1. Natural corrosion resistance of aluminum
When exposed to air, aluminum will quickly form a dense aluminum oxide (Al₂O₃) protective film (thickness of about 2.5nm), which can isolate oxygen and moisture from further erosion of the substrate and can self-repair after damage. Therefore, corrugated aluminum sheets will not rust in normal environments (pH 4.0-8.5, dry climate).
2. Conditions that may cause rust
Extreme environments
Acid-base corrosion: Environments with pH <4 (acidic) or >9 (alkaline) will destroy the oxide film. For example, long-term contact of chemical pipelines with strong acid solutions may cause pitting;
High-salt environments: Chloride ions in marine climates penetrate the oxide film and accelerate local corrosion (such as untreated corrugated aluminum sheets in coastal buildings).
Surface treatment defects
Insufficient oxide film: Aluminum materials that have not been anodized or sprayed (such as bare aluminum tubes) are easily oxidized in a humid environment to form white aluminum hydroxide powder (visually similar to "rust");
Mechanical damage: Scratches or impacts cause the oxide film to rupture. If it is not repaired in time, it may cause intergranular corrosion (common in aluminum plates that are improperly processed or transported).
Alloy type and processing technology
High-purity aluminum (such as 1060 series) has strong rust resistance, while aluminum alloys containing copper or zinc (such as 2024, 7075 series) are more prone to galvanic corrosion;
When the residual stress of forging or welding is not eliminated, it may induce stress corrosion cracking of aluminum materials (such as corrugated aluminum parts in industrial equipment).
3. Protection measures and improvement plans
Surface treatment technology
Anodizing: Form a 5-20μm oxide film on the surface of the aluminum plate through electrolysis, and the salt spray test life can reach more than 1000 hours (applicable to building supports); Fluorocarbon spraying: Cover with a dense coating layer, resistant to ultraviolet and chemical corrosion (such as outdoor curtain wall aluminum plate).
Environmental adaptability design
5052 aluminum-magnesium alloy is preferred in marine environment (salt spray resistance is better than 3003 series); Regularly clean and apply anti-rust oil (such as corrugated aluminum coil for storage).
4. Solution and repair of rust problem Mild oxidation: Wipe the surface with a neutral detergent (such as soapy water) to avoid acidic and alkaline solvents to aggravate corrosion; Local corrosion: Apply epoxy primer + topcoat after sandpaper polishing to restore the integrity of the protective layer.
Note: Through reasonable material selection (such as 6063T6 aluminum tube) and process optimization (such as high-frequency welding to reduce the heat-affected zone), the rust resistance of corrugated aluminum can meet most industrial and architectural needs.
