Cleaning Metal

[danchip]

I've got some cast iron ornaments which have previously been kept in place with bitumen, I would like to clean all the bitumen off but have tried chipping it off, scraping it, burning it off but all of these are making a bit of a mess of them.

A work colleague has suggested dipping them in acid like you do with furniture.

Could anyone advise if this would work and what sort of acid would do the job

[TWR]

Petrol / Paraffin, white spirit,

[tonyav]

Acid would attack the metal but probably wouldn't do much to the bitumen. Have you tried soaking them in turps or White spirit.

[TonyV]

I don't know of any acid that will react with bitumen. If it is bitumen it should burn, albeit with acrid black smoke. Are you sure it is bitumen?

[danchip]

Definately is bitumen, when ive tried burning it the bitumen melts which is fine but it discolours the iron.

Would nitromors work?

[tonyav]

Give it a try, danchip.

[TonyV]

Ok it may be easier to melt bitumen and then wire brush on metal to get rid of discolouration or as TWR suggests try a solvent - my hunch is that paraffin may be best bet

[carrust]

Creosote softens bitumen, then soak it in white spirit, then give it a good soaking in washing up liquid. Finally wash in warm water.

[tonyav]

Don't think you can get creosote these days, rusty.

[carrust]

Oh yes you can tony.

[tonyav]

Thought it was banned.

[carrust]

You could also throw the metal into the embers of a bonfire. I've done this with a garden gate...it works a treat.

[TonyV]

I thought creosote was deemed carcinogenic and therefore not on sale as such. Another thought is to try some diesel.

[beegeebee]

Brake fluid and engine oil seem to work. Just look at house drives where the stone of the macadam is showing in places.

[EDDIE51]

As said do NOT use acid it will corrode the metal but have effect on the bitumen. A bit of a long shot, but as a chemist/metallurgist I know this would work , heat them to around 600 C in a vacuum furnace. That turns all the bitumen to Carbon Dioxide while the absence of air (vacuum) would prevent any tarnishing, they would come out looking like new and shiny clean. If there is a metallurgy treatment company near you they would do it and it should not cost too much. It would take an hour or two furnace time.

[EDDIE51]

Sorry 1st line typo.>> but have No effect on the bitumen!

[MichaelZZ]

How about shot blasting?
Depends where you live but if it's anywhere in or near an industrial area yu could google "Local shotblasters" and ask them for a price.