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MG Midget and Sprite Technical - Bodyshell rust and past treatment

Hi all :)

Long time not disturbing you :)

As the spring is back (for good this time?), the midget (1275cc 1972) take back "weekend duties" for some time :) I was making checks and preventive maintenance, and the "rust" start to disturb me more and more...

When I bought the car, the previous owner told me that the car has been "worked on" and resprayed in early 2000. When I go under the car, and in the wheel arch, it looks like there is a "black paint" on top of the yellow paint, which is really crusty. It does peel off in a lot of places, and I wonder what to do with that...

- Is it a treatment to protect rust, that was badly applied? What kind of treatment?
- Should I leave it like this? Remove it (I wonder if doesn't keep moisture, rather than protecting the car
- How worry should I be?

I am aware that the bodyshell will need some care at some point, but I don't have the space to do a bare protection at the moment, and for the next few years...






CH Hamon

In some areas, I also have a sort of "mastic", really soft and foldable/malleable where panels meet together. I guess it is also an attempt to protect from rust... Do you have the same? Is this good or bad practice?

To my small understanding and knowledge, rust treatment is great if well done; more dangerous than anything if not done well (keep moisture in...)

Except from that, I am still impressed by how robust those cars are with "a bit" of care (and a lot of love :p) :)


CH Hamon

Cedric

It looks like rubberised underseal to me - useless imv. Looks great when freshly applied but hides rust and tends to detach from the metal and traps moisture, hence the rust continues. If it were mine I'd scrape it off then wire brush (manually or with a drill) and see if you get to bright metal. If holes start appearing, that's a problem and, ideally, the wheel arch(es) might need repair sections welding in. Then, if it were mine, I'd put something like chassis black or rustoleum combicolor on by brush or roller. It'll take a while but, unless there are still substantial bright, shiny areas there's no point just applying underseal here and there (unless you're selling.....).
Bill Bretherton

Cedric,
Likely your car has old bitumen underseal which dries out and let’s water beneath and rust.

Where you have shown that edge seal strip coming off, it was a sort of preformed seam sealer and debonds and peels off - rubbish best removed.

Best to remove anything that is loose with a scraper or old wood chisel and abrade to remove as much surface rust as possible.
If you can I would apply a rust converter to bare rusted areas (Hydrate 80) followed by an epoxy mastic paint.
When fully cured apply a wax based underbody seal.

I use Bilt Hamber materials as I am impressed with them and so are my mates who use them on their Clasisics and boats.
Very helpful if you phone as well.

If you want a quicker fix for now I would do the prep and apply the wax underbody sealer - brush or aerosol which are large industrial sized ones. Better than letting it rust !

R.

richard b

Thanks a lot for your views, they make sense and I fully agree with :)

This car keeps me busy :p
CH Hamon

This thread was discussed between 28/05/2021 and 30/05/2021

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