How to Paint Rusted Surfaces
Metal is a wonderful, versatile, eco-friendly, and easily maintained material. One issue with it, though, is that most metal rusts at some point. If it contains even a small amount of iron, the metal will oxidize when exposed to air and moisture. Oxidation on iron and steel is easy to spot by its reddish brown color and its tendency to powder or flake off. Rust creates hard bubbles under paint, eventually erupting into lesions that erode the metal until it crumbles. If there is rust in your life, whether on tools, metal furniture, fittings, posts, or fencing, it is best to deal with it as soon as you can. Before you begin, here are a few steps to take when painting rusted surfaces.
WARNING: Before sanding or scraping rust off metal surfaces, you'll want to put on a face mask and safety glasses to keep metal particles out of your body.
Step 1 - Examine the Area
Identify the type of metal you are going to paint. Cast iron, steel, and galvanized steel have their own unique qualities and may require the use of slightly different products.
Evaluate the environmental conditions where the metal is located. Metal found on the outside of the house will undergo different conditions than metal found on the inside of the house. It would not be appropriate to use an interior metal paint on an exterior metal surface, so make sure you know what your project will be exposed to.
Choose the appropriate type of primer and paint. Metal paints and primers are rated for the various types of metal surfaces, so make sure to read the labels carefully to avoid repainting later on.
Step 2 - Prep Your Work Space
Establish a clean, well-ventilated working environment for the metal piece you are working on. This can be hard for stationary objects, so do the best you can. Remove any debris, dust, or cobwebs from the surrounding area and lay down clean newspapers or drop cloths.
With the planning complete, it is now time to tackle the rust.
Step 3 - Remove Surface Rust and Flaking Paint
Begin by scraping off all flaking rust. If space allows, a Dremel with a wire brush can reduce the time required for this step. Buzz the rust and old paint away. With this tool, you should be able to get down to bare metal without too much effort.
No Dremel? Use a hardened metal scraper or shave hook, which consists of a sharp-edged triangle-shaped steel plate attached to a handle. Some shave hooks have handles at both ends, allowing you to apply even pressure in a back and forth motion.
To remove stubborn layers of old paint, use a paint stripper to eliminate what the scraper missed. There are many natural and effective products on the market that are safe to use outdoors and within the home.
Step 4 - Sand and Clean
Sand the metal surface with medium to fine grit sandpaper to get down to the bare metal. Use a soft utility brush or clean cloth to remove any particulates or remaining abrasives. You can use the Dremel for this too. It is very important to work with a clean surface. Not only will the paint and primer adhere better to the metal, but the application process will go much more smoothly, resulting in cleaner, more professional looking lines.
If the metal is dirty or covered in grease of any kind, wash the surface of the metal with mineral spirits to breakdown and remove the grime. The surface must be completely clean for the remaining steps.
Step 5 - Prime
Apply the appropriate primer evenly across the metal surface. It is important to apply the primer evenly, completely covering the metal surface. For hard to reach areas, try using a soft cloth or small brush. If even a small area of metal is exposed, rust will again form, forcing a repeat of the process. It will save you time in the long run if you ensure a rust-free surface at this stage in the process.
Step 6 - Paint
Once the primer is completely dry, apply several thin coats of the desired paint color. Make sure to allow each layer to dry completely before moving onto the next one. Whatever you do, don’t get impatient at this point. Applying additional coats of paint before the first one dries can result in issues like bubbling, cracking, and wrinkling of the paint finish. Sometimes your paint will even peel off in clumps, leaving you no option but to sand it down and start again. With proper adherence though, your surface will look like new.
With your painting done, it is now time to sit back and enjoy the fruits of your labor. There are few things to keep in mind for the weekend warrior. Make sure to paint your rusted metal immediately upon completion of step two. It does not take long for metal to oxidize. Waiting even 24 hours can take you back to square one in the process. A job done right is definitely worth doing, especially when it helps transform an eyesore into something worth admiring.