White rust, also known as wet storage stain or storage stain, is the white powdery substance that can form on the surface of a galvanised metal. This powder is a form of natural corrosion. This corrosion is damaging to both the aesthetic and the anti-corrosion layer the zinc provides. Zinc is quite durable and is used in galvanisation for its protective qualities; however, it is very reactive to water and produces ‘Zinc Hydroxide’ as a result. The rust progressively will eat at the protective zinc layer. This process is more likely to happen in wet areas with poor circulation.
Conditions That Determine if White Rust Forms
Storage Method: White rust forms quicker if metal is stored on top of each other or close together. Consider separating them when storing.
Air Circulation: Tightly packed steel limits air flow around the steel and therefore limits the ability for moisture to evaporate.
Climate: Areas of high rainfall like tropical places are often susceptible to moisture getting stuck in galvanised surfaces.
Storage Place: Storing the steel in any place exposed to moisture and the elements will increase the chance of white rust formation i.e. storing it outdoors.
Caring for Zinc-Coated Steel
- To maintain the aesthetic appeal of use some barrier protection like paint to prevent the normal corrosion
- Store zinc coated steel undercover and away from any sources of moisture. It is not recommended to use a tarpaulin because these trap moisture.
- Store away from open doors or windows to avoid exposure from condensation
- If products are exposed to water, avoid corrosion by allowing them to dry out.
If you have White Rust
What is White Rust?
To treat white rust damage, you can use vinegar and a nylon scourer or a wire brush wheel. After this, three coats of a zinc rich spray paint should be applied.