Metal interactions

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arsharpe
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Metal interactions

Postby arsharpe » Wed Feb 25, 2009 6:10 pm

Having an excess of 'G' type Berlingo batteries and am in need of a 'D' type, I am converting a G to a D using metal links and extra piping (thanks to an idea by grumpby-b). However, I have made some aluminium links and but am now concerned about the metalic interaction betwen the aluminimum and what I think it steel in the battery post and the connecting link.

Can anyone comment on metal-to-metal interaction like this ?

MalcolmB
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Postby MalcolmB » Wed Feb 25, 2009 6:39 pm

It's a long time since I put my metallurgy books away, but if I remember right the potential problem with joining aluminium to steel is galvanic corrosion. The aluminium, which is the more reactive, corrodes preferentially if the two metals are connected by an electrolyte. In other words as long as the metal/metal interface is kept dry there shouldn't be a problem. There may be very slight corrosion due to moisture in the air, and I would check the condition of the links once a year or so. It might be worth checking out the data sheet on Noalox, a compound that's designed to minimise surface corrosion and resistance in aluminium joints. If you search this site I think Greg has tried some of this for the connections on his lithium cells.

john
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ni cad links

Postby john » Wed Feb 25, 2009 7:05 pm

ALUMINIOM WILL CORRODE as THE ELECTROLITE ATTACTS ALI NICKLE
PLATED COPPER IS USED BY THE BATTERY SUPPLIERS AS LINKS
JOHN CRAYTON

MalcolmB
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Postby MalcolmB » Wed Feb 25, 2009 7:26 pm

Hmm, maybe I misunderstood the application. Are these links likely to get wet? John is right if so.

arsharpe
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Postby arsharpe » Wed Feb 25, 2009 9:56 pm

Well it shouldn't get wet unless the coolant pipes leak.
Thanks for the Noalox suggestion, as it is sacrificial anode as well it sounds.
I am pretty sure that the originals are not copper as they are very stiff and are not copper coloured under the flakey (probably nickel) coating.

john
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ni cads

Postby john » Wed Feb 25, 2009 10:27 pm

THE PROBLEM IS NOT RAINWATER BUT ELETROYLITE SEEPAGE AT THE
TERMINALS WILL DISSOLVE ALI AS IT IS HIGHLEY CAUSTIC THE STIFF LINKS ARE PROBLEY STEEL NICKLE PLATED JOHN CRAYTON

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qdos
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Postby qdos » Thu Feb 26, 2009 12:38 am

You should try to use similar metals where ever possible. Aluminium and Steel most definitely do not get on well together, it's known as bimetallic corrosion. John C is right. effectively what you've got with dissimilar metals together is a battery just and an electrolyte and hey presto. Works just the same in an alkali too. Seen it many times on offshore platforms.

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ChrisB
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Postby ChrisB » Wed Mar 04, 2009 8:40 am

Yeah I wouldnt use Ally, Large copper bars/plate is a much better option, ally will very quickly disolve due to the caustic nature of the batteries.

They "shouldnt" have any leakage as I'm sure the output terminals have a seal but would you want to risk it on a battery in the middle of the center pack of a berlingo :shock:

ChrisB
I reject reality and substitute my own !!!!!!


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