The effect of ultrasonic liquid metal treatment on the microstructure and the corrosion behaviour of the A356 Al-Si alloy was studied. The microstructures of the Al-Si were observed by means of optical and scanning electron microscopes. The corrosion behaviour was studied electrochemically and by gravimetric method. The results showed that the microstructure was modifi ed from a coarse acicular plate-like form when no ultrasonic vibration was used, to a fi nely dispersed rosette-like form when ultrasonic treatment was employed. The ultrasonically treated samples showed higher resistance to pitting than the untreated sample. The soaking process negatively affected the pitting resistance.

Application of electrochemical impedance spectroscopy on an ultramicroelectrode to study corrosion. Electrochemical and SEM studies on copper in acidic solutions Electrochemical impedance spectroscopy (EIS) and scanning electron microscopy were used to study the corrosion process of copper using an ultramicroelectrode (UME) of area 7,06·10-6 cm2 and a plate 2 cm2 in size. Experiments were carried out in an acidic phthalate buffer in the presence and absence of chloride ions at open circuit potential. The application of EIS made it possible to establish the Faradaic and non-Faradaic parameters of corrosion processes. The experimental ac impedance results were analysed using the model represented by the selected equivalent circuit.