How Aluminium-Zinc Coated Roofing Sheets Help Resist Corrosion
Aluminium-zinc coated roofing sheets are widely used to improve the corrosion resistance of steel roofs. You will learn what this coating is made of, how it resists corrosion, and where it is most effective. We also explain how roofing steel sheets in Kerala cope with monsoon and coastal air, how they compare with ordinary GI sheets, and what to check before you choose a sheet.
What Are Aluminium-Zinc Coated Roofing Sheets?
Aluminium-zinc-coated roofing sheets are steel sheets coated with a thin alloy of aluminium, zinc, and a small amount of silicon. The steel underneath carries the load, while the coating shields it from moisture and air.
The commonly used alloy contains about 55% aluminium, 43.4% zinc and 1.6% silicon by weight. Silicon helps control the reaction between the molten coating and the steel during manufacturing.
The thickness and yield strength of the steel determine the sheet's structural strength. The corrosion resistance in the long run depends upon the quality and composition of the coating.
How Does Aluminium-Zinc Coating Help Resist Corrosion?
Aluminium-zinc coating protects steel from rust in two ways. Aluminium forms a protective barrier against moisture and oxygen, while zinc helps protect exposed steel at scratches and cut edges by corroding first. So the steel stays protected even when small parts of the coating get damaged.
Aluminium Creates a Protective Barrier
When aluminium comes in contact with air, it forms a thin, stable oxide layer on the surface. This layer is dense and slows the movement of water, oxygen, and salts towards the steel.
The barrier keeps working season after season, which is why the sheet holds up in damp weather. It works best while the coating stays unbroken, so clean surfaces and good drainage still matter.
Zinc Provides Sacrificial Protection
Steel becomes exposed at scratches, cut edges, and drilled fastener holes. At these spots, zinc corrodes in place of the steel, which delays red rust around the damage.
This protection covers small areas only. Wide scratches or missing coating need proper repair, so deal with visible damage early using a method the manufacturer recommends.
Coating Quality Influences Corrosion Resistance
Coating mass refers to the total metallic coating applied to both sides of the sheet, measured in grams per square metre. Common specifications include AZ70 and AZ150.
A higher coating mass generally provides greater corrosion resistance, particularly in harsh environments. However, deep scratches, damaged edges, and exposure to harmful chemicals can still reduce its effectiveness.
What Are the Benefits of Aluminium-Zinc Coated Roofing Sheets?
Aluminium-zinc coated roofing sheets offer improved corrosion resistance, reduced maintenance needs, and suitability for different roofing applications. Their performance depends on coating quality, proper installation, and environmental conditions.
- Better corrosion resistance and lower upkeep: The coating reduces rust-related repairs, so regular cleaning and inspection are usually the main care a roof needs.
- Suitable for homes and commercial roofs: The same material is used on houses, shops, workshops and godowns.
- Better performance in wet and humid places: Long rainy spells and constant dampness are where plain steel struggles, and coated sheets handle them better when the roof drains well.
Are Aluminium-Zinc Coated Roofing Sheets Suitable for Kerala?
Yes, aluminium-zinc coated sheets suit Kerala when the coating mass matches the site, and the roof is installed and drained properly. Rain, humidity, and coastal salt are the three conditions that decide how long roofing steel sheets in Kerala last.
Heavy Rainfall and Humidity
It’s worse for a roof to retain water than to drain water. Check that the gutters and slopes are clear. Leaves and dirt hold moisture against the sheets.
Check the roof before and after the monsoon for scratches, loose fasteners, and rust marks. We suggest fixing small damage early, since damp weather helps it spread.
Coastal Exposure and Installation Requirements
Near the coast, salt forms on the roof and attacks exposed metal faster. Use compatible fasteners, and keep copper and other reactive metals from touching the coating.
Follow the manufacturer’s recommendations for protecting cut edges and roof joints. Proper cleaning will also assist in removing salt build-up.
For locations exposed to severe marine conditions, confirm that the product suits the site rather than assuming it does.
Aluminium-Zinc Coated Roofing Sheets vs. Ordinary GI Sheets
Aluminium-zinc coated sheets use a coating made of aluminium, zinc, and silicon, while ordinary GI sheets have a zinc-based coating. Aluminium-zinc sheets generally offer better atmospheric corrosion resistance under many exposure conditions, though performance depends on coating mass, surface condition, and the surrounding environment.
| Feature | Aluminium-zinc coated sheets | Ordinary GI sheets |
| Coating composition | Aluminium, zinc, and silicon alloy | Zinc only |
| Corrosion protection | Barrier layer plus sacrificial zinc | Mainly sacrificial zinc, which wears away over time |
| Maintenance | Routine cleaning and inspection | Routine cleaning and inspection based on exposure conditions |
Coating mass matters as much as coating type. Ask for the coating mass in grams per square metre and compare sheets with similar values before you compare prices.
Why Explore Luxume Roofing Solutions?
At Luxume, we have manufactured colour-coated steel sheets from Ernakulam since 2011. We supply roofing steel sheets in Kerala in three ranges: Luxume, Luxume+ and Luxume Silverlux.
Luxume carries an AZ70 aluminium-zinc coating, while Luxume+ and Luxume Silverlux carry AZ150. All three use IS 15961 grade steel with a minimum yield strength of 550 MPa, and the technical data sheet for each range lists the full specifications.
If you are unsure which coating mass suits your roof, contact Luxume and our team will help you choose.