[Petrol]

Originally Posted by Petrol

I did quite a big write up on rust removal / prevention. I will dig it out for you.

First of all I have no experience with rust "killing" primers or paint on rust products. There are loads available – POR-15, Finnagans No.1 and Hammerite smooth are some that spring to mind. I also have very little experience with rust converters, these products are applied to rust and "stabilise" it ready for primer, Kurust is an example.
The reason I have not tended to use these products is that you are relying on the product to stop the rust, if it doesn’t do the job due to it being a poor product or poor preparation / application then it’s all been a waste of time. When metal rusts, it goes porous and forms layers. One of my biggest concerns with these types of products is getting the product to penetrate to the very bottom of any pitting. If the product is quite thick then it will just form a skin on top. Oxygen is required for corrosion to occur so if a paint film is applied over the top, it will continue to corrode as oxygen will still be present. Another preparation concern is oil or grease, if there’s any of this evident then the product will not do its job. I have always gone for mechanical or chemical removal for these reasons.

Shotblasting is the best way to remove rust, it’s quick but the only drawback is the blast media gets everywhere. Done right it will remove all rust and leave a very slightly pitted finish offering a good key for primer. Wire brushes also work well but what you must remember it can be difficult to get all the rust out of the pitting, softer brushes with thin bristles can be useful for this. Twisted knotted wire brushes used in angle grinders are to stiff. One drawback with wire brushes it that the brush gets contaminated with microscopic rust particles so you are spreading these particles over the area as you are working.
I have only tried 1 brand of chemical rust remover – Deox from Bilt Hamber. They have 2 products, Deox C which makes up a solution for parts to be dipped and Deox Gel. The Gel can be used to spot treat areas underneath the shell or areas impossible to get to with a wire brush. It does however take time. Once applied it needs covering with cling film to prevent it drying out and ideally needs leaving 48 hours. It’s then got to be scrubbed with Scotchbright before being washed off and dried as quickly as possible. I have had to re apply it up to 3 times in certain circumstances. It does work though.


What do I apply under the arches/floorpan?
The best rule of thumb is to replicate manufacturer’s methods – Stonechip under the arches and wax in box sections.
Bare shells are dipped in electrocoat at the factory, this is obviously not an option for DIY but the next best thing I have found to apply to bare metal is a zinc rich primer. Unlike conventional primers which are porous, a zinc primer will protect the steel from corrosion. This can be applied by brush or spray. For maximum protection 2 coats of 2K epoxy paint should be applied over the primer which again can be applied by brush or spray. Please be aware however that 2K products are hazardous and it’s essential to use a mask. As an alternative, a chassis black 1K product could be used. Stonechip should then be sprayed on top. I don’t recommend brushing it on but aerosols are available from your local bodyshop supplier.
I don’t recommend spraying wax products over the top of stonechip, it will soften the stonechip reducing its effectiveness. Dirt and salt will also stick to it.

My thoughts on Waxoyl
Inside the sills is factory coated with a rustproofing wax. It’s a very thin coat and has a smooth finish. Any water that enters the cavity will naturally run down and out of the drain holes.
The problem with applying Waxoyl is achieving this perfect finish inside the box section. What you typically end up with is a very rippled finish. I believe that this causes water to puddle in the Waxoyl. The problem being that this water evaporates and since there is very little or no ventilation inside the sills it has no where to go other than condense inside. I have also found that spraying Waxoyl on rust does not "kill" it, it just corrodes behind the Waxoyl.



Hope this info is useful