How to prevent galvanized roofs from rusting

Galvanized steel roofs are common because they last long, cost less, and resist rust. If not maintained or exposed to harsh weather, they can rust. Different environments also affect how long aluminized zinc roofs last.

1. Know How Galvanization Works

Galvanized steel has a zinc layer that is usually 35–200 micrometers thick. It is applied by hot-dip or electroplating. The zinc protects the steel by corroding first and acting as a shield. Rust happens when the zinc layer is damaged or used up.

Important Point:

Roofing steel that is hot-dip galvanized is more resistant to rust than electroplated zinc.

The zinc’s life depends on the environment: 20–50 years in rural areas, but only 5–10 years near the coast or in industrial zones with high salt or pollution.

2. Check and Maintain Regularly

Steps:

Inspect the roof twice a year for scratches, chips, or white rust, which shows zinc corrosion. Focus on ridges, fasteners, and overlaps where water can collect.

Fix minor damage with zinc-rich primer or cold galvanizing paint. For deep scratches, clean the area with a wire brush and apply repair paint within 48 hours.

Warning Signs:

Rust spots that look reddish-brown, showing steel is exposed.

Peeled or flaking zinc coating.

Example:

A warehouse in Florida ignored small scratches on its zinc roof for three years. This led to many pits and cost $12,000 to repair. Fixing early would have cost less than $200.

3. Manage Environmental Factors

Actions:

Avoid water buildup by having a roof slope of at least 2:12. Install gutters and downspouts to remove water. Standing water speeds up zinc wear.

In coastal areas, rinse the roof monthly with fresh water to remove salt. Do not expose the roof to fertilizers, bird droppings, or industrial dust.

4. Prevent Mechanical Damage

Actions:

Limit walking on the roof. Use walkways or plywood sheets when needed.

Trim trees to stop branches from scratching the roof.

Remove snow with plastic shovels, not metal, to avoid scraping the zinc.

Data:

A 2023 report says 34% of galvanized roof failures happen because of mechanical damage during installation or maintenance.

5. Act Quickly When You Find Problems

Remove Rust: Use a wire brush, sandpaper, or chemical rust remover like phosphoric acid.

Clean the Area: Wipe with a damp cloth to remove residue.

Prime: Apply a zinc-rich primer.

Paint: Finish with a weatherproof topcoat.

Example:

A school in Australia used these steps to treat rust on its 10-year-old zinc roof. This extended its life by about 15 years.

6. Choose Good Quality Galvanized Steel

When buying:

Ensure zinc coating is G90 or higher, especially in coastal areas.

Look for steel with aluminum or magnesium in the zinc to help form a protective surface.

Check for standards like ASTM A653 or EN 10346 to confirm quality.

7. Use Climate-Appropriate Methods

In coastal areas, use stainless steel fasteners. Check the roof every 3-6 months.

Near industries, install filters to reduce chemical damage from acid rain.

In cold weather, add insulation and ventilation to prevent ice dams.