The microstructural corrosion mechanism of a zinc-magnesium-aluminium (ZMA) alloy coated steel (Zn- 2wt%- Al- 2wt% Mg) immersed in 0.17 M NaCl was observed using in-situ time-lapse optical microscopy. The effect of pH on the corrosion mechanisms was assessed by using 0.17 M NaCl adjusted to pH 3, 7, 10 and 13 respectively. The pH of the electrolyte had an influence on the corrosion mechanism of the ZMA alloy. At pH 7 and 10, preferential corrosion of the MgZn₂ lamellae within the eutectic phases was observed followed by subsequent dissolution of Zn-rich phases. A reduction in corrosion was observed using time-lapse microscopy at pH 10, most likely due to the magnesium hydroxide corrosion products being more stable in alkaline conditions, thereby retarding the kinetics of cathodic oxygen reduction and overall rate of corrosion. At pH 3 and 13, the corrosion mechanism appeared to change from localised corrosion, seen at pH 7 and 10, to more generalised corrosion. At pH 3, the MgO corrosion products that seemingly impart benefit to the substrate are dissolved in such acidic conditions. Gravimetric analysis and polarisation experiments were also conducted at the varying pH levels, to compliment the results from time-lapse microscopy.