The use of bioresorbable materials made of magnesium alloys has increased considerably over the past few years due to their mechanical, antibacterial, and osseointegrative properties. However, there are some issues associated with the use of these alloys, which can be subjected to extensive and rapid corrosion phenomena. The biological environment is aggressive and contains chlorides, thus causing extensive corrosion phenomena and rapid dissolution of the metal without complete tissue healing. Corrosion products such as hydroxides and hydrogen bubbles can, in addition, accumulate in biological tissues and exert detrimental effects.

This study investigates the effect of composite coatings consisting of geopolymer and chitosan on the corrosion behaviour of AZ31 alloy substrates. Given its microporous nature, the coating does not exert a complete barrier effect (which would block corrosive phenomena and thus bioresorption) but attempts to modulate the corrosion rate.

The coatings were produced by mean of dip-coating deposition and were studied morphologically and chemically using SEM/EDXS measurements. Samples were immersed in saline solution, phosphate buffered saline solution (PBS) and Hanks' Balanced Salt Solution (HBSS), respectively, to simulate the biological environment.

Hydrogen evolution measurements were initially carried out at different time steps to assess corrosion behaviours. Subsequently, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements were also performed to study the effect exerted by the coating.