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Galvanic Reaction


Mark Gregory

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I have a 1931 Reo Royale chrome nickel engine block . There is a copper water distribution tube that bolts to the block . What type of bolt material should I use . The machine bolt size is 1/4 diameter X 20 threads X 1/2 inch long . Brass might be too soft ? I am worried about the copper and and the bolt reacting along with the block . Thanks

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What was used originally?

If you have an electrical connection between the copper and the block, the block will corrode. Whatever bolt you use will corrode too, if you put on a copper distribution tube. Brass bolts will corrode least. Are the bolt ends exposed to water inside?

If you do use the copper, brass bolts would be best but the block will be the sacrificial anode. Very good corrosion protection will be essential, inside and out. Use a good anti-corrosive in the water and change it every 2 years. Put a release compound on the bolts or nuts if you use brass.

It would be far better for longevity to make a steel tube and use steel bolts.

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Lots of engines use steel, brass, galvanized, and aluminum components without excess corrosion problems. I would use stainless or plated hardware, and a good brand of antifreeze. Modern antifreeze will protect from corrosion, even aluminum engines. Much better than anything available before 1985.

If you are really worried you could put a hunk of zinc or zinc alloy in the rad as a sacrificial anode but it really isn't necessary.

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The material used originally was a steel distribution tube . What type of bolts I do not know . From what i can understand this water tube rusting was the downfall of this engine . As it would overheat and be scrapped because the end cylinders could not get enough water to stay cool . If the modern antifreeze will help that is great . Thanks for your responses .

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Lots of flathead engines had that type of tube. They were usually made of galvanized steel and had a life of 10 or 20 years. They also made brass ones for marine engines.

If the tube rusted away it was possible to replace it, but as you state, by that time the car was at the end of its life anyway and was usually scrapped.

With today's antifreeze the life of such a tube would be indefinite. I have taken apart 20 year old aluminum engines that never had the antifreeze changed and found NO corrosion. In the old days this would have been impossible unless the antifreeze was changed every year.

And of course, when your car was new, everyone used plain water and only put in (alcohol) antifreeze in winter. This is why old engines are full of rust silt and scale, and internal parts corrode away.

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If it was anything like my Dodge 8, every single bolt and nut in the car was cadmium plated steel. Zinc plating is cheaper and almost as good. Galvanised (or cad plated) steel for the distribution tube would be much more sensible than copper in the engine. But anti-corrosive additives are still essential because of the differing metals in there.

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