Steel trailers, whether they're hauling horses, landscaping materials or vehicles, can look downright embarrassing when an ugly shade of rust becomes the trailer's predominant color.
But a deteriorating paint job doesn't have to mean the end of the road for a trailer, as there's still a lot of life left in the body that's hiding underneath old paint and surface rust. Preparing the body surface and repainting the trailer's exterior don't require any special skills or professional paint equipment, and can make a trailer look like new in just one weekend.
Follow these easy steps, and get ready to step back in amazement as you admire your "new" trailer's much-improved finish. 
This is a good project for new DIYers
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Use a power washer to clean the trailer from top to bottom, inside and out.
Years of road travel and exposure to the elements while sitting outside have accumulated various types of grime on the trailer's surface, in crevices, and in other hard-to-reach places, even if at first glance the trailer looks pretty clean.
A standard nozzle/garden hose combo isn't going to deliver enough pressure to effectively remove all that dirt, mildew and other contaminants either. Instead, use a power washer and detergent to clean the trailer, starting at the roof and working your way down to the ground.
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Remove the rust.
To help ensure proper paint adhesion and a smooth finish, you need to remove the surface rust, as well as any deep, heavy rust, so that you're left with a surface that's smooth to the touch.
For lightly rusted surfaces, use a random orbital sander equipped with a sanding disc that's specified for metal use. For heavier deposits of rust, try a product such as rust remover first, before sanding. If it's a small area of heavy rust, consider using the POR-15 Stop Rust Kit. Wear eye protection and a respirator or mask to protect from paint dust and metal pieces.
For lightly rusted surfaces, use a random orbital sander | Rich Ellis
- Don't apply pressure to the sander. Just let it do the work, and keep it moving.
- Change the sanding pad periodically for best results, and remember to empty the debris-collection chamber or tray.
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Power wash the trailer again.
The rust-removal process undoubtedly will generate a lot of dust and debris, some of which will stick to the trailer.
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Tape over surfaces you don't want painted.
Once the trailer is completely dry, identify the specific parts you want to avoid getting paint on, including anything rubber or vinyl, windows, door handles, and chrome trim. To protect these areas and make the painting process go even faster, place tape over the surfaces and parts you don't want painted.
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Prime the surface.
To help prevent the reappearance of rust down the road, stop surface imperfections from bleeding through the final coat, and improve the final coat's adhesion to the trailer, first apply a coat of primer. Pick a primer color that's the same - or close - to your final coat.
Starting at the roof, use a roller and paint brush to apply the primer. For hard-to-reach spots, have a can of spray primer handy.
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Apply the final coat.
Once the primer has dried completely, use the brush, roller and spray paint to apply the final coat on the trailer. Choosing a gloss paint specifically designed for metal and a high-quality brush will deliver the best results.
A high-quality brush will deliver the best results | Rich Ellis
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Evaluate the finish.
Once the paint has dried, look closely at the finish and decide if a second coat will improve the results.
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Don't overlook the details.
If the trailer has steel wheels that have seen better days, clean, prime and paint them, too, to complete the trailer's restoration.
Don't overlook details like wheels. | Rich Ellis
Don't use the power washer nozzle's most powerful, pinpoint spray pattern as that will damage the trailer's surface. Instead, choose a wide spray pattern that doesn't mark the surface or remove paint. If it's an enclosed trailer and you're going to repaint the inside, repeat the cleaning process in there now, too.
When using a random orbital sander:
Choose a spot to paint the trailer that's in the shade or under some type of shelter. Direct sunlight can make the surface too hot and interfere with the paint's adhesion and drying.
No matter what your skill level is - beginner to advanced - if you can put paint on a paint brush, you can make an old trailer look new again, saving yourself a lot of money when compared to buying a new trailer.
