Is Galvalume superior to galvanized in all conditions

The corrosion resistance of aluminum zinc coated coils (such as 55% aluminum zinc alloy, commonly known as Galvalume) is superior to that of ordinary galvanized coils (pure zinc coating) in most environments, but not all environments are suitable. Its advantages and limitations need to be analyzed in conjunction with specific corrosion conditions.

Aluminum will dissolve at pH>9, causing the corrosion rate of aluminum zinc coated sheets to exceed that of galvanized sheets in concrete pouring or alkaline soil.

At this time, galvanized sheet or an additional isolation layer (such as epoxy coating) should be used.

The sacrificial protection of aluminum zinc plating (zinc) is limited to local areas, and edge corrosion may be more pronounced than that of galvanized sheets (the sacrificial anode effect of galvanizing is more comprehensive).

Acidic condensate (industrial waste gas) may cause pitting corrosion of aluminum zinc plating, while galvanized sheet exhibits uniform corrosion.

Stronger corrosion resistance – In coastal, industrial areas, and high humidity environments, the aluminum oxide film (Al ₂ O3) provides stronger protection and typically has a lifespan 2-6 times longer than galvanized steel.

Better high-temperature resistance – suitable for high-temperature environments such as roofs and high-temperature exhaust components.

Better economy (long-term) – Aluminum zinc coated steel has lower long-term maintenance costs in corrosive environments.

Application environment:

Coastal areas, industrial pollution areas, weak acid rain areas, and high temperature and high humidity climates.

Typical applications: Color coated substrates, roofs/exterior walls, automotive exhaust pipes (external).

Alkali resistant environment (pH>9) – Galvanized steel is more corrosion-resistant in contact with concrete or highly alkaline soil (such as building steel bars, underground pipelines).

Better incision protection – The pure zinc layer of galvanized steel provides more comprehensive sacrificial protection for cutting and welding parts (suitable for parts that need to be processed).

Lower cost (short-term) – Galvanized steel has lower initial costs in dry or weakly corrosive environments.

Application environment:

Cutting parts that require comprehensive sacrifice protection in alkaline environments (contact with concrete).

Typical applications: steel reinforcement brackets, underground pipelines (requiring coating).

Strong acid/strong alkali, high salt and high temperature (such as chemical plants): Use stainless steel, nickel based alloys or organic coated steel plates instead.

Aluminum zinc coated steel coils have better corrosion resistance than galvanized steel sheets in most natural and industrial environments, but may perform even worse in alkaline environments, localized damage, or extreme chemical conditions. The selection should be based on specific environmental parameters, cost, and lifespan requirements, and if necessary, verified through salt spray testing or on-site hanging.

Wanzhi Steel exports a large amount of galvanized steel coils and aluminum zinc coated steel coils every year. We have a professional team and a complete production line, which can provide professional services and high-quality products for every customer. Welcome to inquire and place orders.