Multi-Method Approach to Assess the Corrosion Behavior of a Coated WE43 Mg Alloy

Developing appropriate and functional coatings for Mg alloys, such as WE43, in view of controlling the degradation rate in biodegradable applications, requires a realistic understanding of the corrosion processes. While conventional methods, such as electrochemical measurements, can already give a good estimation about the protectiveness of coatings, immersion tests are also required to simulate a more realistic corrosion scenario (i.e., open-circuit dissolution as a function of time). In the current study, immersion tests at pH 5 were performed in a solution composed of the inorganic Dulbecco's Modified Eagle's Medium constituents. For four different types of coatings on WE43, a combined experimental approach was introduced that compares the corrosion rates obtained by the different methods. The strengths and drawbacks of the methods, such as hydrogen evolution and ion release measurements, mass loss, and electrochemical tests, will be discussed. The different monitoring methods all have their advantages; thus, for a profound examination, multiple methods should be used in a complementary manner. For the evaluation of the corrosion protection ability of coated samples, the hydrogen evolution measurements may offer the most advantages.