Heavy marine grease to protect valves on thru-hulls from corrosion?

[bcboomer]

Originally Posted by seagypsy50

I agree 100%. Proper Bronze is and always will be the Gold Standard! Have you ever seen what happens with a plastic through hull fitting when it is struck with a solid sharp object? Well I know a Marine Survey professional who has. It's why some are starting to question the wisdom of the 'fantastic plastic'. Not on my boat buddy!! Ever!

And I know a surveyor who has seen what happens when stray current dissolves bronze thu hulls and valves.
And don't forget the new boats being sold with brass valves.
Trudesign valves are plenty strong in real world use. They don't need greasing, they don't care if the neighbour boat or marina are leaking current into the water.
Their only shortfall is that they don't polish to a nice shine.

[sailorladd]

Anhydrous lanolin is the best for any threaded fitting under water... best kept secret You are welcome.

[DeValency]

Originally Posted by George_SD

I'm looking at a boat that has rusty valves/fittings/clamps on top of its thru-hulls.

What I'm wondering is why these valves and thru-hulls are not covered in heavy marine grease so that they are not exposed to air or moisture? I use heavy grease in non-marine applications to prevent metals from rusting over prolonged periods of time (like washing machine fittings that sit in contact with water for 10+ years). Typically this grease will not melt (under reasonable temps and if not exposed to direct sunlight and will not harden).

So why is this not used on boats? At least not the ones I've seen.


Anyone doing this to prevent corrosion from moisture and salt in the air?

Skin fittings and seacocks should be made from marine grade materials; metals - marine grade bronze, (never never brass!) and special composites. Covering any inappropriate fitting with grease is useless or worse - the salty water will attack from the inside quite fast and such fittings will fail - think of the consequences...

[john manning]

The product you are looking for is Denso Tape. It is a cloth tape that is impregnated with lanolin grease. Still commonly used on ships and fishing vessels to protect steel.

However for seacocks on small vessels I would recommend changing them to bronze or plastic. Ships still use steel valves because the valves are heavy walled and it takes many years for rust to erode the 20 - 30% of wall thickness that triggers valve replacement. Engine room valves on ships are normally just painted. Denso is used for those valves less often seen and only checked at survey.

[DeValency]

The short and long answer is No.

Originally Posted by George_SD

I must be terrible at communicating : I was asking if a new or otherwise in good condition seacock/valve is present - would it help to slather them in marine grease to prevent what is in the picture or significantly delay such issue?

[Dockhead]

Originally Posted by bcboomer

And I know a surveyor who has seen what happens when stray current dissolves bronze thu hulls and valves.. .

How does stray current "dissolve" a bronze through hull which is not wired to anything?


Answer: It doesn't.


To each his own -- plastic underwater fittings have their own pluses and minuses. Plus is of course their complete inertness. Minus is dimensional stability issues (original Forespar the Trudesign valves; maybe less nowadays), and impact resistance. Are they "strong enough?" For most purposes, sure. But still, make mine bronze, please.

[boatpoker]

Originally Posted by slug

Paint it

Metal sweats , then corrodes

Only one of many ways metal corrodes. Old paint can actually hasten corrosion if any moisture gets under it .... hidden from viiew. Use the correct material and it will out last all of us without paint.

[boatpoker]

Originally Posted by bcboomer

And I know a surveyor who has seen what happens when stray current dissolves bronze thu hulls and valves.
And don't forget the new boats being sold with brass valves.
Trudesign valves are plenty strong in real world use. They don't need greasing, they don't care if the neighbour boat or marina are leaking current into the water.
Their only shortfall is that they don't polish to a nice shine.

Well as a marine surveyor for 30 years and a retired Certified Marine Corrosion Analyst i've never seen bronze corrode due to stray current corrosion. Tell me more.

[Sailor_Grant]

Marelube is built to lubricate thruhulls

[boatpoker]

Originally Posted by George DuBose

That photo is a classic example of why the EU/Brussels says that seacocks must b replaced every five years.

This is incorrect, they (EU, RCD) say they must last five years. This bureaucracy is what permits Beneteau et al to use plated brass ball valves that corrode in 6-7 years in Salt Water.

http://www.pcmarinesurveys.com/Paul%...20Seacocks.pdf

[Davo1404]

Originally Posted by a64pilot

I’m thinking this may be brass, and not bronze.


That along with the hoses, look at all the money they saved

Is that swimming pool vacuum hose?

My thoughts. Definitely looks like swimming pool hose!!

[Uncle Bob]

Originally Posted by Davo1404

My thoughts. Definitely looks like swimming pool hose!!

They actually look like old style cuffed marine sanitation hoses to me.