Stainless Bolts on Bronze Seacock

[duncan_ellison]

Hoping that someone here will know more about galvanic properties than I do.

I am helping a friend to restore his 30+ year old Hurley 24/70 which has large bronze seacock (of the Blakes type for those who know this sort) which would be difficult to replace in the exact size and hole configuration, so we've sucessfully restored it but the bolts which secure it to the hull have seen better days and I would rather replace them as the seacock goes back in.

Trouble is I only have good quality stainless ones, not the phosphor bronze ones which came out.

Anyone know if 316 stainless in contact with bronze is a particualrly bad combination ?

Duncan

[s/v Jedi]

Hi Duncan,

I have that without trouble. I use TefGel which will make a difference though so that's what I would do. Also, you can put a nylon washer under the head of the bolt to further minimize contact. I have that on one seacock but must admit that the one without this just looks as good so it's not really a problem.

cheers,
Nick.

[roverhi]

We used stainless bolts on our bronze seacocks without a problem. I think if you look a little bit you'd find bronze fasteners, however.

[Watercolor]

Duncan,

As you probably know if the seacock is a Blake it's made in the UK. What you may not know is that it's actually made of a special form of brass, dezincafication resistant brass. I'm not sure how that fits in the nobility table.

However, I googled Blake seacocks and came up with the following site www.leesan.com/bundles/seacocks that may be of help.

INSTALLATION
Hull types: Blake seacocks are suitable for GRP,
Steel, Wood and Ferro-cement hull materials.
For GRP, wood or ferro-cement hull materials, the
spigot should be cut off to suit the outside of the
hull.
We recommend the fitting of a wooden pad, bond-
ed to the hull with underwater sealing compound.
To ensure water tight joints underwater sealing
compound should also be put under the seacock
flange.
For steel hull materials, the seacock spigot should
be cut off flush with the flange. The seacock
should be isolated with a gasket and studded with
stainless steel fittings.

Also you might contact Jamestown marine here in the States. They deal with alot of bronze nuts and bolts.


Hope this helps.

Fair winds,

Jed

[scubasteve]

I recommend using bronze if you can find them. Stainless is susceptible to crevice corrosion when used underwater. Plus when you have any dissimilar metals galvanic action will affect the least noble of the two.

I've had boats with stainless/bronze and did not have any issues, but if were installing or replacing a component, I would use the same material to be on the safe side.

[witzgall]

I had to replace several of the nuts and bolts on our Blakes Seacocks a few years ago. The yard was able to source them for us in bronze.

Chris

[duncan_ellison]

Thanks guys, sometimes I think there is (collectively) nothing this forum doesn't know.

It seems then that it shouldn't be a problem, but get bronze if you can find it and Tef Gel if you can't. Got it.

Duncan

[Watercolor]

Duncan,

As you may know, bronze is a very generic term for a wide range of metals. Blake uses, a form of brass not bronze. It's a specially treated brass that, I understand has had an excellent salt water track record. The bronze bolts that originally come with the Blake seacock appear to be phosphorus bronze. My tendency is to agree with scubasteve regarding bronze vs stainless, it has its own issues.

Because the Blake is made of brass, albeit, a corrosion resistant brass, there may be a reason for their choice of metals. I'd send them an email and ask.

[S&S]

jamestowndistributors.com

Go with bronze.

[scubasteve]

Originally Posted by Watercolor

Duncan,

As you may know, bronze is a very generic term for a wide range of metals. Blake uses, a form of brass not bronze. It's a specially treated brass that, I understand has had an excellent salt water track record. The bronze bolts that originally come with the Blake seacock appear to be phosphorus bronze. My tendency is to agree with scubasteve regarding bronze vs stainless, it has its own issues.

Because the Blake is made of brass, albeit, a corrosion resistant brass, there may be a reason for their choice of metals. I'd send them an email and ask.

Bronze is made of copper and tin
Brass is made of copper and zinc
Zinc is affected much more by electrolysis

I wonder what type of treatment they use?

[S&S]

Copper Alloy Number 464 -- Wrought Naval Brass,Non-Leaded

Naval Bronze, CDA 464

Specifications:Naval Brass or C46400 is a high strength, corrosion resistant alloy containing nominally 60% copper, .75% tin and 39.25% zinc. It is widely used in marine construction where a strong, corrosive resistant and hard material is required. It is available at a comparatively low cost.
Marine Propeller Shafts, Marine Hardware, Decorative Fittings, Shafting, Propeller Shafts, Turn buckles.
Industrial: Welding Rod, Condenser Plates, Structural Uses, Valve Stems, Balls, Heat Exchanger Tube, Aircraft Turn buckle Barrels, Bearings, Dies, Golf Ball Production, Pressure Vessels, Bearings, Bushings, Hub Cones

No "treatment" it's just the material picked.

[Laidback]

Here is the Link to Sparton - in Maine -- they can provide what you need
Bronze and Stainless Marine Hardware, Seacocks, Portholes, Thru Hulls - Spartan Marine Hardware and Accessories

[Maine Sail]

If I am not mistaken Blakes use 85 three 5 or 85-5-5-5 bronze which is also sometimes called machine brass, red brass, leaded brass etc. etc on and on. By definition it fits more into the bronze category than brass but the make up means more than the name. 85 three 5 has a zinc content of 5% or less and some added lead for easy machining.

Apollo/Conbraco, Groco, Spartan and most others use 85-5-5-5 bronze for bronze seacocks and thru-hull fittings I doubt Blakes is any different. 85 three 5 has been a very standard composition for seacocks and thru-hulls for quite a long time.

It consists of Cu (85), Pb (5), Sn (5), Zn (5)

While stainless might never give you any trouble, if properly installed, why not just order the bronze and not have to worry about it. Hamilton Marine in Maine is an excellent source for bronze as is Jamestown Distributors in RI.

[duncan_ellison]

OK, Thanks to everyone who replied here.

In fairness to everyone who replied I just want to clarify a couple of points.

This particular seacock is NOT a Blakes original (as far as I can tell), it's a "Blakes type" of unknown manufacture, but I expect that the composition is some form of DRB. The only clue is the manufacturer's marks "SLO402".

My own boat is in RI (not far from Jamestown Distributors), but right now, I'm in the UK helping out a friend and phosphor bronze bolts are a bit thin on the ground here.

Lastly, I would normally advise him to replace the whole thing with a new Blakes one, but he's on a very tight budget and also the number / size of holes is quite different to the Blakes equivalent (3 holes rather than 4), so this would involve epoxy work and potentially weaken the area.

Duncan

[FloridaWriter]

I would also use bronze fasteners. McMaster Carr and boltdepot.com are both good sources.

Good luck,