Electrolysis experts - galv steel vs bronze

[Skipper]

I have a deep keel sump, with now a diaphragm bilge pump remotely mounted. Long story of pump reconfiguring to original mfg specs, but one part of it I could not figure out any other solution except to put the float switch on a galvanized steel tang, as the bottom of the sump is inaccessible for planting screws.

So I mounted the switch to an L-shaped tang, and lowered it into the bilge, then secured it to the cabin sole wood frame. The setup works perfectly. Would like to have found a plastic or other inert material, but couldn't.

My concern is that the pickup is made of bronze, and is an inch away from the tang. Both are constantly wading in about a half inch of brackish water at the bottom of the sump. Is this a setup for corrosion? Would attaching a zinc to the tang help?

I don't care about the tang replacement cost. It's a $5 piece of galvanized steel from the hardware store. But it's a pain to install, and I would like it not to covertly break, rendering the switch inop.

Thank you

 

[mudtertel]

I also had leaks,in my sailboat.After replaceing ,removing the toerail ,cleaned it up and put down new byuter tape( not sure if I spelled it right).It's dry as a bone.Only water I get is from my Icebox.Just a thought. I sail on the Hudson River ,where I'm at (in Ossining)is brackist water.

 

[Paul F]

Would suggest a plastic cutting board cut to size instead of the steel. Or get stainless steel. You will not be happy with galvanized steel as it will rust before the year is out.

 

[Skipper]

I also had leaks,in my sailboat.After replaceing ,removing the toerail ,cleaned it up and put down new byuter tape( not sure if I spelled it right).It's dry as a bone.Only water I get is from my Icebox.Just a thought. I sail on the Hudson River ,where I'm at (in Ossining)is brackist water.

The boat doesn't leak. The stuffing box does. In any case, no way to get the last 1\2 inch of water out, except maybe a tiny mop. And then it would be back next time I motor anyway. better to get the setup right.

BTW the bilge sump is in the keel space, aft of the ballast. The bottom of the sump is only about 4 inches by 8 inches.

 

[Skipper]

Would suggest a plastic cutting board cut to size instead of the steel. Or get stainless steel. You will not be happy with galvanized steel as it will rust before the year is out.

Thanks, Paul. What about an anode attached to the tang?

Also, the cutting board (or starboard) idea is good, but the bottom of the sump is 3 feet under the sole, and partially covered by the shower sump glassed in at the middle. There has to be an L-shaped bracket to lower and then secure the assembly. I couldn't find anything.....except the steel tang.

 

[Paul F]

An anode attached to the tang will help of course and may solve the problem. Seems a bit complicated though.

 

[mauruuru]

why not just make an L shaped bracket out of the plastic. You can buy it at West Marine cut it to shape epoxy and screw the "L" to the arm and its going to be just as strong as the galvanized steel for your use!

 

[ebartlett]

Will the bronze and the L-tang be touching? If there is no contact there shouldn't be a galvanic reaction. Where there might be a reaction is between the switch mounting hardware and the tang. I expect the screws mounting the switch to the tang are stainless, these two different metals can cause an electrolytic reaction. Once the galvanized layer (zinc) is gone the steel underneath will rust. It seems 316 Stainless would be the best material.

 

[Skipper]

Will the bronze and the L-tang be touching?

Nope.

Where there might be a reaction is between the switch mounting hardware and the tang.

Ooh. I didn't think of that.

It seems 316 Stainless would be the best material.

It would have to be custom made. $$

Another said to make the whole thing out of plastic, using (starboard) from WM. That's a good idea and I looked at that, but the Starboard I've found is uneven (warped), too thick to let the switch rest on the bottom, and unbelievably expensive. It would also be a sawing and fastening project, which seems excessive for just an L mount.

 

[alexco38]

Metal super market sells SS flat, it isn't hard to work with. Just use low speed on your drill and lots of cutting oil. SS is not much harder than galvanized steel. Just generate more heat when drilling and cutting.

You can also use the field effect bilget switch to help with fabrication:
http://levelguardproducts.com/marine-rv/sumbersible-bilge-pump-control.php

I have this at home for the 12v backup sump pump.

FWIF, a small wet-dry vacuum cleaner will get the last bit of water out. !!

