mixing bronze and s/s in plumbing

STEVE ROYER · Post by **STEVE ROYER** » Thu Dec 04, 2008 5:59 pm

I'm installing a a/c and a head in my C26 and was wondering what is the rule about mixing bronze thru hulls and s/s fittings (ball valves) does any one have any insight on the subject I was told it would be ok but would like more input .Oh the boat is going to be in salt water
Thanks Steve

EmergencyExit · Post by **EmergencyExit** » Fri Dec 05, 2008 5:35 am

Hi Steve - "IF" I remember right, the problem mixing dissimilar metals only happens if both the metals are in the solution (say salt water) at the same time - such as a bronze prop on a stainless steel shaft. In which case you'd attach a zinc to the shaft because zinc is less noble than bronze, and would erode away first from the galvanic action between the stainless and the zinc, saving the bronze at least till the zinc wore away.

So if you have an above waterline bronze thru hull attached to a dry stainless fitting it should be okay since both aren't in the solution at the same time.

NOW IF it is below the waterline, say an intake for the head, I would worry that both the bronze and stainless would be filled with salt water on the inside at the same time, and that would make for a galvanic path, eating away the bronze from the inside - not good !

If you have doubts you can attach a zinc to the stainless via a bonding wire, etc

If I'm remembering wrong, somebody please correct me ! It was this worry that kept me with plastic fittings, and I'd like to upgrade at some point as well.

CaptainScott · Post by **CaptainScott** » Fri Dec 05, 2008 7:07 am

You have it EE!

Also, I found an article here
http://www.sailnet.com/forums/gear-maintenance-articles/20111-understanding-electrolysis.html

Scroll down past the writers notes and there is a brief summary and some step you can take for protection.
Scott

Banshi · Post by **Banshi** » Fri Dec 05, 2008 9:35 am

Actually it does not matter they will still react because the dissimilar metals are swapping electrons at the contact point, water only hastens the process along. This is why electrical connections between aluminum and copper must have special protection to keep them from reacting to one another. For instance look at any stainless/aluminum connections of hardware on your mast.

STEVE ROYER · Post by **STEVE ROYER** » Fri Dec 05, 2008 2:16 pm

I'm going w/ thru hull , street 90 and ball valve all in bronze and kc in poly pro and s/s everywhere else, the hoses will isolate them. thanks for all the info