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topic 24718

Preventing electro galvanic reaction between aluminum and steel


Can somebody please advise me on how to prevent the electro reaction between mild steel structures and aluminum components mounted onto such structures?

Your advise will be greatly appreciated.


Galvanic Corrosion



What is corroding, the steel or the Aluminum? Aluminum will protect Steel locally. If the steel corrodes, pretreat and paint (or galvanize)it before assembling the Al fixtures, and use the correct nuts and bolts. If the Al corrodes (as well), you are probably working in a marine environment. Avoid cast Al and anodize or chromate and paint the fixtures. Anyhow, putting an electric insulator between the structures and fixtures could only improve the situation.

Good Luck,

Peter Piessens
- Bertem, Belgium

February 19, 2010

Hi There

I will be fitting an aluminium downpipe 0.8 mm thick to a mild steel gutter 2.0 mm thick and would like to know if either one will react negatively. I was planning to put in rubber sock over the steel spigot will this help?

Mark Boggon
sales manager "gutters" - Cape Town

Rainwater Harvesting

February , 2010

Hi, Mark. Galvanic corrosion cannot occur unless there is actual metal-to-metal contact because you need a flow of electrons for it to happen and electrons flow only through metal, not through liquids. So, if your rubber sock prevents metal-to-metal contact, you are fine.


Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

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