The electrochemical behaviour of magnesium and different wrought alloys, AZ31, AE42, LAE442, and ZEK100, with and without heat treatment, was examined with the Mini-cell System by linear sweep voltammetry in 0.5wt.% and 3.5wt.% NaCl solution. The corrosion damage was characterised by scanning electron microscopy. Magnesium and the different alloys exhibited strong differences in their electrochemical behaviour. Alloying with aluminium increases the corrosion resistance. However, the magnitude of this improvement depends on uniform sizes and distributions of the Al-rich phases. Similarly, the influence of the heat treatment on the corrosion resistance depends on the produced distribution of precipitates. Magnesium and its alloys corrode quite rapidly in comparison with other metals, and there is pronounced hydrogen development. The latter increased with increasing NaCl concentration, although no great differences in the corrosion in both concentrations were observed, except on pure magnesium and ZEK100.