 

[victorhoisington]

OK, I'm sure this is blasphemy for those who must have an absolutely dry boat but, why go to all the trouble of getting down to the absolute bottom of the sump? If it's hard to reach you will not be able to do anything with it when it does fail and will spend countless hours trying to fish out pieces. from the depths of the sump. Put it somewhere you can easily access and check. The last thing you want is for the switch to fail when you aren't around or even worse while sleeping.

A little water in the very bottom won't hurt (unless you are racing) and having easy access to the switch will ensure you can check it and fix it whenever needed. Put the automatic switch in an easy to access location where it will keep the main part of the bilge dry, if you must have that last little bit of water out of the deep sump, drop a small hose into the depths of the sump connected to you main pump and manually switch the pump on to pump it out each time you leave the boat. It should take less than 30 seconds to drain and you haven't had to do some un natural gyrations or unnecessary worrying about if something has corroded and failed.

Just a thought but, I've found when things go out of site or are hard to get to I don't always spend the time to check on their status. You don't want to get home from a weekend on the water and then begin to worry is my automatic bilge pump working.

Victor

 

[alexco38]

A little water in the very bottom will hurt because of mold and mildew. I vacuum them out every once a while.

 

[gettinthere]

I have a similar deep pocket where I need to have a float switch and pick up hose. I used flat aluminum bar stock. Easy to bend into L bracket shape.
If you dont want any metal sitting in bilge water perhaps fabricate a short plastic foot that can be fastened to the metal bracket well above the bilge waterline

 

[centerline]

A little water in the very bottom will hurt because of mold and mildew. I vacuum them out every once a while.

if you are having a problem with mold and mildew in the bilge water, then its only because you dont have enough oil in there....


anyone lucking enough to have a perfectly dry bilge is rare, as hulls sweat, ice boxes drain, and a fitting somewhere will be leaking soon.... more commonly from the cockpit area, as we tend to pay better attention to the fittings that leak into our living space
...and a boat with a steady influx of water wont grow mold or mildew in the bilge, but if there is dust/dirt, trash, a piece of wood or other objects that can soak up and hold water, then you could have mold and mildew begin to grow....

since the beginning of time, boats have had water in their bilges. they are designed and built for it....

a deep sump bilge is different than a shallow sump, or a boat without a sump at all.

a float switch will only cycle the pump while the switch is floating.. as soon as it pumps enough to let the switch come to rest, it shuts the pump off. so......
if you only have one bilge pump in a deep sump bilge, you should have the float switch up a bit higher. when it cycles on, you have the option to let it take care of itself, OR, you can flip the on switch and clear it all out so the pump wont be cycling as often. if it does you need to check for a more aggressive leak somewhere.

a piece of 1/8th" X 3/4" stainless flat bar is completely acceptable to use as a float switch mount/hanger, without anodes attached because there is absolutely no need for them on the float switch mounting.
and fit it high enough so you can reach it to periodically test the float switch manually (which will put it above the pump a reasonable distance).

if you have two bilge pumps in a deep sump bilge, having a bigger pump set up as described will be a good back up... a small pump can be set up in any manner you want to set it up for keeping the bilge relatively clear of water. but having the float switch a bit higher is usually desirable.
there are delay timers and such available that can be installed between the switch and the pump, but that getting more costly and complicated, when flipping a switch will eliminate the need for the extra time, trouble and maintenance required...

my bilge is 40" deep, 8" wide and almost 60" fore and aft. it will hold a lot of water.
my float switch is 24" above the pump... the only time it has activated was when I washed the laz and engine area....
whenever I have kept a boat moored, I have always been in the habit of flipping the bilge pump switch whenever i got back to the boat. it pumps out and I turn it off. so it is no problem at all, yet it has all the security needed to let me know when i have excess water in the bilge.
its not a sin to have a bit of water in the bilge, but oil is a whole different story...

 

[Bill Roosa]

It is a little known fact that galvanized steel is coated with zinc, so you already have a zinc down there. Just keep an eye on the galvanization and replace when needed. It will protect all the other stuff down there too as long as it is bonded electrically to the galvanized bracket
solved

 

[Skipper]

Metal super market sells SS flat

A good resource, for this application and many others. Thank you.