ISO 12944-4:2017 covers the following types of surfaces of steel structures consisting of carbon or low-alloy steel, and their preparation: - uncoated surfaces; - surfaces thermally sprayed with zinc, aluminium or their alloys; - hot-dip-galvanized surfaces; - zinc-electroplated surfaces; - sherardized surfaces; - surfaces painted with prefabrication primer; - other painted surfaces. ISO 12944-4:2017 defines a number of surface preparation grades but does not specify any requirements for the condition of the substrate prior to surface preparation. Highly polished surfaces and work-hardened surfaces are not covered by ISO 12944-4:2017.