Avoiding Galvanic Corrosion

JMc

Solar Enthusiast
This is an interesting discussion as I’m about to strap four 280Ahr cells together. The aluminum terminals are a challenge since I don’t know the specific alloy. My anodic index cheat sheet says:

Metal / Anodic Index (V)
Galvanized Steel 1.20
Aluminum - other alloys .90 - .95
Aluminum - 2000 series .75
Tin, Tin-lead solder. .65
316 Stainless .60
18-8 Stainless .50
Bare Copper .35
Bare Silver .15

Now the rule of thumb for moderate environments says to keep the differences below ~0.25V, so:

Common, galvanized steel nuts/bolts/washers pair with the structural aluminum alloys, but not the 2000 series. Stainless fasteners pair with 2000 series aluminum, but not the structural alloys. As for copper, it had better be tin or solder plated.

I guess it’s time to find out what alloy those terminals are made of...
 

HRTKD

Boondocker
I guess it’s time to find out what alloy those terminals are made of...

My guess is that it's a lower level alloy, to provide better conductivity. 6061 is a great alloy, but not as conductive as a 4000 series alloy.

I hope you can nail down the exact alloy.
 

Hedges

I See Electromagnetic Fields!
I guess it’s time to find out what alloy those terminals are made of...

Make a battery out of it and measure the voltage?

(Piece of dissimilar metal, electrolyte, separator)

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Tinned copper would be one good busbar.
Aluminum is another.
But either way, want to get through the aluminum oxide and use a corrosion inhibitor.
 

Haugen

Tron God
This is an interesting discussion as I’m about to strap four 280Ahr cells together. The aluminum terminals are a challenge since I don’t know the specific alloy. My anodic index cheat sheet says:

Metal / Anodic Index (V)
Galvanized Steel 1.20
Aluminum - other alloys .90 - .95
Aluminum - 2000 series .75
Tin, Tin-lead solder. .65
316 Stainless .60
18-8 Stainless .50
Bare Copper .35
Bare Silver .15

Now the rule of thumb for moderate environments says to keep the differences below ~0.25V, so:

Common, galvanized steel nuts/bolts/washers pair with the structural aluminum alloys, but not the 2000 series. Stainless fasteners pair with 2000 series aluminum, but not the structural alloys. As for copper, it had better be tin or solder plated.

I guess it’s time to find out what alloy those terminals are made of...
You're better off using a noble metal chart to identify the metals that are most compatible concerning galvanic reaction.
Tge closer the metals are, the less galvanic reaction they will have when paired.
 

Volt3939

New Member
Wow, long thread!
I only got half way through, but had a few thoughts:

As far as epoxy is concerned, has anyone tried Silver Conductive Epoxy? Also available in Zinc I believe. NOT cheap!

As to flat buss bars, I believe in the belt _and_ suspenders technique, always. My CALB cells came with bars with a curve and it was recommended to strap them tightly together. It seems to me thermal expansion takes place regardless of the clamping force, so having bars with room to flex is a good thing.
 

Haugen

Tron God
As to flat buss bars, I believe in the belt _and_ suspenders technique, always. My CALB cells came with bars with a curve and it was recommended to strap them tightly together. It seems to me thermal expansion takes place regardless of the clamping force, so having bars with room to flex is a good thing.
I'm adding in high density foam 1-2mm thick between the cells to compensate for the expansion and contraction of the cells as they charge and discharge. The full range is only 0.5mm, per cell.
This means very little relative motion from one cell to another as long as they are properly compressed.
 
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