When evaluating building and industrial materials, the core difference between Galvanized plates and aluminum plates lies in their corrosion resistance mechanisms. Galvanized sheets rely on the zinc layer on the surface of the steel substrate to provide sacrificial anode protection. According to the national standard GB/T 2518, the weight of the zinc layer is usually within the range of 60-275g/㎡. Under standard salt spray tests (such as ASTM B117), it is quite common for high-quality galvanized sheets to have an anti-corrosion life of 4,800 hours without red rust. In C3 (medium) industrial environments, the service life can reach 15 to 20 years. In contrast, aluminum plates (such as 3003/5052 alloy) rely on their naturally formed aluminum oxide passivation film. Although they do not require coating and have lower maintenance costs throughout their life cycle, they have a higher risk of pitting corrosion in environments containing chloride ions (CI-). For instance, empirical data from the coastal area of Mendoza, Mexico, show that The 2mm thick 5052 aluminum plate without coating showed significant pitting and perforation after six years, while the galvanized steel plate of the same zinc coating weight remained intact in appearance. Some non-load-bearing structures of the Hong Kong-Zhuhai-Macao Bridge take advantage of this difference. Aluminum plates are used to reduce weight in the dry environment inside the bridge body, while high-zinc-coated hot-dip galvanized plates are preferred in the splash zone and bearing positions.
Significant differences in mechanical properties significantly affect material selection decisions. The base material of galvanized steel sheets (such as S350GD+Z) usually has high strength characteristics, with tensile strength ranging from 340 to 550MPa, yield strength reaching over 350MPa, and elastic modulus approximately 200GPa. It is suitable for structures that need to withstand high loads, such as transmission towers (the design wind pressure load often exceeds 1.5kN/㎡). The advantages of aluminum plates lie in their lightweight and ductility. The tensile strength of 5052-H32 aluminum plates is approximately 240-270 mpa, and their elastic modulus is only one-third of that of steel (about 70GPa), but their density is only 2.7g/cm³ (about 35% of that of steel). This gives it a significant advantage in areas such as mobile equipment (such as high-speed rail carriage bodies), high-rise curtain walls (reducing foundation loads), and aviation luggage racks, with weight reduction of 30% to 50%. The super-large floating roof structure of the theme pavilion at the 2010 Shanghai World Expo required an aluminum-magnesium-manganese alloy panel thickness of 1.2mm to achieve the structural rigidity of 0.6mm for galvanized sheets. However, due to its weight being only 43% of the latter, it significantly reduced the steel usage of the main structure by approximately 18%.
Thermal conductivity and electrical conductivity are crucial for specific applications. galvanized plates retain the high thermal conductivity (about 50W/m·K) and excellent electrical conductivity (resistivity about 10^-7 Ω·m) of steel, making them the preferred material for electrical cabinet shells, grounding facilities, and some heat sink bases. Aluminum has better electrical conductivity (with a resistivity of approximately 2.8 x 10^-8 Ω·m, which is 61% of that of copper) and a thermal conductivity of about 235W/m·K, making it suitable for heat sinks (such as CPU coolers) and power busbars (under the same current-carrying capacity conditions) Aluminum fins weigh only 49% as much as copper and dominate in HVAC heat exchangers, such as evaporator/condenser fin materials. In solar photovoltaic support systems, aluminum supports, with a higher light reflectivity of over 25%, help cool the components (approximately reducing the backsheet temperature by 3-5°C) and increase power generation efficiency by 1%-2%. However, galvanized steel sheets are more commonly used in the foundation piles of large ground-mounted power stations due to their strength and cost (the unit price is often 35%-45% lower than that of aluminum sheets).
Life cycle cost (LCC) assessment requires a comprehensive consideration of initial investment and long-term benefits. At present, the average market price of 6061-T6 aluminum plates usually fluctuates within a range of 2.5 to 3 times that of galvanized steel plates (refer to the LME aluminum price of $2,300 per ton in 2024 vs. HRC steel price of $700 per ton), and the processing costs (such as welding and cutting) of aluminum are also 20% to 40% higher. In terms of maintenance, galvanized sheets require periodic anti-corrosion treatment in corrosive environments, while high-quality anodized aluminum sheets (with a film thickness of 15-25μm) can theoretically be maintenance-free for up to 50 years. In terms of recycling value, the residual value rate of aluminum is as high as 95% (much higher than the 60% of steel). However, in scenarios that require extremely high strength or impact toughness (such as construction machinery arms and forklift gantries), galvanized sheets are irreplaceable. An investigation into the roof collapse accident at Tesla’s California factory caused by heavy snowfall in 2019 revealed that the ultimate compressive strength of some aluminum purlins (150MPa) was only about one-third of that of the main beams of galvanized steel sheets of the same size (450MPa), and they were unable to withstand snow loads exceeding 38cm (compressive stress exceeding 20kPa). This indicates that simply comparing unit prices or densities during design and selection is a dangerous cost misunderstanding. In the field of building envelope systems, the cost of a 1.2mm thick galvanized plate (such as AZ150) may only be 65% of that of a 0.9mm thick 3005 aluminum plate, but the rust prevention maintenance expenditure over 25 years is expected to account for about 15% of the total initial investment.