Quality Inspection of White Al-Zn Coated Sheets

Quality inspection of white Al-Zn coated sheets is a systematic quality control process strictly following standards like GB/T 14978-2023 and ASTM A792, covering full-dimensional verification of the product’s performance and appearance. First, full visual inspection is carried out under 40W daylight to check for surface defects such as missing plating, exposed substrate, scratches, uneven spangles, color difference and residual fingerprints, ensuring the white coating is uniform and free of abnormal stains. Then dimensional verification is performed, detecting thickness, width and flatness deviations with tools like vernier calipers, to confirm all dimensional tolerances meet the specified requirements. Core coating performance tests are the key links: the double-sided coating weight is measured via chemical dissolution method, while XRF spectroscopy verifies the standard 55%Al-43.5%Zn-1.5%Si composition ratio. Coating adhesion is tested through 180° cold bending and cross-cut test, ensuring no peeling or powdering occurs. Neutral salt spray test is also conducted, where qualified passivated sheets show no white rust for over 480 hours. Finally, tensile tests are implemented to verify the substrate’s yield strength, tensile strength and elongation, ensuring the sheets meet the mechanical requirements for subsequent stamping and forming applications.