Corrosion is one of the most common problems which affect a metal roof. While metal roofs are generally coated to prevent any rusting for a very long time, if the roof gets scratched, it can be affected by humidity, oxygen and sunlight which cause corrosion. Apart from making the roof look unaesthetic, rust can also cause structural weakness which could cause the roof to leak, or even collapse. If you notice rust on your roof, it should be immediately repaired to prevent further harm.
Here is what you should do, if your metal roof starts to show signs of rust.
Firstly, scrub the rusted area of the roof with a wire brush to remove any dirt, old paint, loose rust, moss, etc. If the debris is hard to remove, you can use a metal scraper as well. After you have scrubbed all the loose particles, rinse the area to ensure that it is completely removed. After washing, dry with a clean piece of cloth or some paper napkins.
On the rusted portion, apply some naval jelly. Ensure that you follow the instructions given on the packaging. When handling string chemicals, always remember to wear protective gear like safety goggles and rubber gloves to avoid getting burned. Leave the jelly on for around half an hour, or till all the rust is dissolved.
Wash the metal with water to remove the naval jelly, and dry the area again. If you notice any rust marks still present, remove it by rubbing diagonally using sandpaper. You can also use an orbital sander, if you are comfortable with using the machine. Wipe the area with a piece of cloth soaked in mineral spirits, and then allow it to air dry.
After rinsing and drying the area, check one last time to ensure that it is free from all impurities. Using a roller brush, apply a coat of rust resistant primer. Leave it on for the amount of time recommended by the manufacturer for it to dry. After the primer dries, apply two coats of acrylic paint in the color you want. The painting has to be done quickly because even though all the rust has been removed, it could return within a day.
In case your roof is severely rusted, you might need to apply a patch on the affected portion after cutting out the area or change the sheet altogether. That process is harder than just removing rust. It is advisable to seek professional help in case you are not comfortable doing it yourself.
After your paint has dried, your roof will be free from rust for a very long time. The roof can be slippery and dangerous. Remember to take all necessary precautions while working on it.