Learning How To Do Rust Repair!

Many old cars suffer from rust, or cancer of the metal as I like to call it. Not only does it look horrible but the metal it is on weakens as it corrodes which can cause holes in places to don’t want holes! Chrysler era Mercedes of the early 1990’s to early 2000’s are particularly prone to rust as, basically, Mercedes accountants were penny pinching with the materials they were using. My W202 C-Class is sadly no exception to this rule.


I had been offered to get the car painted at a good price but sadly it didn’t come to be. I could get the rust repaired elsewhere but it costs a fair bit and I would rather save that money to get the full car done to a show standard at a later date.

Bodywork isn’t a job that you can go into lightly. It’s best to do your research and get as many materials as you can. If you don’t take the appropriate preparation you can make your car look even first.

The first thing you will want to do is take the rust back to bare metal. It bubbles up and gives an uneven surface so you will want to sand it back as best as you can. For this I will use sanding discs for a drill to take off the majority of the rust and sanding blocks to just to pick off any remains.

Be sure to sand back the paint around the afflicted area too. Just to make sure that you have got all he rust out. It wouldn’t be fun to treat an arch then have to go back and do it again a couple of months later because you missed a spot that is now growing.


Please note these pics were taken in the middle of sanding. I know there are still some high bits and they were taken out by hand! 🙂

You would have also noticed that I’ve taken the wheel off too! This is partly to prevent any sort of accident involving my drill going through my tyre and partly to allow me access to the wheel arch to spray on some Waxoyl. Wonderful stuff which makes your wheel wells look tidy and black and protects against corrosion.

The next step for me was to apply some Hammerite Kurust. Kurust converts rusty metal into a stable sandable surface. I’m using it more to protect against future corrosion and will be using a filler over the top of it to get the shape of the arch back.


It comes out of the bottle as a white liquid which you brush on quite liberally…


…Which then dries a dark purple in colour. It’s best to leave it a couple of hours to fully dry before doing anything else to it.


The next bit is the hardest. Filler.

Filler is basically a paste that you use to rebuild the shape of the panel that you are repairing. It comes as two parts; the filler itself and a hardening compound. The ratio of this should be about 50:1, so if you are using a golf ball sized about of filler you should be using a pea sized amount of hardener.


Your best bet is to only do a little at a time and keep sanding. The more you put on the more sanding you will have to do as the filler will be thicker than the paint line. Remember you are trying to get it to the same level. I don’t know how many times I put it on, sanded it back, put it on, sanded back until I was happy with it. I found this bit difficult and it took ages!


Now to put the primer on! Now I’ll admit a mistake here so you don’t have to make it. I did my primer twice as the way I had it masked above, with the masking tape flat against the surface, left a visible step which looked awful. So I had to sand it back and do it again! The way to do it is to fold the masking tape at the edges under it self so it leaves a bit of a gap between the panel and the tape. This will protect it from most of the paint but will allow a dusting to get underneath it so you don’t get that harsh step.


As with any painting it is best to spray primer from a distance and do a couple of light coats rather than one thick coat. Hold the can level and at a consistent distance from what you are spraying.

Now for the top coat!! Again, nice and light and even spraying will get you the best results.

Once your top coat is on and dry pull back the mask. Sometimes you will get a slight step in the paint but this can often be taken down with a strong rubbing compound or, if you are braving, wet sanding with 1500 grit. I prefer the rubbing compound haha!


You may still see a very slight colour variation in these pics. I have since given the car a good bath, to get rid of the sanding dust (it gets everywhere!) and a polish and it is looking smart again!

Obviously it isn’t perfect. I have done this just to smarten the car up for the time being until it can be done properly. Bodywork is something I want to learn though and it is pointless saying you are going to get good at something if you never practise. If you have the money I would always recommend getting it done professionally but as I said I am saving up to get the whole body done to show standard. (hopefully I will be able to take you for that journey too when it happens)

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