CORROSION BEHAVIOUR OF DISSIMILAR FRICTION STIR WELDED AA2017 AND AA7075 IN SIMULATED ATMOSPHERIC CORROSION ENVIRONMENT

• Main Author: Hasbi Zamrudi, Firdausi
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/67949
• Institution: Institut Teknologi Bandung

Friction stir welding is a promising joining technique that offers safety, reproducibility, lower energy consumption, without shielding gas and consumables, and does not involve a solidifica-tion process. Nevertheless, the atmospheric corrosion behavior of dissimilar friction stir weld-ments in each zone has not been widely studied. In this research, the electrochemical properties of the parent metal, thermo-mechanical affected zone, and weld zone in AA2017/AA7075 dissimilar friction stir welded are observed using open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy. We also conducted 120 days urban atmospheric corrosion test and characterized the result by visual photography, x-ray diffraction, fourier transform infra red spectroscopy, and scanning electron microscope equipped with energy dispersive x-ray. As a result, electrochemical testing data showed that corrosion progressed more rapidly in the stir zone and thermo-mechanical affected zone compared with the parent metal. The highest corrosion rate 17.66 mpy achieved by specimen A3 (1250 RPM 80 mm/min) in 3.5% Na2SO4 + 3.5% NaCl. While the lowest corrosion rate 0.06 mpy was obtained by specimen B1 (800 RPM 100 mm/min) in 3.5% NaCl electrolyte. Moreover, the exposed sample stir zone showed micro galvanic and intergranular corrosion. This weldments corrosion susceptibility is mainly caused by microgalvanic interactions between the AA2017-rich zones and AA7075-rich zones.