Rust killer vs Brake fluid.

[Woolly]

Hi All, I am working on a 1947 Sunbeam Talbot's brakes which has the master cylinder inconveniently under the floorboards. I know there are remote reservoir kits available to make bleeding systems like this easier, but they all seem to be plastic or fancy expensive metal, not what you would expect to see on a 78 year old car. I do have a reservoir from a later model, made of tin plate that I would like to use, but it has some surface rust inside. I am hoping someone more knowledgeable than I can suggest a way to clean the insides that won't affect the brake fluid. Any help would be greatly appreciated.
Thanks, Woolly.

Mods, please move if this is not in the appropriate area.

[Tins]

Back in the day we used wet and dry with metho. Some people prefer white spirits.

[V8Ian]

Check out POR 15.

[JDNSW]

If the surface rust is on the inside, it is going to be in contact with brake fluid. This is likely to remove a lot of coatings, so I would be very wary of using any.

As sort of suggested by Tins, I suggest mechanically removing the rust with a fine abrasive if accessibility inside makes this possible. Either metho or white spirit can be used, but all traces of hydrocarbon based material must be removed before putting it into service.

I would not coat the bare steel after removing the rust as it should not further rust provided the brake fluid water content is kept very low.

Externally, it was commonplace to paint these sheet metal reservoirs, but the paint was frequently partly removed by spilled fluid.

[Woolly]

Thanks for the replies, I’m inclined to avoid using chemicals or coatings in case they react with the fluid. One of our kids has a Dremel kit that I hope may have a suitable attachment to attack the rust inside, so I will try that next. If that doesn’t work, maybe use a plastic one painted black until I can find a good unrusty one.
Cheers, Woolly.

[Blknight.aus]

soak it in a mollasis bath for a week, keep it fully submerged then rinse it out well.

I have in the past used a strong flux and hot solder wash to seal and preserve the inside of series 2 reserviors

[Woolly]

Amongst the accumulated remains of several dead cars lurking in my garage I found a better reservoir and used that. However I tried the molasses idea on the rusty one and it appeared to convert the rust into a black substance, as well as creating an evil looking scum on the top. I rinsed it out with water, painted the outside and sloshed some brake fluid around inside it, so hopefully it will be usable if I need it in the future.
Thanks for all the suggestions,
Cheers, Woolly.

[JDNSW]

Thanks for telling us what you did in the end. This sort of thing makes the thread a lot better for anyone looking at it is search of answers to their problems.