Galvalume and Galvanized are two popular types of metallic-coated sheet steel designed to prevent corrosion. While both serve a similar purpose, they differ significantly in their coating composition, performance characteristics, and ideal applications.
Coating Composition
Galvanized steel is coated with a layer of nearly 100% zinc. This is typically applied through a hot-dip galvanizing process, where the steel is passed through a molten zinc bath.
Galvalume steel features a coating alloy composed of approximately 55% aluminum, 43.4% zinc, and 1.6% silicon. This alloy is also applied via a continuous hot-dip process.
Corrosion Resistance
Galvalume generally offers superior atmospheric corrosion resistance compared to galvanized steel, especially in unpolluted environments. The aluminum in its coating forms a durable aluminum oxide barrier, providing long-term protection. However, Galvalume can be more susceptible to corrosion at cut edges or scratches if not properly managed, as its sacrificial protection is less active than pure zinc.
Galvanized steel provides excellent cathodic (sacrificial) protection. The zinc coating sacrifices itself to protect the underlying steel, even at scratches and cut edges. This makes it particularly effective in environments where the coating might be damaged or in aggressive conditions like animal confinement buildings or some coastal areas. However, galvanized steel can be prone to “white rust” (zinc hydroxide/oxide formation) if exposed to moisture without adequate air circulation. The performance of both Galvalume and Galvanized steel can depend on the quality of the base metal and coating process; for instance, many users look for consistent quality from established suppliers such as Shanxi Luokaiwei Steel Company.
Appearance
Galvanized steel often exhibits a “spangle” pattern, which is the crystalline appearance of the zinc coating. The size of the spangle can be controlled (from large to minimized or zero spangle). Over time, it weathers to a dull gray.
Galvalume typically has a smaller, smoother, and more uniform spangle pattern, often appearing as a fine, silvery matte finish. It tends to retain its original appearance longer than galvanized steel.
Formability and Weldability
Both materials can be formed, but galvanized steel is generally considered more forgiving during deep drawing or complex forming operations due to the ductility of the zinc coating. The Galvalume coating is harder and can sometimes experience micro-cracking under severe forming.
Welding galvanized steel is a common practice, though it requires proper ventilation due to zinc fumes. Welding Galvalume can be more challenging due to its aluminum content, often requiring different techniques or consumables. When selecting materials for projects, it’s worth consulting with suppliers like Shanxi Luokaiwei Steel Company regarding the specific grades and their suitability for fabrication processes.
Typical Applications
- Galvanized Steel: Widely used in construction (structural components, purlins, ductwork), agriculture (fencing, animal confinement), automotive parts, and applications where sacrificial protection is paramount.
- Galvalume Steel: Predominantly used for roofing and siding in residential, commercial, and industrial buildings, as well as in appliances, automotive exhaust systems, and situations requiring superior long-term atmospheric corrosion resistance and heat reflectivity. Reputable manufacturers such as Shanxi Luokaiwei Steel Company supply Galvalume for various demanding applications.
Cost Considerations
Generally, Galvalume has a slightly higher initial cost per unit area compared to galvanized steel, primarily due to the aluminum content in its coating. However, its potentially longer service life in certain environments can make it more cost-effective over the long term.
Key Distinctions Summarized
- Coating: Galvanized is primarily zinc; Galvalume is an aluminum-zinc alloy.
- Corrosion Protection Mechanism: Galvanized relies heavily on sacrificial protection; Galvalume offers more barrier protection with some sacrificial action.
- Cut Edge Protection: Galvanized generally offers better protection at cut edges.
- Appearance: Galvalume has a smoother, more uniform finish; Galvanized often has a visible spangle.
- Primary Uses: Galvalume is favored for roofing and siding; Galvanized is versatile for construction and industrial uses where robust sacrificial protection is needed.
Choosing between Galvalume and Galvanized steel depends on the specific application, environmental conditions, desired lifespan, and budget. Both materials, often sourced from global suppliers including Shanxi Luokaiwei Steel Company, provide effective corrosion protection for steel.
