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#3658 01/23/2003 12:38 AM | Joined: Jul 2000 Posts: 962 Shop Shark | | Shop Shark Joined: Jul 2000 Posts: 962 | Ok, those with some electrical or metallurgical knowledge may be able to answer this for me. As you know, when you screw a piece of cast iron to a piece of brass in the presence of water, you form a very small battery. The dissimilar metals form a current due to electron flow from the iron to the brass. This galvanic corrosion will oxidize the cast iron.
The reason I ask, is I had cast iron elbows screwed into my water pump & thermostat housing. A brass hose barb was screwed into each elbow to bring water to & from my heated manifold. Well, when I took my old engine apart, I found corrosion in the iron elbows, and a little corrosion in the thermostat housing and water pump. Those fittings were installed less than a year previous.
How serious is galvanic corrosion in the presence of ethelyne glycol antifreeze? Should I try to find nipples made out of iron, or what? I'm afraid of causing some sort of cooling system damage due to this. Is it just caused by the grey iron elbows? Would screwing brass fittings directly into the water pump and thermostat housing cause the same issues?
thoughts?
chip
Preaching the Hot Rod Gospel according to the 4-stroke apostles:
Suck, Squish, Fire and Fumes
| | | | | Joined: Oct 2001 Posts: 3,458 Extreme Gabster | | Extreme Gabster Joined: Oct 2001 Posts: 3,458 | Well, all of the temperature sending units use brass fittings with no problems. It may be that the corrosion of the iron is normal or caused by cavitation from the water pump. Try a bit of teflon tape on the threads, maybe that would help? Or you could switch to brass elbows.
Paint & Body Shop moderator
A lone amateur built the Ark. A large group of professionals built the Titanic. | | | | | Joined: Jun 2000 Posts: 2,773 'Bolter | | 'Bolter Joined: Jun 2000 Posts: 2,773 | If you're running fresh coolant at a 50% mixture year round you shouldn't be having any galvanic problems. I don't know just what buffers are added to the a/f to prevent galvanic corrosion, just that there are supposed to be some. This is also an area where the name brand a/f is preferred over the knock-offs, additives are supposed to be better, but I've never actually seen proof.
Fred
52 3600
69 C-10
| | | | | Joined: Sep 2000 Posts: 67 Wrench Fetcher | | Wrench Fetcher Joined: Sep 2000 Posts: 67 | The same thing happens with any two dissimilar metals, like an aluminum intake on iron heads. With time it is possible to corrode things to the point where they are ruined. One way to fight it is placing a piece of reactive metal such as zinc or magnesium (I can't remember for sure) in the coolant. I seem to remember a company a few years ago that had a special radiator cap that had a piece of one of these metals attached to it. The idea is that the metal acts as a sacrificial anode and it corrodes instead of your engine parts. It might be worth looking into.
Aaron | | |
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