Boat zincs

[puddle jumper]

Wondering if anyone has had much to do with boat zincs. I have talked with many people in my area and all agree that an aluminum boat in salt water should have them. I was also told that having to little or to much zinc on your boat does not help. Is there a formula or something out there to find the right amount of zinc to put on a boat?

Thank for all imput

 

[rebars1]

Re: Boat zincs

Edit

 

[puddle jumper]

Re: Boat zincs

I have a small zinc in my Chris Craft. It holds just enough water to wash my face in the morning. It drains to a holding tank.

 

[seabob4]

Re: Boat zincs

Not a very helpful post there...

Your engine zinc should handle the corrosive effects of saltwater just fine. The boats DC ground, through the batteries, is tied into that zinc. If you were to add a LOT more equipment, and outfit your boat with shorepower, I would consider an additional hull mounted "sacrificial anode"...

 

[wingmastr23]

Re: Boat zincs

I have a small zinc in my Chris Craft. It holds just enough water to wash my face in the morning. It drains to a holding tank.

LOL! That was funny.....not very helpful....but, humorous!

 

[JoLin]

Re: Boat zincs

Yes, you need zincs, and no, there is no 'upper limit' to how many you can have. You were told wrong.

Some of the metal boat owners will probably chime in with more specific advice on placement,

 

[Philster]

Re: Boat zincs

Zincs: Yes, for salt and brackish water.

Size of zincs is limited to practicality. They can be too big in the sense that they can interfere with operation of the motor/drive. They cannot be so big that they'd prevent corrosion.

What we are discussing are anodes, which come in aluminum and zinc.

First you decide if you need anodes on your boat/drive/motor to prevent corrosion. Then you decide if they should be zince, aluminum, etc.

 

[JoLin]

Re: Boat zincs

OP mentioned salt water. He'll want zincs instead of aluminum.

 

[Philster]

Re: Boat zincs

Missed the salt water part. You should have zinc anodes attached to the hull. You need to clean the area where the zinc will be attached. Use a palm sander to remove any paint other than the surface finish: the key to cathodic protection is solid, uninterrupted contact between the zinc and the boat. Rinse your hull after you sand, to remove any residue that may interfere with the required contact.

Hold the zinc up to the side of the boat before you drill the holes and use a pencil to trace through the mounting holes in the zinc, marking the hole locations directly onto the hull of the boat

Drill 1/2 inch holes in your hull, using the tracings of the zinc's mounting holes as a guide, then hold the zinc in place, insert the bolts through the zinc and the hull, and screw the nuts onto the bolts. Tighten the nuts into place until the zinc is firmly against the hull.

Solder a wire to the nut onto the bolt, using silver-core solder. The American Boat and Yacht Council, a boating industry organization, recommends adding a "bonding wire," soldered to the nut and grounded on the engine block of the boat.

If you paint the bottom with anti-fouling paint, you need one specifically designed for alum boats. If you use one with copper or other metals, your hull is in for a serious hurting.

Keep pennies and other loose metals off the boat floor! Aluminum sacrifices itself to just about every metal it comes in contact with, except for zinc and one or two others.

If the zincs oxidize when out of water, the oxidation protects the zinc (bad) and the zinc won't be able to sacrifice itself, leaving the alum boat to corrode.

If you have zincs on the motor, you might be protected throughout the hull, but consensus is that zincs on the hull are the absolute surest way to go about preventing corrosion.

 

[Ned L]

Re: Boat zincs

Ah, things are getting a bit confused here. In a marine environment there are pretty much two separate causes for corrosion on underwater metal parts.

1) Galvanic corrosion: This is a due to an unavoidable law of physics. When you connect two different types of metal together and put them in salt water (an electrolyte), one of the metals (less noble) WILL corrode away, and the other metal (more noble) WILL be protected from corroding. (You have effectively made a battery here & this is what happens in a battery.) The galvanic series table (look it up on line) will tell you what metals will be protected (higher up the table) and what metals will corrode away (lower on the table). When we use ?zincs? (really sacrificial anodes) we are bolting a less noble metal (the zinc) to a more noble metal (prop shaft), so that the zinc will corrode away, and keep the prop shaft from corroding. Now ?sacrificial anodes? are not always made of zinc, the ones that are bolted on outboards & I.O. lower units (I believe) are typically more of a magnesium alloy (lower than zinc in the galvanic series). This is because aluminum and zinc are very close together on the galvanic series, so zinc would not work very well in protecting the aluminum. Sacrificial anodes or ?zincs? should be used on underwater metal parts of boats which are kept in the water all season. (In theory, a metal hull boat does not need them on the hull IF the hull is painted and there are no scratches through the paint ? yea right, like that?s not going to happen.) On steel hulled commercial boats, the zincs are welded right to the hull.
2) Stray current corrosion: This when there is a problem with the onboard wiring system in a boat, or near by a boat (wiring on docks, the pier, or another boat nearby). In this situation there is typically low level current being driven into the water by a near short in the wiring somewhere, or some voltage potential going to ground (the water). This problem will cause corrosion in all the metals in the water, and will not be reduced, helped, or fixed with the use of ?zincs? or sacrificial anodes. This is a wiring problem that needs to be corrected, and if not corrected can cause real damage.

As for ?Bonding? of metal parts on a boat, there has always been & still seems to be disagreement, I?ll leave that alone. I don?t do it.

 

[Philster]

Re: Boat zincs

Simpler:

Alum boat in salt water = zinc anodes.

Alum is a sacrificial metal, since it's less noble than just about everything. It's a big anode in the water versus just about everything else.

To the thread starter: Aluminum boat manufacturers recommend or even require (for warranty) zinc protection for their aluminum-hulled boats in salt water.

 

[Ned L]

Re: Boat zincs

I believe that sacrificial anodes designed for use on aluminum tend to be more of a magnesium alloy rather than zinc. Zinc and aluminum are to close together on the galvanic scale. (People may call them "zincs" for aluminum boats, but they are really more of a magnesium alloy.)

 

[seabob4]

Re: Boat zincs

Magnesium and aluminum sacrificial anodes are recommended for use in fresh water, zinc in salt...

 

[Philster]

Re: Boat zincs

For aluminum boats in salt, you can opt for zinc anodes or zinc-aluminum alloy anodes. Zinc-aluminum anodes don't oxidize over as easily, but...

...zinc anodes are more popular and easy to find (might be cheaper, too). As long as you make sure they don't completely oxidize over, go for it.

I am not using the words interchangeably. This discussion is about the proper anodes for an alum hull in salt water. The proper anodes are zinc OR and zinc-alum alloy.

Magnesium might be the choice for fresh water. That is out of scope for this conversation.

Thanks.

~Phil

 

[Ned L]

Re: Boat zincs

Oh, sorry about that, Thanks for the correction, I guess my knowledge was 'a bit out of date'. I'll just leave it at that. :redface:

 

[puddle jumper]

Re: Boat zincs

Thanks for all your input. Did some more research and you guys are right on that you cant have to many zincs. The rule of thumb that i found is to have enough zinc on you boat that will wear half out in one year and replace them once a year.

So I will have to do some trial and error with some time to see on how much to put on.