RESISTANCE TO ELECTROCHEMICAL CORROSION OF THE EXTRUDED MAGNESIUM ALLOY AZ80 IN NaCl SOLUTIONS ODPORNOST EKSTRUDIRANE MAGNEZIJEVE ZLITINE AZ80 PROTI ELEKTROKEMIJSKI KOROZIJI V RAZTOPINI NaCl

The purpose of this study was to evaluate the electrochemical corrosion resistance of the extruded magnesium alloy AZ80 in NaCl solutions. The resistance to electrochemical corrosion was evaluated on the grounds of registered anodic polarisation curves. Potentiodynamic tests were performed in solution with a concentration of 0.01–2.00 M NaCl. In addition, immersion tests were performed, and they allowed us to determine the corrosion rate. Scanning electron microscopy was applied to observe the microstructure after the immersion tests (after removing the corrosion products). Phenomena that happen on the surface of the alloy were evaluated with the application of electrochemical impedance spectroscopy. The tests enabled us to determine the impedance spectra of the system and the data obtained during the measurement was matched to the equivalent system. An optical profilometer was used for the measurement of the geometrical features of the surface of the alloy. The results of the performed tests prove explicitly the deterioration of the corrosion characteristics of the alloy with an increase in the molar concentration of the NaCl solution. A decrease of the corrosion potential and the polarisation resistance was observed, as well as an increase of the corrosion current density. It was proved that irrespective of the concentration, pitting corrosion can be found on the surface of the alloy. The potential to use the extruded magnesium alloy AZ80 in the aircraft and automotive industries is connected with the necessity to apply protective layers on elements made from the tested alloy.