Low interfacial pH discloses the favorable biodegradability of several Mg alloys

Abstract

Low interfacial pH (7.5–8.0) and corrosion rate were found for several Mg alloys (CP-Mg, UHP-Mg, Mg-0.15 wt%Ca, Mg-4 wt%Ag) in Ca2+-containing Hanks’ Balanced Salt Solution (HBSS, = 7.4) at 37 °C under hydrodynamic condition. Low interfacial pH and corrosion rate originated from the facilitated formation of the protective calcium-phosphate-rich precipitates at 37 °C. This study indicates that Mg degradation in a quasi-physiological environment causes only slight alkalization (pH < 8.0), as opposed to the high local and bulk pH (ca. 10.4) characteristic for Mg in NaCl electrolyte. It is also stressed that no synthetic pH buffers should be added to constantly supplied Ca2+-containing HBSS.