Why are the requirements for color-coated metal sheets in home appliances so high

The requirements for color-coated metal sheets used in home appliances are far more stringent than those for construction materials. The critical distinction lies in the fact that these sheets are directly exposed to the consumer's view; they must simultaneously satisfy the dual, rigorous standards of a "zero-defect appearance" and "30-year-grade durability." Color-coated sheets serve as the final exterior material for finished appliances—such as refrigerators and washing machines—and are marketed and sold without undergoing any secondary painting processes. In retail showrooms, consumers inspect these products at close range and make repeated comparisons; consequently, even the slightest scratch, color deviation, or inconsistency in gloss can result in a product return. This makes them "one of the steel products with the most exacting surface quality requirements," far surpassing those for color-coated sheets used in construction. High Precision Requirements for Substrates: The galvanized substrate must be free of shape defects—such as wavy edges, warping, or camber—as such imperfections could scratch the coating rollers during high-speed application, thereby triggering linear coating defects. Precise Control of Coating Thickness: Coating thickness directly impacts corrosion resistance (accounting for up to 19.1% of durability), production costs, and processability; therefore, it must be optimized to the absolute maximum while ensuring that all performance criteria are met.