Does copper/aluminum/stainless create a galvanic corrosion problem?

Hi,

I'm building some 12V DC replacement starting circuits for motorcycles and want to make sure I am not creating problems with galvanic corrosion. I've read through some sites and the wikipedia entries but I'm still not clear.

Here are my situations;

1) I have tinned solid copper terminals that go on top of a steel terminal that cannot be removed from the bike loom. Both of the terminals mount on the lead poles of the battery. To create a copper to copper path I supply copper bolts/washers and nuts/ So the path is the lead battery post through copper and steel to my copper terminal. On some newer design batteries they now come with brass terminals.

I don't see any issue with the above but would appreciate any tips/advice/comments.

2) I have a solid copper terminal that is bolted down to a hole threaded in the aluminum engine case. The motorcycles come with mild steel fasteners which corrode and the allen holes in the fasteners strip out. So I have been supplying a stainless steel replacment bolt and washer. I also supply a small quantity of anti-seize for the threads.

I wonder if the stainless/copper/aluminum creates a problem.

On both of the above up to 60 amps flow during engine starting.

All comments and replies are appreciated.

Michael Heth

It's not a problem if there's no moisture...but this is a motorcycle.

Stainless steel in it's passivated form (which is the stuff at the surface that makes it corrosion resistant in the first place, beneath that is active form) is really bad at this with most metals because it's so noble and will cause other less noble metals to corrode away:
https://www.corrosion-doctors.org/Definitions/galvanic-series.htm

It's not a big deal if you have a little bit of stainless steel and a lot of copper/aluminum. But if you have a lot of stainless steel and a little bit of copper/aluminum, then it's a problem. So a stainless steel screw in a block of copper/aluminum is not a big deal, but a copper or aluminum ring terminal against a stainless steel block is.

Also stainless steel is more resistive than mild steel.