Describes methods for the determination of: - the presence of colourless chromate conversion coatings, - the presence of hexavalent chromium in colourless and coloured coatings on zinc or cadmium or aluminium-zinc (mass fraction of aluminium: 55%, within a range of 54% to 56% mass fraction) and zinc-aluminium (mass fraction of aluminium: 5 %) alloys, - the total chromium content per unit area on zinc and cadmium, - the mass per unit area of both colourless and coloured coatings, - the satisfactory adhesion of chromate conversion coatings, and - the quality of chromate coatings.