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

[George_SD]

Originally Posted by StoneCrab

I grease everything that moves, including seacocks and the head pump. I can't see a downside.

From the op post though I read it as a question about slathering the outside of the valves. To be clear, I grease the moving parts and use neversieze on fasteners, not outside surfaces.

Yes, perhaps I should have been more clear - i did talk about really slathering valves and seacocks on the inside with grease to prevent air/moisture/salt form getting to them.

[wingless]

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 setup does not look appropriate.

The hose clamps have excessive corrosion and have exceeded the safe service life.

Those white hoses / hose cuff do not appear to be appropriate for below waterline usage. All of my below waterline hoses are smooth / wire reinforced and rated for below waterline usage.

[moseriw]

I woul not even think of some prolongation. Get out of the water and replace this scrap NOW! This is dangereous. Look at the others too.

If you have an oldtimer like mine use grocco else ou are best off with marelon

[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?

[sailingchiro]

I grease or vaseline inside the thruhull upon haulout/bottom job and work valve many times. I also spray protectant on thru hull in bilge about every 3 months. I do this with my checking all the hose clamps. Found 3 hose clamps rusted badly or broken last weekend. Even with coating them.

[wingless]

Originally Posted by wingless

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.

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

[moseriw]

so you think this is bronze? The green corrosion is usually only with brass, not with bronze!

So well IF it is bronze just clean it and connect it to the sacrifying anodes too.

[moseriw]

even the shiny parts look more like brass than bronze. Bronze is a lot more reddish

[wingless]

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?

The rate of bronze disease on new marine parts will be decreased by protection from salt water exposure, including from usage of a grease coating or a Cosmoline coating.

Correction of the plumbing to eliminate salt water leak exposure will also decrease the bronze disease.

[Monte Cresto]

I've been using Dow Corning High Vacuum grease now for 29 years
on everything. I even use it on the packing for the shaft gland with
not a drop of water and stays cool for extended periods of use. Although
expensive, most of my commercial fishermen friends have also started
using it.

[wingless]

Originally Posted by moseriw

so you think this is bronze? The green corrosion is usually only with brass, not with bronze!

So well IF it is bronze just clean it and connect it to the sacrifying anodes too.

Originally Posted by moseriw

even the shiny parts look more like brass than bronze. Bronze is a lot more reddish

Thanks for that information, very helpful.

Yes, these are UL rated Apollo Conbraco bronze seacock ball valves, in one example being this 78-119-01 1-¼" flanged valve, as-documented on the label attached to the handle.

Bronze is a terrific metal and when properly polished will resemble brass, as-shown in my image.

In all cases, all of the underwater metal is bonded together and all is connected to my hull zinc anode.

[mitiempo]

Originally Posted by bcboomer

Trudesign composite thru hulls and valves are superior to Marelon.
They don't seize if not used and meet ABYC standards.
I've had them for 6 years

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.

[Dockhead]

Originally Posted by slug

Huh ?

He said it's RUSTING. Anything which rusts, is unsuitable for underwater fittings. If you protect the outside, it will just rust out from the inside and sink your boat one day.

[Dockhead]

Originally Posted by wingless

That setup does not look appropriate.

The hose clamps have excessive corrosion and have exceeded the safe service life.

Those white hoses / hose cuff do not appear to be appropriate for below waterline usage. All of my below waterline hoses are smooth / wire reinforced and rated for below waterline usage.

Originally Posted by moseriw

I woul not even think of some prolongation. Get out of the water and replace this scrap NOW! This is dangereous. Look at the others too.

If you have an oldtimer like mine use grocco else ou are best off with marelon

Agreed. What is depicted there is hideous. That vessel should come straight out of the water. Budget for complete replacement of all underwater fittings and hoses.


Use 85-5-5-5 bronze fittings like Groco or Maestrini, and be careful to avoid NPT-NPF thread mismatches. Make sure and use proper quality underwater rated hose, and quality 316 hose clamps.



It will cost money and a lot of your time, or a lot of money, but you will be satisfied afterwards. I just this spring replaced the second half of my ball valves, spent a couple grand despite doing all the work myself, but it feels good to have all new quality fittings.



Don't let sea water slosh around in your bilge -- ever. The only excuse for a wet bilge is rainwater down a keel stepped mast, and that is fairly benign. If you can keep seawater out of the bilge, then the fittings won't corrode too much.

[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