Rust is caused when iron comes into direct contact with water and oxygen. Technically, rust comes from a chemical reaction between carbon dioxide from the air, water, and iron. Rust is nothing more than simply corroded iron. When oxygen combines with water then iron is dissolved.
Florida’s climate makes corrosion and rust on weather exposed metal substrate commonplace. Typically, once rust is discovered within a metal substrate the entire substrate should be properly stripped down to “white metal” cleaned, primed & painted.
Spot priming of the rusted area is only a short-term temporary fix. Once Rust is in metal the rust will continue to spread. If one area is treated, it is likely that rust will breakout elsewhere. The following steps are essential when corrosion resistance is required. Corrosion resistance painting systems are a challenge in our climate. Maintenance is a necessary process in rust or corrosion resistance.
- Sand blast, wire wheel, or wire brush all crusty, mill scaled surfaces to a smooth, rust-free condition. Ultimately, sand blasting to an SSPC 6 commercial blast is superior to hand techniques of rust removal. Any rust not removed will continue to corrode underneath new coating systems. All five sides need to be treated equally (exterior face, (2) side ends, (2) top and bottom ends.
- Wipe down the prepared surface with mineral spirits or VM&P Naphtha to remove residues, dust, and grease, and let dry.
- Apply a full coat of UCI #3-2200 "ULTRA-PRIME" Rust Inhibitive Flash Bond Industrial Primer at 150 SQFT per gallon Brush, roll, or spray, application. Taking care to lay the product on heavy so that no brush marks show. When priming, thicker is better.
- Apply two coats of the prescribed industrial enamel, urethane or 100% acrylic finish coat, yielding a total system of three complete opaque coats over all metal areas. The goal is to build up enough mil thickness in separate coats to minimize skips, holidays, and thin spots. When using an acrylic topcoat, repeat step 3 for 2 full coats of primer.
UCI makes no guarantee of the success as to the longevity of the coating system against rust re-occurring. However, following these guidelines by preventing water and oxygen from attacking the metal surface will minimize the return of rust.
Caution: Galvanized steel should never be primed with alkyd paints. UCI 'S ULTRA-PRIME can be used for all types of metal. For spot priming with ULTRA-PRIME check compatibility with any previous coating remaining on substrate,
Sometimes it may be cost effective to replace a door rather than prepare and repaint. There are numerous hurricane approved doors that are not made of metal then rusting is not an issue.