How to prevent galvanized roofs from rusting

Galvanized steel roofs have a longer life, are more economical, and resist rust. If not treated, they will rust if not handled in bad conditions. Other conditions vary widely, as well, and dictate the longevity of aluminized zinc roofs. Know How Galvanization Works. Galvanized steel consists of a 35–200 μm layer with zinc at its core. The material is applied by hot dip or electroplating. The zinc will corrode first and essentially act as the shield you put on steel. Rust is the destruction or depletion of the zinc layer. Important Point:

Roofing steel hot-dip galvanized has better rust resistance than electroplated zinc. The zinc is associated with a life: 20–50 years in rural areas but just 5–10 years when you’re on the coast or in industrial areas that have lots of salt or pollution. Check and Maintain Regularly. Steps:

Examine the roof twice a year for scratches, chips or white rust — artifacts that indicate zinc corrosion. Concentrate on ridges, fasteners and seams which invite water to collect. Use zinc rich primer or cold galvanizing paint for minor damage. Clean up and apply solution paint within 48 hours if the scratches are deep. Warning Signs:

Reddish-brown rust spots, that can suggest the steel is exposed. Zinc coating peeling or flaking. Example:

For three years, a Florida warehouse went undetected on the zinc roof by scratches in its roof. The result was many pits, which took $12,000 to repair. Repair done early would have cost below $200.

Manage Environmental Factors. Actions:

Remove the buildup of water with roof slope of not less than 2:12. Add some gutters/downspouts (to remove water). Standing water accelerates the wear of zinc. For coastal areas, rinse a roof every month with clean water to remove the salt. Do not expose the roof to fertilizers or bird droppings, or industrial dust. Prevent Mechanical Damage. Actions:

Limit walking on the roof. Incorporate walkways/plywood sheets where needed if you have to add walkways. Trim trees so that the branches do not scratch the roof. Remove snow using plastic shovels, not metal, to avoid scraping over the zinc. Data:

In the last year, a report published last month showed that 34% of galvanized roof failures come from mechanical issues in installation or service. When You See Issues, Get Actionable. Rust Removal: Remove rust with wire brush, sandpaper or a chemical rust remover like phosphoric acid. Wash the Site: Wipe with wet cloth. Prime: A zinc-rich primer. Paint: Wrap it topcoat, weatherproof. Example:

One school in Australia used these steps in an investigation into the treatment of rust on a 10 year old zinc roof. That increased its life expectancy by about 15 years. Select Quality Galvanized Steel. When purchasing:

If you use zinc, make sure the coating of zinc is G90 or more — particularly along the coast. Look for aluminum or magnesium in the zinc in the steel to help build a protective surface. Find standards — for instance, ASTM A653 or EN 10346 — for quality. Use Climate-Appropriate Equipment. If you’re using stainless steel fasteners in coastal locations, don’t hurry. Get to the roof every 3–6 months. Add filters around your businesses so less will be done by chemical damage from acid rain. In cold weather we insulate and vent to avoid ice dams.