Corrosion behaviour of magnesium and WE43 magnesium alloy in 1 M NaCl aqueous solution was studied by potentiodynamic polarisation and advanced acoustic emission (AE) analyses. The AE parameters suitable for the monitoring of corrosion in magnesium were shown to be the AE counts, rise time, and duration. Moreover, the mechanisms of corrosion in these materials, i.e. the ion exchange, rupture of the protective film, and the pitting corrosion were identified and their evolution was followed by the novel Adaptive sequential k-means clustering technique. The presented methods can be also suitable for monitoring of different materials and for industrial applications.