The effect of testing conditions on stress corrosion cracking of biodegradable magnesium alloy ZK60

Abstract

The effect of the chemical composition, temperature, circulation and pH of the simulated body fluid (SBF) on the corrosion and stress corrosion cracking (SCC) susceptibility of the alloy ZK60 was studied through the immersion and slow-strain rate tensile (SSRT) testing respectively. It is found that both the corrosion and SCC susceptibility of the alloy is significantly affected by chemical composition and adjustment of pH level of SBF, while the temperature and circulation of the SBF exert a minor effect on these characteristics. The pH adjustment of 0.9 % NaCl solution to 7 ± 0.2 was done automatically and continuously during the SSRT testing by refreshment of the SBF. The control over pH decreased the corrosion rate and increased the SCC susceptibility of the ZK60 alloy. It is established that, in the considered SBFs (0.9 % NaCl, Ringer’s and Hank’s solutions), the alloy ZK60 possesses the highest SCC susceptibility and the least corrosion rate in Hank’s solution, while in Ringer’s solution, the SCC susceptibility and corrosion resistance are lowest. It is concluded that the experimental factors considered in the present study have to be accounted for in the reliable assessment of the corrosion and SCC resistance of the biomedical Mg alloys.