ASTM A755/A755M-18 is a standard specification for metal steel sheets for externally exposed construction products. It covers metal steel sheets coated with metallic coatings by hot dip plating process and pre-coated with organic films by coil coating process. These steel sheets are available in the form of coils, cutting lengths and forming cutting lengths, and are widely used in construction fields such as roofing tiles, wall panels, etc. The standard specifies the performance requirements for metallic coatings and organic coatings of steel sheets, including coating adhesion, corrosion resistance, weathering resistance, etc., to ensure their long-term performance in the external environment.