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

[Dockhead]

Originally Posted by CarinaPDX

There is no need to paint or coat quality bronze parts. Bronze is literally forever: bronze items from the bronze age are often retrieved from shipwrecks at the bottom of the Med and they have survived for thousands of years. Bronze will form a thin layer of oxide, or patina, usually brown or green - and then it will stop (the valve body in the photo looks right). Polishing, sealing, and painting will not be nearly as durable as that patina so stop making work for yourself. The first problem is to get a high quality of bronze - there are many alloys and not all are equally strong or corrosion resistant. Unless you are into metallurgy just buy from quality manufacturers like Groco. Modern seacocks and ball valves use teflon seats and do not need lubricating although a little Superlube synthetic grease can be helpful. The marelon seacocks and valves are obviously corrosion-resistant but they must be installed correctly; in the early days some installed them with too much force on the fittings and had failures which showed up over time. Even the best designs can't protect against bad installations.

Looking at the photo (painful to do as it is) the street elbow appears to be an inappropriate alloy - there should only be a patina on the bronze, not a heavy layer of corrosion (again, the valve body looks about right). Most plumbing parts are a good brass but not really appropriate. I can't see clearly but it appears that the hose clamps may be rusting from the tightening mechanism. There are a lot of hose clamps that are stainless steel straps with something else for the adjusters: buy only "all stainless steel" - if it just says "stainless steel" then it often is not entirely that.There should be no rust on the hose clamps. It also appears that the handle may be starting to corrode; most bronze ball valves have plated steel handles. Either buy valves intended for marine use or pay extra for the optional stainless steel handles if available. Some marine vendors use cast bronze handles, which are very nice. I also agree that using a cuff on the spiral wound hose is not appropriate for below the water usage, and in fact the hose itself doesn't look good either. I am also suspicious that there is a thread mismatch between the thru-hull and the valve.

Thru-hulls have straight (NPS or IPS) threads. Most valves and plumbing parts, at least in the US, are tapered threads (NPT or IPT). NPS and NPT can mate but they will not seal properly nor will it be a strong connection - it is definitely not approved for marine use. So either the valve must have a female NPS thread for the thru-hull or an adapter is used. It is possible to find ball valves that have NPS on one end and NPT (for the hose barb) on the other but they are scarce. OTOH traditional seacocks with flanges are configured that way and are the best way of going. Equally good is using Groco's adapter flange, which attaches to the hull and the thru-hull threads into NPS, while an NPT male on top allows use of standard NPT valves.

I am still using bronze ball valves I first installed more than 40 years ago and they still look great. Unfortunately the handles were plated so I have had to track down the stainless replacements but other than that they are in great condition. No coatings were ever needed.

Greg

Great write up.


I had the same problems as you with the crap plated mild steel handles on the original Maestrini bronze ball valves on my boat. Actually other than the handles, all but a couple of the original ball valves were still in fine shape after 18 years of service.



To their credit, the company has learned from these mistakes, and the latest Maestrini ball valves have either 316 stainless handles, or beautiful nickel plated brass handles.






Anyone in the market for new ball valves should be sure to get the right alloy -- 85-5-5-5. And the right handles -- NOT indeed plated mild steel.

[onestepcsy37]

you can 'cheap out' on a lot of gear. but anything below the waterline can sink your boat in hurry. not a place to save money. we had wilcox crittenden bronze through hulls, seven of them. thirty five years old and as good as new with full maintenance every two years.

i also removed any underwater 'hole' that i didn't need. the depth sounder transducer was removed, hole sealed off, and replaced with an inside the hull transducer. knotmeter wheel was removed and sealed off as well. got my speed from my gps.

[billgewater]

If I had any valves or skin fittings looking like those I would be arranging a lift out and checking that the bilge pumping system is fully functional. It looks dangerous to me.

It does appear that the skin fitting itself may be OK but there is something seriously wrong with the rest of it. Looks like a minor leak in the presence of dissimilar metals. It won't get better by itself and it is highly unlikely that any applied product will stop and certainly will not repair the apparent damage.
The green stuff is an indication of salt water on a copper based alloy and the other dark stuff looks like rusting of an iron based metal - maybe the two hose clamps rusting. Could be wrong, but you really should be replacing everything.

The other valve and fitting also look suspect to me.

Have you had salt water in this part of the bilge at any time? It might be that what you are seeing is the consequence of that salt water not being thoroughly removed.

