Its low density, high strength and corrosion resistance make aluminium and its alloys the material of choice for many application in, among others, the automobile, aircraft/aero space and packaging industry. Metallography is used in quality control for grain size, determination, evaluation of phases, impurities and mechanical defects. Pure aluminium is very susceptible to deformation and therefore grinding should not be carried out with coarse grits. A very thorough final polishing with silicon dioxide suspension is necessary to ensure that embedded diamond particles are completely removed from the sample surface. Aluminium cast alloys are polished relatively easily. For grain size evaluation anodizing with Barker’s reagent is particularly suited as it results in a better contrast than chemical etching. Different phases in cast alloys can either be identified by their characteristic color or by etching with specific solutions that attack certain phases preferentially.