1.How does 55% aluminum-zinc alloy coated coil perform in a highly corrosive environment?
Advantages: Excellent corrosion resistance: Aluminum forms a dense aluminum oxide protective layer, providing excellent barrier protection (especially corrosion resistance to the atmosphere, ultraviolet rays, and industrial pollutants far exceeds that of pure zinc). Zinc provides sacrificial anode protection (especially on cut edges and scratches). Its comprehensive corrosion resistance is usually 2-4 times or even higher than that of pure zinc coatings of the same thickness.
Excellent heat resistance/high temperature oxidation resistance: It can resist high temperature environments (such as high temperatures in certain industrial environments or under sunlight) better than pure zinc coatings.
Good UV resistance: The aluminum component is more stable and is not easily affected by UV aging.
Chloride ion corrosion resistance: It performs much better than ordinary galvanizing in seaside (salt spray) environments.
Application: It is one of the preferred solutions for industrial areas, polluted areas, coastal areas, and roofs and walls that need to be exposed to ultraviolet rays for a long time.
2.What are the advantages of zinc-aluminum-magnesium coated coils in highly corrosive environments?
Super strong corrosion resistance: Especially strong incision protection and red rust resistance. The addition of magnesium significantly improves the self-repairing ability of the coating, which can more effectively seal cuts, scratches and edges to prevent corrosion from spreading. At the same coating thickness, its corrosion resistance (especially salt spray test performance) is usually 5-10 times or even higher than that of ordinary galvanizing.
Excellent resistance to pitting and scratch corrosion: Very suitable for environments susceptible to mechanical damage or high salt levels at the seaside. Good resistance to industrial air pollution: Strong resistance to pollutants such as SO2.
Longer service life: Can significantly extend the life of components in extreme environments.,
3.Can ordinary hot-dip galvanized coils with high zinc layer weight be used in highly corrosive environments?
Advantages: Relatively low cost: cheaper than alloy coating.
Sacrificial anode protection: protects against cuts and scratches.
Limitations: At the same thickness, the corrosion resistance is much lower than GL and ZnAlMg. The coating thickness (zinc layer weight) needs to be significantly increased to compensate, such as choosing Z600 (600g/m²) or even higher specifications (such as Z275 is only 275g/m², and the life is limited in harsh environments).
High temperature oxidation resistance and UV aging resistance are not as good as GL.
Weak pitting resistance in salt spray environment.
4.What are the key factors in selecting galvanized steel for highly corrosive environments?
Coating Type: ZAM/Magnelis etc. > 55% GL/Galvalume >> GI with extra high zinc coating weight. ZAM is the best solution for the most demanding environments (especially seaside).
Coating Thickness/Weight: Whichever type you choose, go for higher coating thickness/weight. Thicker coatings mean more sacrificial material and longer protection.
Surface Treatment (Passivation): Choose a high quality chrome-free passivation (such as ENVIRONMENTAL Chrome-Free Passivation) or anti-fingerprint coating. This provides additional temporary protection against rust (white rust), improves fingerprint resistance, and serves as a good base for subsequent painting. Avoid low quality passivation or unpassivated products.
Substrate Quality: Make sure to use a steel grade that meets the requirements, with good mechanical and weldability.
Design Details: Even with high performance coatings, good design (avoiding water accumulation, providing ventilation, protecting cut edges) can significantly extend service life.
5.Summary: What should we choose for areas with severe pollution, high UV radiation, industrial areas and coastal areas?
Best choice: zinc-aluminum-magnesium coated coil (such as Magnelis, ZAM) - provides top-level comprehensive protection, especially good at resisting cut corrosion and salt spray corrosion.
Excellent choice: 55% aluminum-zinc alloy coated coil (GL/Galvalume) - cost-effective, excellent atmospheric corrosion resistance, heat resistance, and UV resistance, a common and reliable solution for harsh environments.
Basic choice (caution required): ordinary hot-dip galvanized coil with ultra-high zinc layer weight (GI, such as Z600) - the lowest cost, but the thickness must be sacrificed in exchange for life, and the performance is far inferior to the previous two. It is only considered when the budget is extremely limited and the environment is relatively less harsh.