Zinc Anode for Aluminum hull RIB?

[ErBrown]

Howdy Folks,

We just picked up a new AB Lammina 10AL dinghy. We plan to keep it in the davits or on deck when not in use but I noticed in the manual there is a very vague mention of adding a zinc to the hull to protect it. Of course, there is no real detail on where it should be mounted or how and I'm currently away from the boat.

So after dropping a significant chunk of change on the dink, we want to do everything we can to maximize it's useful life.

My question is, has anyone out there added a hull or transom zinc to an aluminum hulled RIB? If so, how did you go about doing that?

[Jim Cate]

OUr aluminium hulled rib is ~11 years old, has been in constant use, left in water except when on passage. No zinc, and no corrosion. I think it is a non-problem, as do the thousands of "tinny" skiffs used around Australia... never saw an anode on one of them!

Jim

[transmitterdan]

Corrosion happens when 2 dissimilar metals are in contact with a fluid that is an "electrolyte" which salt water is one. The aluminum part of the boat probably has no non-aluminum parts in contact with the aluminum. I would recommend that you not add any other types of metal either. Aluminum is very low in the galvanic scale so many any other metals will react with Aluminum. If in doubt ask the manufacturer but I would not attach any metal to the hull. Stainless steel is especially hard on aluminum immersed in salt water.

[ErBrown]

So y'all are saying the same thing I was originally thinking. But the owners manual says "It is advisable to add extra zinc anodes with clean and tight connections" to protect aluminum boats if they might be subject to corrosion.

That and a couple stories I've read recently about folks with aluminum RIBs having problems have me concerned. On one hand my suspicion is that this would only really be a problem if you left the dinghy in the water for extended periods of time in a marina or busy mooring field. I can't imagine a time when we'd do this, particularly since we have a nice set of davits on the arch.

Then again, a zinc sounds like cheap insurance for a pricey investment...

[UNCIVILIZED]

You could glue a few pieces of cut up beer cans to the dink's transom, with their bottom edges set low enough so that they're in the water when the dink is. Just be sure to leave some metal to metal contact when glueing them to the transom, assuming it's aluminum too. Otherwise cut the pieces so that they're also in contact with the dink's aluminum bits in addition to the transom.

Or, just leave a few old beer cans in the dink's bottom. Probably not as effective, but easier And in a sailboat bilge beer cans tend to start springing leaks in about 3 days when wet, so the above ideas may well work. Note: This was tested on a racer that we re-purposed the keel coolers to aid in keeping our reserve beer stash in the bilges cool. So yep, 3 days.

[Mango51]

My be a drain plug screw made out of zinc. What about the outboard it has zincs.

[uncle stinkybob]

Originally Posted by ErBrown

So y'all are saying the same thing I was originally thinking. But the owners manual says "It is advisable to add extra zinc anodes with clean and tight connections" to protect aluminum boats if they might be subject to corrosion.

That and a couple stories I've read recently about folks with aluminum RIBs having problems have me concerned. On one hand my suspicion is that this would only really be a problem if you left the dinghy in the water for extended periods of time in a marina or busy mooring field. I can't imagine a time when we'd do this, particularly since we have a nice set of davits on the arch.

Then again, a zinc sounds like cheap insurance for a pricey investment...

Makes me wonder how hot those marinas are? The harbormaster here checks the docks for electrical bleed to water, even finding a bare live 110v wire hanging in the water. Even metal laying on the bottom in your marina can contribute to galvanic corrosion. My aluminum dink live's in the water, it has some galvanized hardware, some ss hardware and it's not a problem here., that could change in a different area I guess.

[Paul Mazza]

A lifetime ago I sailed around the Pacific Coast and Hawaii in my Columbia 33. She had an aluminum centerboard. It was connected by a SS cable to a bronze winch in the cockpit. It suffered badly from corrosion. I installed some outboard motor zincs (mangnesuim zinc), they greatly reduced the corrosion.

[Scaramanga F25]

Never had any corrosion on my alu/rigid inflatable over a period
of 5 years in the tropics.