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Q&As since 1989


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Direct Current Field and Related Corrosion

I have been informed that Electro Motive Forces may corrode a aluminium boat. I have an issue of a CD player being fitted to an aluminium vessel. This requires a permanent power feed for memory of presets and player history. My work mates have suggested that a permanent power source drawing current constantly would corrode the vessel. Is there an formula to work out if this would take effect? Please note: All our vessels only run a DC 12 volt system.

Jason Goodman
Aluminium Boat Manufacturer - Gold Coast Australia
2005

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Electro Motive Force (EMF) is a technical term for voltage. In a way your friends are right and voltage can result in corrosion, BUT it is much more complex than that. For corrosion to take place, you need two different metals in contact with each other and a suitable corrosive liquid in contact with both metals. Corrosive liquids need not be acids or alkalis, as common water is pretty good at it - just look at a lump of steel left in water! I can see no reason to believe youy will suffer from corrosion if you do not allow this situation to occur. Is it possible to run the CD player on a fully isolated circuit so it doesn't use the body of the boat? If so, it may give you peace of mind.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2005