Painting over metal makes rusty doors, mailboxes and railings look brand new again, but just like painting wood or any other surface, painting metal necessitates the use of the right paints. Carelessly painting metal without understanding the differences between coatings and their intended uses can result in paint failure. Unlike wood surfaces, metal forms rust through oxidation, and the rust can destroy a new paint finish if you use the wrong paints.
Following the use of primer, oil-based paint forms a tough coating on metal and inhibits the formation of rust and corrosion. Oil-based paints are ideal for steel doors in a working environment, exposed to frequent passer-by traffic. The thick and lustrous finish of oil paint allows thorough cleaning, without compromising the finish itself. Oil-based paints stand up to the elements of weather and their versatility allows application on metal swingsets, toys, doors and mailboxes. On the downside, oil paints release pungent fumes. Wear protective gloves to keep hands free from sticky paint stains.
Acrylic Latex Paint
Acrylic latex paint is a cost-effective alternative to pricey oil-based paints and enamel. Exterior acrylic paints provide durability similar to oil-based paints and lack the smelly fumes and messy cleanup. Acrylic paint on primed steel doors, exposed to frequent sunlight, will last longer than a coating of oil-based paint. Acrylic paint is the recommended and most common coating used for exterior aluminium siding on homes. Clean and prime metal surfaces such as aluminium siding with a primer suited to the aluminium or other metal type prior to applying the first coat of acrylic latex paint.
Industrial enamel is a heavy-duty oil-based coating used for steel doors, metal staircase railings and equipment in industrial or factory settings. Industrial enamel dries into a hard coating with a high-gloss finish. These coatings are extremely smelly and require the use of respirators to evade the foul fumes during application. Industrial enamel takes longer to dry than latex coatings, which necessitates careful application to avoid build-up and running paint. Industrial enamel does not block rust on its own unless the enamel contains special rust-inhibitive properties.
Rust-Blocking Paint and Primer
Rust-blocking paint products contain zinc chromate, which inhibits the development of rust on a metal surface. Specialised all-in-one paint and primer products eliminate the time-consuming task of applying a separate coat of primer on metal. The all-in-one advantage reduces time, paint and material expense, and provides long-term protection for metal surfaces. For the best results, rust spots require sanding, followed by two to three coats of the paint. Rust-blocking paints are sold in oil-based and acrylic products.