Traditional coatings fall into several categories, with fluorocarbon coatings being the highest grade-offering corrosion resistance for nearly 20 years. These materials are typically distributed from steel mills in the form of coils. The "color-coated steel sandwich panels" frequently seen in construction consist of a core filler material sandwiched between two layers of color-coated steel sheets, with a total thickness ranging from approximately 50 mm to 100 mm. The color-coated steel sheets themselves-steel panels finished with an organic coating-are only 0.15 mm to 1.5 mm thick. Common thicknesses for these sheets include 0.4 mm, 0.5 mm, and 0.6 mm, while the core layer may consist of materials such as polyurethane, rock wool, or foamed plastic.
Thanks to the availability of specialized structural profiles, buildings constructed with color-coated steel-such as the Xiaotangshan Hospital built during the SARS outbreak-can be erected very rapidly, though they possess relatively low structural strength. The substrates for color-coated steel include cold-rolled steel, hot-dip galvanized steel, and electro-galvanized steel. The coatings themselves can be categorized into polyester, silicone-modified polyester, polyvinylidene fluoride (PVDF), and plastisol. Depending on the surface finish, color-coated steel products can be classified as standard coated sheets, embossed sheets, or printed (patterned) sheets.