Painting Vehicle Sills to Prevent or Repair Rust

Hi there. This is my first instructable, I've been wanting to do one for a while and I figured this is as good as any to start with. My little van is a Suzuki Carry 1.3, which has lived by the sea for at least the past 5 years. It's an old vehicle, and has therefore had some wear, resulting in some rust. When I bought this vehicle one sill had a small hole in, which on further inspection was a whole area of thinned metal. I took it to my local garage, and they cut and welded a new plate in place. The result of their work was an area of black underseal painted over a welded patch, looking a little silly. I had already decided I was going to paint the sills, and this worked well since half was painted already. So, enough of me ranting, lets get on with the instructable !

Step 1: Preparation

To start with you will need a few tools. Obviously you will need paint. I used a tin of Hammerite Underbody Seal which I bought for under £12. It is made using waxoyl and dries to a tacky finish. This means that any stones will not chip it, and any flex will leave it undamaged. I also bought a cheap disposable paintbrush of 40mm width. This cost me 99p delivered from amazon. As well as these, you will need a roll of painters masking tape. No idea what this costs, but I found some out in my shed, it's cheap though. In addition to these you will need a bucket or two, a sponge or bug scrubber, and some soap, as well as a wire brush.

Step 2: Get a Garage to Weld Your Rust

If, like myself, your vehicle is older, then it may have some holes or severe rust. Take these to a local garage or welder, and they will be able to weld a plate after they remove the bad metal. This can be pricey, so shop around, I had quotes of 150 +VAT at first, but found somebody to do it for 40. If you know a guy, then it may only cost you a few pints !

Once it is welded, they may cover it for you. My garage painted it in similar stuff to the hammerite, so it blended right in, but they only painted the welded area so the rest needed sorted.

Step 3: Thoroughly Clean !!!

The next step is really boring but very very VERY important. You need to get a damp sponge, or even better a sponge with netting over it, often called a bug scrubber. Wash the sills down with some form of detergent. I used washing up liquid, just because it was around. make sure you scrub as much dirt off as is physically possible. Anything left will contaminate the paint and could cause it to rust from beneath.

Step 4: Brush Off Loose Rust and Paint

This is also very important. Get a wire brush, and brush off the paint flakes and any small patches of rust. All around the spot welds were covered in little spots of rust, which was actually more than expected when the paint was flaked off, as is always the case with the dreaded R word ! After this, wipe any rust dust off with a rag then make sure everything is thoroughly dry. It could be left in the sun for a little while, but I cheated and gave it a blast with a hair dryer for 5 minutes or so.

Step 5: Mask Off the Area to Be Painted

This is an awkward stage but take care. Make sure the profile of your tape is smooth, and that all the bits of tape join together smoothly. In corners make sure the tape is not stretched, as it will peel off during painting and leave you with a small defect from your perfect line, which is very disappointing (yes, I learned from experience :/ ). You want to mask off all areas of plastic, such as trim and mudguards or wheel arches etc, as well as a top line to where you will paint. This should be at a clean break in the bodywork. I used the curve where my doors sit, so that when the doors are closed, you cannot see the edge to which i have painted. I found this worked well and looked pretty good, but I would advise to just experiment and take your time, after all, it will look neater if you take care.

Step 6: Paint :D

Now for the fun part. once everything is sorted and masked, crack open the top of your shiny new tin of paint. You will be sadly disappointed by the look of this paint as it looks just like a thick tarry mess. Which is exactly why it works so well! Grab your paint brush and get a small amount on the end of your brush. This is not like normal paint, you don't want to dip the whole brush in, just the very tip, else it gets very messy. Don't get too much, just keep going back for more when you need it. Starting at one end, start painting in small strokes. It will go on very badly at first, with loads of brush marks and areas where its so thin it just looks like brown stains. Ignore this and paint the whole sill, being careful not to go over the masking tape too far (it's there for a reason ! ). Once you have done one side, go round and prepare the other side. If the other side is already prepped, just paint away. Remember to keep all brush strokes in the same direction though, or the finish will be rough.

Step 7: Keep Painting !

You will need to build up two or three thin coats. Some areas may even need more, which you can just build up when you notice them. Between each layer allow about 15 minutes to half an hour, just so the surface of the paint can cure and harden, allowing the next layer to go on easily. If you leave it too soon, then when you put another layer on, the one underneath will move off and you will be left with the same thickness of paints with the same defects, which was what you tried to remove by applying more.

Step 8: Remove Masking Tape

This is a slow process, and one where you must be very careful. starting from one end, Slowly peel the masking tape, so that you pull the bottom edge up away from the paintwork. This will leave a crisp edge. If you pull the top edge of the masking tape down, then the paint may peel off with the tape slightly, leaving a rough edge. work your way along, until one side is unmasked and looking mighty pretty. Do the same with the other side. DO NOT PUT PRESSURE ON THE FRESH PAINT !!! Try your hardest to keep your hands from resting on the fresh paint, as it will be soft and it's a pain to repaint once you remove the tape (again, learning the hard way, sausage fingers on fresh paint leave nasty marks that just aint up to my standards ! ). Once removed, allow to dry for a bit, and then take a look at your tidy new paintwork. It will still be tacky, as this paint never dries completely, but it will not rub off on your clothes unless you lean against it hard. This makes sure that any stonechips don't damage it, unlike factory paint that is applied.

Try to leave it for as long as possible before you drive away, as it is still soft and can easily be chipped or scratched before it is fully cured. I learned this the hard way and went out for a drive 3 or 4 hours after I finished, and came back with 2 little chips, which I will have to repaint in the morning.

Step 9: You're Done !

Now is time to sit back and relax, knowing that your sills will stay rust free for a little longer, and all for under 30 quid ! If you want you can paint your wheel arches, fuel tank, chassis, and any other low hanging none moving/working/hot parts. Keep this paint away from engine blocks and exhaust systems, and definitely steer clear of brakes ! Have fun doing it, and your vehicle will thank you for it, as will your wallet !

Cheers guys for reading my instructable, I hope you enjoyed it, feel free to give me any advice or tips. I am not a mechanic, I am an Engineering student, so this may be different to whats done in garages, but it worked fine for me and only took half a day.