Corrosion analysis of hydroxyapatite coated magnesium in simulated body fluid (SBF), phosphate buffered saline (PBS), and Ringer's solution

Magnesium, Mg is well known as a degradable biomaterials and the degradability is governed by corrosion process.. In order for Mg to be bioactive, hydroxyapatite, HA coating seems to be the best candidate for Mg. The main objective of the current work is to assess the corrosion behaviour of HA coated Mg inside different corrosion media (SBF, PBS, and Ringers). The coated samples were prepared via two steps chemical conversion coating, which is the primary step were by phosphating and followed by secondary alkaline treatment. Corrosion analyses were conducted by using potentiodynamic polarization and the effect of different corrosion media is evaluated from microstructural and phase analysis perspective. It is suggested that the corrosion properties of HA coated Mg is strongly influenced by ionic concentrations of the corrosion testing solutions. It is found that the corrosiveness of the solution media (from less to the most corrosive) is given by PBS < SBF < Ringers. The Cl- concentrations strongly affect the corrosion rate inside the tested solutions. However, presence of other ions inside the tested solutions such as HCO3-, HPO42-, SO42- helps inhibits the attack of aggressive Cl- ions.