This study focuses on the stress corrosion behavior of the Mg-Zn-Zr alloy system in extruded condition (tubes). The binary alloys Mg-Zn and Mg-Zr are compared to the ternary alloy system regarding microstructure, hardness, bending strength and corrosion behavior. C-ring tests in Ringer solution are used to evaluate the stress corrosion properties. POM polymer, being corrosion resistant and neutral to the Mg-corrosion, was chosen to build up the test set-up for the C-ring tests. Bending tests have been done to determine the elastic-plastic region of the samples - before starting the C-ring experiments. Twinning as a result of deformation increases the corrosion rate and is most prominent at the Mg-Zr alloy. Signs of pitting corrosion to different extents have been found in all alloys investigated. The Mg-Zn alloy corrodes the most within this alloy group. Plastic deformation is increasing the corrosion, however, signs of stress corrosion cracking could not be found.