Your Reading List

7 Steps To Rust-Proof Your Trailer

You’ve seen them. Those rusty holes and spots that grow over time in grain trailers. “Rust is inevitable.” “You can’t stop it.” This is what you hear. If you read Benjamin Franklin’s quote “Nothing in this world is certain except death and taxes,” you will note that rust is not mentioned. Rust happens because we let it happen.

The only reason grain trailers and other vehicles rust out is that the rust is allowed to grow and accumulate on the trailer. Once the rust starts it will continue to grow with every rain shower, trip down a wet highway or even on days with a bit of dew. Add a dash of highway salt in the winter and it grows much more quickly. Fortunately for us rust can be stopped.

What makes me an authority on rust proofing grain trailers? Nothing. Until our son Ben bought one last year the closest I got to one was when a trucker picked up a load in our yard. However for the last twenty or so years in our body shop we’ve cleaned and rust proofed scores of vehicles. We’ve also repaired rust on likely hundreds of car and trucks. So here’s my limited wisdom on the subject.

How do we stop rust? First you have to understand what causes it. Water and steel are the key ingredients. That’s simple. What are the two types of rust that we will see on grain trailers? Rust that comes from the inside out and rust that starts on the outside and goes in. I’ll call them incoming and outgoing rust.

First let’s talk about incoming rust. On Ben’s trailer, 80 per cent of the rust damage has been caused by incoming rust. This is rust that starts from a small stone chip or mark on the paint and creeps under the paint. The area around the chip swells up to let in more moisture and the circle gets bigger and bigger until it rusts right through the side of the trailer. See pictures below. These pictures are of a trailer that’s only 11 years old.

Why does this incoming rust start? Poor paint. If this was properly painted the rust would not creep under the paint. Why wasn’t it painted properly? Because it’s very expensive to put proper primer on a unit the size of a grain trailer. We do it in our shop with every insurance repair as do the manufacturers when they make new cars and trucks, but grain trailers often just get the cheap paint.

How do you stop it? Very easily if you catch it early. Just touch up the rock chip with a bit of paint to keep the moisture away from the metal. This is quite easily done on the hood of your car if you have a few chips, but to get that touch up paint out and do all the chips on your grain trailer will take a bit of time. This is why a complete sandblast and repaint on a chipped up and somewhat rusty trailer will stop the incoming rust. Don’t let me stop you from doing a few touch ups, but be prepared to spend a bit of time on the job.

Now let’s talk about outgoing rust. Even if it is outgoing rust, it isn’t really friendly for your trailer. No matter how well you prime, paint and protect your outer areas on your trailer, the outgoing rust will eat right through the metal because it comes from inside the trailer. On pickups you’ve seen it. Those unsightly bubbles that appear magically over the rear wheels after a few years. That’s rust caused by dirt and moisture trapped inside the box sides. On grain trailers, it’s the

This is the front panel of the same trailer, with views from the inside and outside. In this case the dirt, which you can see on the photo taken from the inside, has held the moisture against the panel and rusted through to the front.

same thing. Dirt and moisture get trapped inside the metal seams and bracing under the trailer and the rust they cause slowly works to the outside. There are lots of moisture and dirt traps under those trailers. The only way to stop this rust is to keep the moisture away from the metal by cleaning away the dirt and salt and using a rust preventative solution. The photo taken from the inside of the trailer shows how dirt and salt build up can hold moisture and cause rust to form.


1. Clean the trailer. This is a dirty job. Don’t wear a Sunday suit. Wash the outside well. If you’re doing it by hand use a good brush to wash off the dirt and road film. Underneath it is usually easier to clean off the big lumps of dirt when they’re dry and then wash off the rest. Pay particular attention to those hidden nooks and crannies that trap dirt and water. If paint is peeling under there, then scrape off the peeled sections of paint. Let it dry well.

2. Inspect the trailer. Check out the rust damage and look for any cracks in the steel panels or frame. This is a sign of structural weakness. If the cracks are small, you can likely weld them up yourself if you’re a good welder.

3. Decide on a plan of action. This is when you say, “What have I got myself into?” If this is more than you can handle, call someone to do the job for you. If there is damage that you think could cause a safety problem and you can’t repair it properly, get professional help. If the damage is not serious and you’ve still got some energy, you can do it yourself. As in any job of this type, wear the correct protective clothing, masks and goggles as needed. Most of the stuff listed below is fairly easy to work with, but if you’re sensitive make sure to protect yourself and others.

4. Touch up the paint on the outside. Don’t grab the first can of white paint and merrily slobber it all over the trailer. You might find that when it dries it’s a different shade and the trailer looks like it has a skin disease. For touching up over paint chips and rust spots a good rust paint works well and it’s easy to use. First brush a bit on and let it dry for a day or two. Paint changes color when it dries. If it doesn’t match you can try tinting it by adding a bit of another color such as black, yellow, blue or sometimes red. (It would take several articles to explain paint matching, but this is all you get today.) If you want you can get the color code from the trailer manufacturer and get some paint mixed to that code at your local paint supplier or body shop. However this paint is designed to go over primer and unless you use a primer it will not adhere well. Rust paints are designed to adhere over rust, so primer is not usually needed. (NOTE: If the rust is severe, it may bleed through the rust paint. You may need to sandblast or use a rust converter. I’ll have more on this stuff in a later article.) Some sanding might be required but this is just touching up so don’t get too fussy unless you have lots of time.

5. Apply rust preventative to the inside. Once the dirt and crud is cleaned out inside you can see all the dirt and moisture traps. If you can keep the dirt and moisture out of these places it will help but in a lot of cases it’s not practical. We like to caulk up the seams on the outside of grain truck boxes to keep the moisture out. This involves sandblasting or sanding the metal, then priming, then applying the caulking and finally painting. On the inside of trailers where it’s all rusty, caulking will not stay in place unless you properly paint the metal first. This is too much work for most people. A good rust preventative like Rust Check (sold at Canadian Tire and other places) will work fine for this. I’ve also heard rumours that automatic transmission fluid works well, but I’ve never tried it. You could probably find a dozen other products that will do the job. The object is to spray enough Rust Check into the seams and crevices so that the Rust Check coats the metal and fills the seams. This works well on tight seams but if it’s anything over 1/32-inch wide, just try and make sure it’s well coated.

6. After a few days, wash the outside. You’ll have dribbles of Rust Check running down here and there, so get an old car wash brush and wash them off. Don’t get carried away with a pressure washer and wash off all the Rust Check on the inside or get too aggressive on the paint touch ups.

7. Do this every year or two, depending on usage and climate. If you keep ahead of the rust spots on the outside and keep it Rust Check’ed on the inside, your trailer’s lifespan will be increased quite a bit.

There you go. This is not an easy job, but it will save you money. Instead of paying many thousands for a professional paint job and repair or to replace your trailer, you can keep it looking good for years to come with some elbow grease and a few hundred dollars of supplies. If you’ve got a few holes in the trailer that need repairing, then just watch this spot because I’ll have an article on that in an upcoming issue.

Ron Settler, his wife, Sheila, and their sons Ben and Dan farm and run a repair and salvage business at Lucky Lake, Sask.

About the author

Ron Settler's recent articles



Stories from our other publications