Outdoor Metal Signs: What you Need to Know

Buying a plasma cut metal sign for outdoors? Here's what you need to know.

If you're buying a plasma cut sign for outside you may need to take some extra steps with it before it's mounted, depending on the finish you want.

Rusty Metal Signs and Art

If a rusty metal sign or piece of metal yard art is the look you're going for, simply leave your mild steel item outside for nature to do her magic and naturally rust the sign.

Take care where you rest your item though, as rust can stain surfaces, and if a metal item is left touching against a wall or resting on a window ledge some orange marks may start to appear!

To avoid this situation, once your item has rusted to a point you're happy with it you can seal it with some coats of clear lacquer or varnish or, for a more natural look, apply some beeswax or linseed oil. This will inhibit the rust, but not stop it entirely, and will need to be reapplied every 6 months or so.

Rust not your thing?

If you don't want a rusty sign, there are a few different options for sealing metal signs to go outside, depending on your budget and how you want the sign to look.

Painting a Metal Sign for Outdoors

Painting your sign is the most affordable option as you can do it yourself fairly easily.

All you need to do is sand the item to "key" the metal so paint will stick to it, degrease it with some white spirit or similar, and then paint it.

If you're painting a metal sign for your garden make sure you choose a paint that is suitable for outdoor use, such as Hammerite. 

Powder Coating a Metal Sign for Outdoors

If you choose to get your metal sign powder coated by a specialist powder coater it will cost more, but your sign will have a more hard wearing finish than paint.

Powder coating is exactly what it sounds like- a fine powder is sprayed onto the item then baked in an oven to set it. 

When choosing a powder coater find someone who has experience of working with flat signs and ask to see examples of their work if possible. You should tell the powder coater that your sign is for outside so a primer will need to be used first. Powder coating doesn't give as shiny a finish as paint but it should be a flat finish without any runs in it.

Galvanising a Metal Sign

Galvanising is another option for outdoor metal signs. Galvanising is the process of dipping a mild steel item in a bath of molten zinc to form a protective layer around it.

Galvanising gives a more agricultural finish than paint and powder coating. It's commonly used for farm gates and will typically be quite textured, but the thick coating should last a lifetime. It's usually a metallic silver when done but will dull off over time and can be painted over.

Wood and Metal Signs

If you plan on mounting your metal sign onto a piece of wood you need to take (even more!) care.

Mild steel that isn't treated or sealed can react with certain types of wood like oak when it gets wet, turning it a dark blue/ black colour. So if you find yourself asking "why has my oak turned black?!" it's because the oak has been in contact with some iron.

The iron in mild steel draws the tannin acid out of the wood, turning the wood black and making the metal sign feel greasy. This process happens when the sign gets wet or is in a damp area, like outside.

If your metal sign is going to be in a covered area you can use linseed oil or beeswax on the metal which will inhibit rust (although not entirely prevent it).