Just ensure that you use quality fittings that meet the highest standards and you will be a happy chappy. My own tub has many bronze skin fittings with valves and all are over 40 years old. I consulted the local fishing boat builders at the time who collectively had been managing these issues for generations. Checked carefully each lift out. No lubricants ever needed.
The minimal spacing for the valve handles also should be considered carefully. maybe a skin fitting with a longer threaded section, or with an extension, etc., may make it easier to manage the valve handle spacing.

[bcboomer]

Originally Posted by mitiempo

Yes they are very good.

They are Marelon, just not named as it is a Forespar trademark.

Marelon is Dupont Zytel which is a reinforced type of nylon.

Maybe, but what I see is very different from the Marelon I removed.
There have been numerous complaints about the Marelon valves sticking.
That's the problem I had and it is a real pain. Marelon need twice yearly lubrication and monthly operation.

One of my Trudesign valves was installed 6 years ago and not operated until this spring. Still smooth operation.
Can't be the same material.

[mitiempo]

Originally Posted by bcboomer

Maybe, but what I see is very different from the Marelon I removed.
There have been numerous complaints about the Marelon valves sticking.
That's the problem I had and it is a real pain. Marelon need twice yearly lubrication and monthly operation.

One of my Trudesign valves was installed 6 years ago and not operated until this spring. Still smooth operation.
Can't be the same material.

It is the same but the Trudesign are better engineered and made. I have sold both but I own all Trudesign.

[George DuBose]

Originally Posted by George_SD

So as an example, here is a picture of the valve/seacock on top of the thruhull. Obviously this is pretty bad and it needs to be replaced. However, if covered in marine grease or maybe painted with Rustoleum like someone suggested - would this help to prolong longevity.

That photo is a classic example of why the EU/Brussels says that seacocks must b replaced every five years. The valve (I wouldn't call it a seacock) is not only showing rust, but apparent dezincification.

That valve and all others in similar condition or age should be replaced. If you value your life and others, you will replace all your seacocks that are similar to that one in the photo.

Blakes, Sparta and Groco still make marine quality seacocks and Blakes even makes a proprietary grease, but most waterpump greases are fine.

Skylark has Wilcox-Crittenden bronze seacocks that were new in 1973. I removed them from Skylark as one of the first renovation projects. I put them in a auto parts washer overnight, disassembled them the following day, cleaned them of all old petrified grease and then polished them on a buffing wheel.

When the Admiral came to Skylark for an inspection, she saw the polished seacocks installed and asked if they were new. I said, "No, I just had them gold-plated to avoid corrosion." Really had the Admiral going with that one.

Moral of this email...buy cheap tools, you buy them twice...

[CarlF]

To answer the OP’s question, grease will not help. The primary problem is the elbow. This is some “mystery” alloy. Likely a cheap brass with cheaper metals like zinc thrown in. There’s a lot of this junk coming from Asia. It all looks fine when new.

The clamps actually looks OK except for the rust in the middle. This might just be a reaction coming from the elbow. Or it too might be a poor stainless steel from Asia with very little chromium.

The corrosion is largely galvanic where the dissimilar metals in the alloy are eating each other. Grease won’t help significantly.

The thru-hull and seacock might be OK once you get that elbow off. It’s hard to tell if the elbow is added or part of the seacock.

To the discussion of Marelon. Forespar makes two different products. The “OEM Series 93” valves is vastly superior to the other one and meetS ABYC standard. I’ve had them on my boat for 10 years and none have swollen, broken, or even needed lubrication. Here’s a neat video from MainSail showing it passing the ABYC test of a 500 lb side loading. Some bronze thru hulls flunk this test.

https://www.youtube.com/watch?v=SLvLKnzop-0

[bcboomer]

With all the issues and potential failures I don't understand why anyone would want bronze thru hulls and valves.

Trudesign have a complete line of valves and fittings, all well designed, that will never corrode. They are a permanent fix.

[a64pilot]

Originally Posted by George_SD

So as an example, here is a picture of the valve/seacock on top of the thruhull. Obviously this is pretty bad and it needs to be replaced. However, if covered in marine grease or maybe painted with Rustoleum like someone suggested - would this help to prolong longevity.

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?

[Dockhead]

Originally Posted by bcboomer

With all the issues and potential failures I don't understand why anyone would want bronze thru hulls and valves.

