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MG MGB Technical - Acid bath - yes or no?

Opinions are divided about the advantages and disadvantages of using an acid bath to clean the entire monocoque before a rebuild, versus sand blasting or just good old scraping and wire brushing.

Obviously it is easy and fast, but I notice some are worried that the acid is difficult to neutralize properly where parts are spot welded etc.

What are your experiences and opinions?


I have looked into this recently in preparation for my next project.

The way in which it is done and the rinse and neutralising processes are important. They have to be more effective at getting the "acid" out than it is at getting in. The firms who are properly set up to do this don't just use of the shelf "acid" but modified acids taylored to this application. I will email you the information I have.

For smaller parts, such as the heater enclosure, I have stripped and derusted at home. The paint and dirt were removed by light scrubbing after an over night soak in caustic soda. (1500g of caustic soda crystals to 10 litre of water). The rust then removed by electrolitic process, again over night. Low noise and low use of my time.

David Witham

I have done it and am a big fan of the process. I figure the car is going to be in epoxy primer for a year or two before I paint it, so any trouble spots are going to be detected by then. As to the head start it gives you by having al the little bits and bobs clean and ready for paint in one go, it can not be beat. Sandblasting will never get as much rust out as chemical dip. Much cheaper than blasting as blasting is a time based cost and chemical dip tends to be done by the pound.

I blasted my GT and still find sand 20 odd years later!



It really depends on the experience and quality of the firm doing the acid / chemical dip.

Anyone can put a stripped shell into a chemical bath but the process continues after the shell is removed and it is essential ALL traces of the chemical are neutralised otherwise it continues to corrode unitl it is entirely consumed or there is no metal left for it to act on.

There final step is painting the treated shell and at the factory it was also dipped to ensure the primer and paint coats were able to penetrate every crevice and pocket of the completed body.
This may not be able to be done by normal spray means and some areas may be unable to be treated which leaves areas for rust to begin.

My suggestion is you will get what you are willing to pay for and any place offering a quick and cheap job will probably deliver exactly that.

Perhaps contacting some of the race and rally organisations locally to get some recommendations would be worthwhile. Race and Rally teams often use this process to clean shells prior to them being seam welded and other specialist equipment being installed.

Hope this is of some help.

Cheers , Pete.
Peter Thomas

Thanks for your comments. After reading them and the very interesting info I got from David, I think it is right that it depends on the competence of the firm doing the job. I am not quite convinced that my local "acid dipper" is doing the cleaning and neutralizing properly, and will have a closer look.

The car in question is my midget project, with very little rust, but a lot of paint and underseal!


David,I would like to see the emailed material that you collected/data. I plan to get my MGB dipped this next summer.Thanks,Rich Osterhout
Rich Osterhout

This thread was discussed between 23/06/2006 and 26/06/2006

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