Your old, galvanized metal has taken a bit of a beating from the elements and has started to mar the overall appearance of your home. However, you think it is still structurally sound enough to last a few more years. All it needs is a coat of paint. Before painting the roof, however, use the following three steps to remove any rust and prevent it from forming in the future
Step 1: Remove The Top Layer Of Excess Rust
The first step involves clearing away the top layer of rust. This will prepare your roof for the next step where you will be removing it at its core. You will need a steel wool, a long-handled, steel-bristled brush, and a push broom for this step.
Using firm pressure and a circular motion, scrub every rusty area of your roof with the steel-bristled brush. This will loosen most of the oxidation from the rust's outer layer. For thin areas, it should remove almost all of the rust that you can see.
Sweep the area with the push room to clear away the dust. Doing this will give you a better view of the thicker portions. If you cannot remove these with the steel brush, use the same technique with the steel wool to loosen the deeply embedded rust. Then, thoroughly sweep the area once again using the broom.
While you are performing this step, be on the lookout for any thin or flaking metal. If you come across any, be gentle while you are scrubbing, since you could cause more damage.
During this process, if you find any areas that have holes, you may want to talk to a roofing professional about inspecting the roof before proceeding with the project. If there is too much damage, those portions of the roof may need to be replaced to prevent leaks.
If you do not find any holes, go on to step two.
Step 2: Wash The Roof With Oxalic Acid
Oxalic acid combats rust in two ways. It dissolves the existing rust particles, removing any that already exists. It also coats the metal and prevents the oxidation process from taking place. The oxalic acid solution can be purchased at home improvement centers and the hardware section of most department stores.
You will need a large mop, a five gallon bucket, a gallon of oxalic acid, and a garden hose with sprayer. You also need to wear personal protective gear, such as rubber gloves, mask, and safety glasses, since the acid can have adverse effects on your body when you are exposed to it.
In the five gallon bucket, mix together the gallon of oxalic acid and three gallons of water. Saturate the mop in the solution and wring it out.
Mop the surface of your roof. Allow the liquid to remain for two hours to fully clean the metal.
Rinse off the acid with the garden hose. Let it air dry for four hours before going on to the next step.
Step 3: Prime The Metal With A Rust Inhibitor
Now that you have removed most of the existing rust, it is time to apply the undercoating for your first coat of paint. This undercoating needs to be a primer that contains a rust inhibitor that will prevent moisture and oxygen from reaching the metal. Without these two key ingredients of the oxidation process, rust cannot form.
Use a roller brush to apply a thin layer of the primer on the entire surface of your roof. Allow it to dry and repeat with a second coat.
After following these steps and removing the current rust, you should have no problems with it in the future once you paint it. As you go through the process, however, you may find that the rust has badly deteriorated the metal, making it very thin, flaky, or holey. If so, you may want to talk to a roofing contractor about either replacing these areas or installing an entire new roof.