The conventional zinc flower surface formed after hot-dip galvanizing is the most fundamental treatment method. The average thickness of the zinc layer varies from 50 to 150μm. The size of the zinc flower is usually 3 to 8mm in diameter, and the surface roughness Ra value is within the range of 12 to 20μm. According to the test data from the European Coil Coatings Association (ECCA), the solar reflectivity of this type of surface is 0.65-0.75, and it is suitable for 85% of industrial building roof walls. The Energy Pavilion of the Dubai Expo Park, completed in 2022, uses conventional Galvanized steel plates. Under a 50℃ high-temperature environment, the measured temperature reflection efficiency reaches 68%, reducing air conditioning energy consumption by 32% compared to traditional concrete facades.
The finishing treatment (Skin Pass) eliminates zinc flowers through a reduction rate of 0.3%-1.5%, reducing the surface roughness to Ra 0.4-1.2μm. The automotive manufacturing industry has particularly strict requirements. For instance, the General Motors standard GMW3032M stipulates that the Ra value of the outer plate should be ≤0.8μm. The actual measurement data of Baosteel’s polished galvanized sheets in China shows that the adhesion of the coating has increased by 50% to 70%, and the incidence of orange peel defects has been compressed from 23% of conventional sheets to less than 5%. The battery tray brackets made by Tesla’s Shanghai factory using this process have the uniformity fluctuation of the electrophoretic paint film controlled within ±0.2μm, and the qualification rate has been increased to 99.1%.
Chemical conversion membrane treatment can enhance functionality. The chromate passivation film layer weighs approximately 0.5-3g/m², forming a protective layer 0.01-0.5μm thick, and the salt spray resistance time is extended by 300%. The verification of the material conveying system at the BMW Leipzig plant shows that the chromium-free blue-white passivated plate has a white rust area of only 3.2% in a 72-hour salt spray test in an environment with a humidity of 80%RH, which is far better than the 41.5% of the non-passivated plate. The phosphate-treated film can reach 2-5g/m², which is particularly suitable for building components that need to be coated. Nippon Paint experiments have shown that it can increase the adhesion of epoxy primer from 3MPa to 12MPa.
Coating composite technology doubles performance. When the thickness of the polyester (PE) coating is 15-25μm, the outdoor weather resistance life can reach 7-10 years. A fluorocarbon (PVDF) coating of 25-30μm can be extended to 20-25 years. The curtain wall of the Marina Bay Sands Hotel in Singapore is made of 70μm thick PVDF composite galvanized steel plates, which still maintain a light retention rate of 85% after 12 years of strong ultraviolet radiation from the equator. In the 2020 Sydney Airport expansion project, the HDPE film coating of galvanized steel plates increased the rainwater flow rate on the terminal building roof by 40%, with a peak drainage volume reaching 85L/s·m².
Innovate surface texture technology to expand application scenarios. Embossing treatment forms 3D patterns with a depth of 0.1-0.8mm, increasing the friction coefficient from 0.08 on a smooth surface to 0.35, and enhancing the anti-slip performance of the aerial work platform by 400%. During the construction of Ping An Finance Center in Shenzhen by China Construction Steel Structure Co., LTD., the accident rate of temporary passages made of diamond-shaped embossed galvanized steel sheets falling from them was zero. The matte treatment reduces the glossiness from 70GU to 5-15GU through a special cooling process, alleviating 90% of light pollution complaints. After the renovation of Terminal 3 at Tokyo Haneda Airport, the glare index dropped from 28 to 9.
Special alloy coatings meet extreme demands. The corrosion resistance of the 55% aluminum-zinc alloy coating (Galvalume) is 2 to 6 times that of the pure zinc coating, and it can reach 4,800 hours without red rust in the salt spray test. The coastal residential project in Texas, USA, adopted this material, and only 0.8% of corrosion points occurred within 20 years. Zinc-magnesium alloy coating has a significant advantage in cut protection. Tests by Mitsubishi Heavy Industries show that the corrosion resistance of the cutting edge has increased by 300%, and the maintenance frequency of construction machinery structural parts has decreased by 75%. The current EU regulation CPR on construction products requires that Galvanized steel plate must pass salt spray tests for more than 2,400 hours, pushing the market share of alloy coatings to 35%.