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.