Removing rust and painting over

[RR76]

I thought I'd try and fix some rust spots under the car, do you need to remove every spot of rust to the bare metal before you paint over it, would painting over a thin layer of rust be useless?

How do you do it?

[996Type]

Depending on the size of the areas involved, you have a few options.

If you can and the weather is warm, a few days before blast the underside of the car with a pressure washer to remove as much surface rust as possible.

If you have covers (inner wings etc) remove those and clean any loose material from behind them. Allow everything to dry and drive the car to eradicate the last of the water.

Next remove any loose rust via wire brushes / sandpaper / abrasive tools.

Get as close to bare metal as you can then liberally paint on “rust converter” which will convert the chemical composition of rust into a solid surface.

Then paint the areas in something like POR15 which provides a rock hard coating over the treated area or a good quality chassis paint.

Finally, douse the area in Bilt Hamber wax under seal and you are good to go.

I’d avoid plastic type under seal as these can create water traps when they break down. If you keep on top of the above you can do an annual inspection and just top up any areas that are coming back through.

Based on the condition / size of the area involved you can also use one of the several garages up and down the country to do this for you (many specialise in protecting 4x4’s), treatment is around £600 and they will need the car for a few days to do it properly.

Based on the condition of the rust, do you need any welding as this will need adding on.


https://bilthamber.com/product/hydrate-80/

https://bilthamber.com/product/dynax-ub/

https://www.rust.co.uk/product/cat/our-complete-ru...

[steveo3002]

a scrape down and painted with zinc primer /epoxy will be better than nothing and prolong its life , the cleaner you can get it the better it will last , but yeah seal it away from air and moisture and the rust will slow down alot

[Bainbridge]

I'd do a bit of research on your particular car before starting underbody rust work. If the car is prone to rusting from the inside out via the cavities, then you'll need to get these done too.

It would be heartbreaking to spend a lot of time and effort underneath only for rust to appear from the inside.

[Belle427]

Rub down with a wire brush first and apply something like this, ive used some recently and am quite impressed with it.

https://www.rust.co.uk/shop/diy-vehicle-restoratio...