The Effects of HAc Etching on the Degradation Behavior of Mg-5Gd

Abstract

The effects of different acetic acid (HAc) etching procedures were investigated using Mg-5Gd samples in as-extruded and T4 conditions in order to achieve defined surfaces and homogenous degradation behavior. Samples were dipped into HAc solution with five different concentrations for three durations. In total, fifteen different etching conditions were tested with regard to the degradation resistance in physiological solution. The cell culture medium consisted of Dulbecco's Modified Eagle Medium (DMEM), Glutamax, 10 Vol.-% fetal bovine serum (FBS) and 1 Vol.-% Streptomycin/Penicillin solution. A screening test was performed to select the etching combinations with the lowest initial mean degradation depth. The most promising etching procedures were chosen for further long term degradation tests lasting up to 30 days in cell culture medium. The surfaces of the etched samples and for selected samples after degradation were characterized by interferometry, OM, SEM, and XRD to correlate the influence of morphology, roughness and microstructure on the degradation rate. Etching with 250 g/L HAc and 150 s leads to the most uniform degradation with low degradation rate compared to non-etched Mg-5Gd.