CORROSIVE PROPERTIES DISTRIBUTION IN AW-7020 ALLOY JOINTS WELDED BY FSW

The results of corrosion properties research of aluminum alloy AW 7020 (AlZn5Mg1) welded by Friction Stir Welding were presented. In the article the parameters for friction stir welding of sheets made of AlZn5Mg1 (7020) alloy were presented. Corrosion tests were performed on the surface of the FSW joined sheets depending on the distance from the centre of the weld. EIS measurement was performed in three-electrode system in an artificial seawater (3.5% NaCl). Impedance studies were carried out at the corrosion potential. Changed voltage signal amplitude in the range ± 10 mV and frequency range of changes was as follows: 100 kHz - 0.1 Hz. Atlas 0531 EU & IA potentiostat was used for studies. Model in the form of an electrical equivalent circuit replacement was chosen for the test object. The results of electrochemical impedance spectroscopy are presented graphically in the Nyquist charts matched with the theoretical curve to them and in the form of parameters characterizing the corrosion process. Obtained results were statistically analysed. Better resistance to electrochemical corrosion was found for the native material then joint welded by FSW of 7020 aluminum alloy. Worse corrosion properties were observed in the advancing side of the weld than in the retreating side of the weld. Original value are received results of the corrosion properties distribution of FSW welded AW-7020 aluminium alloy.