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Rust Guide

Ax's are all getting on now and with plenty heading to the scrapyard with terminal rust if you want to keep yours on the road its something you really need to keep on top of. There is nobody that can ignore this guide. If you think your ax is totally rust free, keep reading.. i bet its not.

Some simple facts about rust

  • Surface rust Its only surface rust till you poke it with a screwdriver, then its a hole. Every day you leave surface rust the worst it gets. Do not think its OK to leave it as “its only surface rust”
  • It doesn't slow down Once its there its going to carry on progressing, the longer you leave it the more work it is to fix
  • You can't see it all A few rust spores under the paint, or just a slight bubble might not seem so bad.. but once you start to clean it up its pretty much always a different story. Sometimes the rust is coming from the other side of the panel and its way worse than you can imagine.
  • Dont let it rust because you dont want to have to pay for paint A lot of people don't bother fixing the rust because they don't want to respray a panel. All your doing is making more work for yourself, fix the rust then just give the panel a quick spray with an aerosol. It might not be pretty but it will look better than a rusty hole.

Common Areas

Well the simple answer is everywhere really. There are a few common places that ill list here but rust can form anywhere, it only takes a stone chip or a previous body repair to let rust appearer in a strange place. Ill start from the front of the car

  • Behind the front headlights This is the most commonly known, because its an mot failure!

Starting to go! This needed a small plate welding in.. which is better than a big plate.

Big plates can be useful too…

  • Wing Mounting Its supposed to hold the wing on, but often rusts away.


That rusty lump of metal still attached to the wing is supposed to be part of the bodyshell.. oops!

Taken from the underside of the car looking up. Showing wing mount just about attached. The hole you see is the same hole you would see when looking under the bonnet behind the headlight just from the other side.

  • Anywhere around the battery tray Leaking battery acid = :(
  • Chassis leg seam Great shape for promoting rust, cheers Citroen.
  • In the scuttle panel Seems to be hit and miss this one, and its awkward to view when buying a car cause the panel covers it. Its also a pig to get at to fix if its progressed quite far!

Taken looking down into the scuttle tray (having removed the plastic panel between the windscreen and bonnet.

  • Windscreen Around the windscreen at the top can start to rust. Its usually not that bad but can be a screen out job to sort properly. Most ax's could benefit from a new screen now anyway as they go milky at the bottom due to delamination.


Also a bit of rust developing in the gutter, with a bit of clever masking this is an easy fix and could be sorted in well under an hour imo.

  • Door sill Caused by the seat belt or shoes chipping the paint


This needed welding, was probably caused by a small chip a good few years ago.

  • Door bolt (Where the catch latches onto) Stress causes the paint to crack and let rust progress

  • Under the rear seats Ooh look, a hole! Another mot failure as its close to the rear beam, can sometimes be missed by the mot man though.

A nice hole, Easy to repair really so should be sorted asap. It is well within 30cm of the beam mounting point so a 100% mot fail!

  • Spots of rust below the window Ugh, an ugly one. This is usually caused by condensation from the inside once its progressed far enough to show up on the outside its quite bad already.


Doesnt look that bad does it? Most of it was covered by the window and the window rubber. People would probably try pass it off as “surface rust”


This is the other side of the panel

  • Rear of the sill Well in fact the whole sill, but ive found its more prone going at the rear.
  • Rear 1/4 panel Usually caused by chips or salt off the road sitting behind the bumper bar bracket, you need to remove the kit and bumper to assess how bad the damage is


It may look like this, or just a small bubble under the paint.


Cut the panel away and you can see the rust progressing on the inner panel that you can see behind the rear light


In severe cases this panel rots away totally, its sandwiched between the inner panel and the outer panel so is tricky to get access to weld new metal in. It may be hard to see in the photo, its taken from where the rear light would be and you can see the panel is missing so you can see the tyre.

Also cars with an arch kit can have problems with rust under the bodykit. Out of sight out of mind, until the arch falls off! This is the reason i would never bond a body-kit to a car as it cant be removed to inspect!


Maybe next weekend you need to take your arches off and check for any rust….

  • The boot floor Rust progresses well under the seam sealant before it becomes visible. If your car has sound deadening this can quite often take the place of metal in the boot.


Once its been attacked with a needle gun


A bad example!! This is after some small prodding, you can see its not only gone in the boot floor but higher up too. This couldnt get much worse right?


Wrong! The sound deadening and paint was covering up even more rust

So that's the common areas to look at, some are easy to check, others not so, but its worth doing.

Fixing it

First job is to assess how badly its rusted. This involves cleaning it up. Get a screwdriver and give it all a really good prod. Rust has zero structural strength so there's no point leaving it there, if it can be peeled off with a screwdriver or knocked through then do it. Rubbing it with a hard wire brush will help to remove any dead metal.



You can get these sorts of brushes that go onto drills or grinders and go on at different angles. Very useful to have but sometimes are just too bulky to get in the tighter spots.

So now you've got a rusty hole with a screwdriver stuck through it, and it looks alot more rusty than it did before. Good. For those who have no welding experience this is where you need to call in some help, the rusty metal needs cutting out till you get some fresh metal. A new bit of metal welding in then some body filler to get it nice again.


Heres an example of some metal thats been replaced and new stuff spot welded in.

