Mixed metals for cockpit drain seacocks

[awyatybw]

The cockpit drain seacocks are made (I presume) of bronze (in general, the fittings on this Victoria 34 are of good quality). They are a ball-valve type. The actuating levers that they come with are rubbish - a thin plate of mild steel covered with a plastic grip. They do not have the inherent strength for the job, once the seacocks are in anything other than perfectly lubricated condition. And they have rusted badly. The retaining nuts have (all but one) gone missing - they are 1/2" imperial thread.

I have had some lovely replacements fabricated in A4 s/s. I have purchased new nylock nuts, zinc passivated. Now I am wondering, should I actually assemble this mixed-up collection?

Two of the seacocks are in the bottom of the main cockpit locker, used primarily for ropes of various sorts. It is not inherently wet or damp inside, in general, but of course soaking warps and other rigging are sometimes put in the locker. The third is in another, much less accessible locker which is dry.

An alternative to assembling the bronze/ss/zinc combination would be to tape the new handles onto the adjacent pipes from which they would easily be liberated if necessary. Is there a significant danger of galvanic corrosion if I put it all together?

 

[Topcat47]

SS does not work well with copper alloys. The resultant failure mode is crevice corrosion, which interferes with the chrome and nickle in the SS at a molecular level.

If the bronze units are salveable, now handles can be made from Bronze strip, with a bit of elbow grease and care with hand tools.

Otherwise, I'd reccommend replacing the hull fittings with something beter suited to the SS Seacocks.

 

[Topcat47]

Sorry, I seem to have misread you post.

I still would not reccommend SS for the handles, which would still be susceptible to crevice corrosion causing the handles to crack under load.

I, too have crap thin plate handles on my seacocks, but these will be replaced by thicker steel ones when they rust away.

 

[vyv_cox]

Absolutely no problem with your proposed arrangement, except for the nuts. The zinc will go fairly quickly, leaving the steel beneath to rust and leave deposits all over your locker contents. The combination you are proposing would be acceptable even if immersed (see May PBO and Nigel Warren's comments about anodes - he suggests none necessary) but in relatively dry conditions there is absolutely no problem. I have a bronze seacock with stainless ball valve exactly like the one in the article. It has been in place in my galley sink drains for almost certainly the life of the boat, 24 years.

There are loads of other places on a boat where bronze, or even brass, and stainless steel are in contact with no problems. Start with a look around your cooker, then your engine, then your clock and barometer......

 

[PCUK]

Well, Vyv, you just saved me some typing as I was going to quote you virtually word for word!
SS nyloc nuts are readily available from swindleries if there isn't a local engineering supplies. You will then have a near perfect system.
Incidentally I painted my steel handles with Hammerite and ten years on they are still good.

 

[No Regrets]

Just a thought, why not place a well oiled plastic bag over the seacock and lever, held in place with an elestic band, like a sort of stern gland arrangement.

It should keep damp out, preserve the contents, yet be easy to see and operate.


Just a thought!?

 

[wotayottie]

Whilst its not a combination that would keep me awake at night (I have a son to do that!) my preference would be to go for re-inforced nylon valve , skin fitting, the lot. Never need to worry again.