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May 24 10 8:12 PM

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Many years ago I had an R8 and the engine needed to be rebuilt. I decided to do it properly and knew that engine reconditioners at the time used a hot caustic bath to clean oil, gunk, paint and rust from the block. So I built a fire under a cut off 44 gallon drum (yes back in imperial days) and dropped the block into the water that had 1lb of caustic soda added per gallon. (About .5 kilo per 5 litres.) After bring it to the boil and let cool. Nice clean block but the aluminium plate had gone. Recently Cyber Papy bought up the subject on another web site. This is the modern version that uses a battery charger and electrolysis to remove rust and the caustic soda will remove paint any how. The rust takes about 2 or 3 hours depending on the current applied. The paint takes over 12 hours depending on its quality. Shortly I will show a photo of my set up. Perhaps CP will translate some of his notes from the French site.

A one eyed Renault enthusiast.

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#1 [url]

May 27 10 8:14 PM

This is a 200 litre drum that I have cut to suit. Note a lid to keep the neighbours dogs from taking a drink and the grand kids from sticking their hands in. It should be on a stand, and it will as soon as the current project is finished.

Note the contents are caustic which will burn skin, note the rubber gloves.

The battery charger is 24 volt one that I had and runs at 10 amps for 50% of the time switching itself on and off to prevent overload.

There is another precaution to note, do not leave the lid on while it is operating as hydrogen gas is produced which is very explosive. Hence the report about cars that can run on water. It is true by the way. But guess why it has never been developed. Enough we are getting side tracked, perhaps for another time.

The battery charger should not be near the hydrogen gas and is only placed there to fit into the photo.

The rusted bracket was put in the solution and connected to the negative clamp, the positive clamp was connected to a piece of stainless steel. Note after 1 hour the rust is gone. Depending on the electrical current available and the amount of rust determines the time it will take.


Paint and oil will take at least 24 hours soaking but does not need the current turned on. No damage will result from leaving the item in the solution for any reasonable period as the caustic does not effect the steel, but it will dissolve aluminium.

A one eyed Renault enthusiast.

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#2 [url]

May 27 10 8:25 PM

They are in French but use Google to translate.
Scroll down each page and there are pictures that are self explanatory.

The first by Cyber Papy

Do remember safety the gas produced is explosive, the solution will burn skin and eyes.

A one eyed Renault enthusiast.

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#3 [url]

May 28 10 4:02 PM

How good is that!

Will that work with other liquids, ones that arent so nasty? Paint isn't always necessary to remove, maybe mag sulphate or the like?

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#4 [url]

May 28 10 5:24 PM

It's probably not all that nasty just that you do have to be careful of eyes and use rubber gloves. It's domestic name is "Washing Soda" a spoon full used to go into the copper with the family wash. Also a lot of heavy duty truck washs had some of the same stuff in it. I have a heavy duty cleaner and it smells the same. The hydrogen is what is already prevalent in our atmosphere and comes off batteries when ever they are being charged, like when ever you drive a car. I was just being carefull.

A one eyed Renault enthusiast.

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#5 [url]

May 28 10 11:45 PM

Thanks Flocar - I honestly do love the way this is a backyard device which works.
Old-school with caustic chemicals, hydrogen production, takes me back to my teens.
This is even better though since it actually achieves something!!

We all should have one of these!

Although I do recall many years ago I retreived my 1969 Triumph 2.5 PI block from Bryants after machining and found that all of the aluminium core plugs had disappeared. They'd caustic bathed the block, and although the waterways and galleries were immaculately clean, those aluminium screw- in external plugs into casting holes had all disappeared.
Our business (AlpinePete's & mine) had most of them in stock (amazingly) apart from only one at the front of the block which was smaller.
Amazingly again - I looked up the part on our current microfiche list and found it was available ex Melbourne.

Problem solved, and I could rebuild my engine. In those days a rarity like a MK1 Triumph PI was my actual car so I needed to use it every day.
Great car - and I can anecdotally say a trip from The Gap in Brisbane to Maleny 30 years ago could be dispensed with in under 50 minutes. Time of the day was very important!

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Triumphs x n (where n is an increasing number)

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#6 [url]

May 29 10 9:22 AM

Oh but if you have an industrial size sand blaster available, rust is not always so much of a problem.

So lucky to have those aluminium plugs in stock. Wonder if they are still available today. Yes they probably are for a Triumph. I was thinking like a Renault restorer where even normal maintenance items like radiator hoses and caliper kits are now unobtainable. Well at least in Australia.

A one eyed Renault enthusiast.

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