If your screwdriver didn't go through, you need to properly clean the metal. Something like a wire brush, a grinder with a wire wheel or grinding stone .. or if you have a compressor a sandblasting gun is best for the job. Note: if your sandblasting its apprently best to clean the metal with thinners first, the por-15 guide says you can force contaminates into the metal sandblasting so cleaning helps to avoid this - im not too convinced myself!

Your aim is to get down to clean shiny metal, rust is like a parasite so you want it all gone or it will just come back.

Ok, time for me to introduce the first product of a few that can help. Kurust is produced by hammerite, its available from most car places. Halfords being one of them. RRP is about £6-£7 a tub. Note: don't use this stuff with POR-15


Kurust is supposed to work by neutralising the rust, they make some pretty bold claims of which I personally think are quite extreme. This isn't a wonder product you can paint on a rusty item for a cure as it doesn't seem to penetrate very deep. However once you've cleaned your rust up it is useful to give it a quick coating of this stuff. It can also be useful to get to areas you cant easily clean up with other tools.

Carrying on, im going to assume were dealing with a panel that you can get to the back of. It goes without saying that you need to treat both sides of the metal, but its surprising how many people “forget” (aka get lazy). If you cant get to it then its tricky, if you can get any Kurust down there it should help, so will waxoil (see prevention).

So basically its a few simple steps – Clean the metal, repair as required, treat, paint.

Before I get into my personal project im just going to make a quick note, condensation is a problem with ax's on the rear window. Get some kurust, paint, then waxoyl (or even normal oil) and try get as much as you can in the seam round the window. Its tricky to get at, you will need to remove the rear seatbelt mech, rear light, rear speaker pocket and the window rubber for best access but if you can prevent rust here its a real life saver as its a nightmare to fix. If you can get a waxoyl gun with a hose on so it reaches further round the window frame you should get good results.

So now a case study, using my own car im hoping will last a long time. I've done my research, and ive decided on some products that are supposed to be the best for repairing and preventing rust. It might not be what everybody agrees with but its got a lot of good reviews over the intarweb.

The products called POR-15 (it stands for paint on rust btw) They have a range of products focused around their POR-15 paint. This isn't your usual hammerite, nor is it priced like it.

A few mildly interesting facts about POR-15

  • It needs special thinners if you want to spray it
  • It dries hard but remains flexible
  • It is 100% NON porous (that's how it prevents the rust, no air can get to the metal)
  • It dries so hard, if you spill some on the lid and put the lid back on, in a few hours you wont be able to get the lid off without cutting it off
  • If you dont prep the panel properly, the por-15 will peel off like a giant mould of the panel
  • Moisture makes it harder!
  • It can be painted over, painted with a brush or sprayed
  • If you get it on your body it wont come off until your skin sheds a few days later
  • It sticks to rusted surfaces better than new metal

Keeping in mind where they're prone to rusting… my plan is as follows

  • Spray the engine bay with por-15, primer, then body colour paint
  • Spray the underside of the boot floor, behind the rear lights, wheel arches with por-15 and then a underseal like topcoat (again from por-15) I bought a chassis painting kit which contained both paints and cost around £30

My shopping list was as follows:

  • Marine Clean (946ml, US Quart) £7.66
  • POR 15 Rust Prevention Paint (473ml) £14.89
  • Metal Ready (946ml, US Quart) £11.91
  • POR-15 Solvent (946ml) (thinners) £8.94 (only really required of spraying it and not brushing it)
  • Chassis Painting Kit £25.53

Total £79.27 INC VAT

Note : Chassis Painting kit = 3x 118mm cans of por-15 and 3x 118mm cans of chassis coat black. Note2 : You only thin por-15 by 5% max so you dont need much of the solvent

Marine Clean removes contaminates from metals

Metal Ready is similar ish to Kurust except it doesn't neutralize the rust. It is brushed or sprayed on then washed off leaving a protective zinc coating.. its important to use this or the por-15 wont stick properly.

Items were purchased from

The theory behind all this is, that if you put a coat of paint on that's so tough and non porous so that nothing can get to the metal, rust cannot start nor progress any further.

Always follow the instructions for each product to the letter for best results.

FIXME This storys still ongoing, I shall update this guide with pictures and further info once ive put the paint on the car!


Prevention is better than a cure

Once you've removed all the rust and repainted the area you need to find some way of preventing the rust. Its easy to do and really does make the world of difference

  • Keep it clean Clean away any leaves and mud from the body, especailly in the wheel arches. These are great for holding in the moisture and acclerating rust.
  • Keep checking Check over the car for any rust thats starting, treating it when its just starting out is an easy job compared to leaving it.. dont put it off till another day!
  • Waxoyl!!! This stuff is the daddy of rust prevention, i cannot stress how important this step is and it needs to be repeated every year or so. Its cheap and makes a massive massive difference to rust. For those blessed with a compressor get a proper waxoil gun, heat up the oil with a blowlamp and try get it as far down the sills etc as possible. Be warned that the car will drip out waxoil for a few days after so dont park it on your nice block paved drive. For those that aint get an oil can and a brush and try get it as far down as many awquard places a possible, Inside the sills.. around the rear window as a i mentioned before. Inside the doors etc..etc..etc!!!



Example waxoil gun. Heating up the oil makes it thinner so it runs into gaps better

Further Reading website UK POR-15 Retailer

rust_guide.txt · Last modified: 2016/08/18 20:27 (external edit)