GB/T 30790.4-2014 specifies the technical requirements for surface types and surface preparation in protective coatings systems for steel structures. The standard covers a variety of surface types of carbon steel or low alloy steel, including non-coated surfaces, thermal spray metal surfaces, hot-dip galvanized surfaces, Eletroplating zinc surfaces, powder galvanized surfaces, pre-coated undercoated surfaces and Miscellaneous painted surfaces. At the same time, a variety of surface preparation methods and grades are defined, such as jet cleaning, water jet cleaning, flame cleaning, etc., and the surface roughness requirements after treatment are clarified. The standard provides detailed technical guidance for the surface preparation of steel structures, ensuring the adhesion and durability of coating systems, and is suitable for the design, construction and acceptance of protective coatings systems.