**2.4 In vitro degradation tests**

Electro-chemical measurements and immersion tests were performed in a Hank's simulated body fluid to evaluate the in-vitro degradation properties. The chemical composite of Hank's simulated body was listed in table 2.The pH value of Hank's solution was adjusted with HCl and NaOH to 7.2~7.4, to avoid precipitation or formation of sediments in the solution. Its temperature was controlled around 37 ± 0.5 0C, which is equal to the human body normal temperature. Pure Mg (>99.99%) was also tested as a contrast.