Trudesign have a complete line of valves and fittings, all well designed, that will never corrode. They are a permanent fix.

What issues? What potential failures? Bronze underwater fittings are still the gold standard. You need the right alloy (95-5-5-5) and the right design, and right installation, but that's true of anything. Bronze is highly corrosion resistant (as someone above said, we still find intact bronze artifacts which have been under the sea for thousands of years), strong, and much more fire resistant than plastic. Bronze is more dimensionally stable than plastic which makes the valves work better, with less sticking, than plastic valves.

That being said, there is nothing really wrong with the best Marelon plastic fittings, which have their own advantages and disadvantages. The total inertness of plastic is of course a very big advantage of Marelon; even the best bronze is somewhat subject to corrosion. Strength was always a big drawback of Marelon fittings, but the strength of those new OEM-grade Marelon fittings as tested by MaineSail is impressive (however, what is the i.d. of those, and does that restrict flow?).

But I'll make mine bronze, thank you.

[CarinaPDX]

Issues with bronze? What a joke. There is literally nothing on a boat that is nearly as durable or reliable as bronze. I have never heard of a single failure of a quality bronze part, properly installed. I have heard of Marelon parts failing, usually through over-tightening, The idea that there are two quality levels, one that is strong enough to meet ABYC standards and the other not, is just bonkers. There are good applications for Marelon, such as aluminum hulls where bronze would create a galvanic cell, but the idea that bronze is somehow less safe is laughable.

Greg

[seagypsy50]

Originally Posted by CarinaPDX

Issues with bronze? What a joke. There is literally nothing on a boat that is nearly as durable or reliable as bronze. I have never heard of a single failure of a quality bronze part, properly installed. I have heard of Marelon parts failing, usually through over-tightening, The idea that there are two quality levels, one that is strong enough to meet ABYC standards and the other not, is just bonkers. There are good applications for Marelon, such as aluminum hulls where bronze would create a galvanic cell, but the idea that bronze is somehow less safe is laughable.

Greg

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!

[joelhemington]

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?

Good quality Bronze sea cocks aren't that expensive (boat bux wise) and are fairly easy to replace if the boat is on the hard. If the thru-hulls (aka skin fittings) themselves were made of steel this could be a real chore but one that needs to be done if you don't want your boat sinking. I think I'd look this boat over carefully as it appears the builder cut some corners.

[Nicholson58]

Originally Posted by wingless

The factory sprayed all the marine metal attached to my hull w/ Cosmoline during the assembly process.

All of my bronze seacocks were removed by me, polished to a shiny brass appearance, coated w/ metal prep, epoxy and Rustoleum, well over a decade ago.

They still have a glossy / shiny plastic appearance.

Did you remove the tiny pipe plugs and install grease zerks? I installed SS grease fittings. This makes it easy to lube the ball between the inner and outer seals.

I think the OP was talking about the visible hardware after the sea port connection. These hose clamps, even SS, will rust after a few years. Band clamps must be double. Hoses dry out and crack after a few years. Goo you might apply to the hoses could damage the rubber. If there is corroding steel after the sea cock I would look for replacement materials.

[wingless]

Originally Posted by wingless

The factory sprayed all the marine metal attached to my hull w/ Cosmoline during the assembly process.

All of my bronze seacocks were removed by me, polished to a shiny brass appearance, coated w/ metal prep, epoxy and Rustoleum, well over a decade ago.

They still have a glossy / shiny plastic appearance.

Originally Posted by wingless

Here are some images of my seacocks, up through metal prep, not showing epoxy or Rustoleum.


Original Natural Patina


Polished Seacocks


Pettit 6455/044 Metal Primer

Originally Posted by Nicholson58

Did you remove the tiny pipe plugs and install grease zerks? I installed SS grease fittings. This makes it easy to lube the ball between the inner and outer seals.

No, when I contacted Apollo Conbraco to inquire about that and to inquire about lubrication, they informed me to not replace the drain plug with a grease Zerk fitting and that lubrication was not required.

They related that injection of grease at that point could damage the tight fitting PTFE seals, destroying the seacock.

My servicing of these seacocks lead me to discover that the optimum service is to remove the handle, remove the stem nut, remove the stem seals, clean and grease all those stem parts, then assemble the stem nut until snug, not tight.

That service changed my seacocks from difficult to operate, to now easy to operate, with normal movement effort.