiological environment leading to stress corrosion cracking (SCC). It is crucial to avoid the sudden brittle fracture of Mg alloys in vivo for predicting their service duration. However, the key factors, such as surface or physiological environment features, determining the origination or propagation of SCC behavior are still unclear. In the present study, a prefabricated surface defects coating was prepared by the phytic acid (PA, C6H18O24P6) conversion treatment. Four mimicking physiological media were used, ranging from simple to equivalent (Dulbecco's Modified Eagle Medium and Protein [DMEM+Pro]). The results showed that the PA film with numerous micro‐cracks provided limited protective ability in synthetic biological media. A striking finding was determined that although initial high corrosion rate of samples in DMEM+Pro led to an increased SCC nucleation, significant ductile fracture with elongation to failure (14.86%) was observed. Combined with the fracture features, the adsorption or deposition of biological composition into the tunnel of SCC cracks significantly inhibited the hydrogen embrittlement (HE) behavior. These results indicate that preventing the propagation of SCC crack by biological composition, rather than nucleation, plays a key role in avoiding the sudden fracture of Mg alloys. It provides a novel perspective to determine the non‐brittle fracture of Mg alloys for biomedical applications.