Ground Round

Lee Andrews of East Hampton, New York, asks: "I’ve had electrolysis issues on my Tartan 3800, so I’ve installed a galvanic isolator, I deploy a zinc grouper whenever I’m in a slip, and I use shore power only when I have to. When I hauled out last fall I could see my shaft zincs were far less corroded than in previous years, but paint continues to pop off my lead keel in
Author:
Updated:
Original:

Lee Andrews of East Hampton, New York, asks:

"I’ve had electrolysis issues on my Tartan 3800, so I’ve installed a galvanic isolator, I deploy a zinc grouper whenever I’m in a slip, and I use shore power only when I have to. When I hauled out last fall I could see my shaft zincs were far less corroded than in previous years, but paint continues to pop off my lead keel in 6in diameter swirls. I should mention that whenever I’ve taken the keel down to bare metal and then applied an epoxy barrier to the metal before repainting it with bottom paint, the problem has almost disappeared. What can I do to permanently solve this problem?"

Don Casey replies:

A bronze prop mounted on a stainless shaft creates an electrical connection, and when the two are submerged in seawater, the inherent difference in electrical potential will start current flowing from the more noble steel shaft to the less noble bronze prop.

Unfortunately, the flow of electrons destroys the bronze, which is why it has to be protected by zinc, which is a less noble metal. If a typical zinc shaft collar or prop cone corrodes too quickly, there must be an electrical connection to more underwater metal, perhaps bonding on your boat or a connection to the submerged metal of nearby boats through your AC grounding wire. A galvanic isolator should interrupt the DC flow between your boat and others that are plugged into the same circuit. (For a step-by-step installation project, see page 62.) However, isolators sometimes fail, which is why unplugging from shore power is the best solution. Typically anodes are sized to lose about 50 percent of their mass annually, so if your zincs are not disappearing significantly faster, your corrosion problem isn’t getting worse.

As for the paint flaking off your keel, you’ve already discovered the solution, which is to break the electrical connection between the copper and lead by encapsulating the lead in epoxy before applying bottom paint.

However, the circular swirls suggest that stray DC current may be leaking to ground through the metal keel. So make sure all your bilge pump circuits and any other wiring near the keel attachment is sound. In fact, I suggest that you test the entire DC system for possible leakage to ground.

Related

01-LEAD-Vento-Solare-action-(1mb)_Stephen-Cloutier

Ida Lewis Distance Race 2021

This year’s annual Ida Lewis Distance Race on Narragansett Bay will offer something for everyone. In addition to ORC and PHRF, there will be sections for doublehanded, youth and collegiate racing. Racers will also have a choice between the event’s traditional offshore distance ...read more

01-LEAD-Lag01-oon-620---Raiatea---French-Polynesia-(12)

Internships: Run Away to Sea

Not the office type? College isn’t an option, or your degree in philosophy isn’t panning out? If a job in the marine trades sounds like your dream career but you don’t know where to start, here are three places to both get some good training and a foot in the door. Dream Yacht ...read more

Screen Shot 2021-05-12 at 9.58.55 AM

Summer Sailstice Turns 21

Summer Sailstice’s will celebrate its 21st birthday this year. This annual worldwide celebration of sailing occurs on the weekend closest to the solstice, landing on June 19th this year. Over the past two decades, the event has grown to include nearly 5,000 boats and 19,000 ...read more

e60aa842-1c3c-41da-b0ba-dfd7678479e4

The New York Yacht Club Submits a Protocol Alteration with its America’s Cup Challenge

The New York Yacht Club (NYYC) has submitted a challenge for the 37th America’s Cup to the current Defender, the Royal New Zealand Yacht Squadron (RNZYS) in Auckland, New Zealand. The challenge was accompanied by a draft protocol for the regatta, which would see the Cup take ...read more

01-LEAD-CCA-Antarctica2-01

Cruising: Honoring Remarkable Ocean Voyages and Seamanship

The Cruising Club of America, an organization of about 1,300 offshore sailors, has been honoring remarkable ocean voyages and seamanship with an array of prestigious awards for nearly 100 years. The club’s highest honor, the Blue Water Medal, has recognized renowned and ...read more

2.4mR's racing at the 2018 Clagett Regatta-US Para Sailing Championships credit Clagett Regatta-Andes Visual

Host for 2021 U.S. Para Sailing Championships Announced

The 2021 U.S. Para Sailing Championships will be hosted by The Clagett Regatta at Sail Newport, in Newport, R.I. on August, 24-29, 2021, according to a joint announcement from the host and US Sailing. "We have had a very long working relationship with US Sailing and look forward ...read more

Reflections-photo-CMerwarth

Cruising: Reflections of an Old Salt

I am 90 years old, dwindling in mind and body and fear living too long. Twenty years have passed since I last weighed anchor. Still, when a Carolina blue sky is polka-dotted with billowing cumulus clouds and the wind blows fair, I sorely miss raising sail and setting forth. I ...read more

DSC_0145

Waterlines: Solo Sailing

In spite of the fact I came to the sport of sailing alone and untutored, in a boat I acquired on my own, I never really aspired to become a solo sailor. It just sort of happened. All these years later, I still never explicitly plan to sail anywhere alone. I’m always happy to ...read more