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

Shelly-forward-last-day

Charter Advice for First-Timers

Never chartered? No worries. A vacation under sail can be the most memorable time of your life. That said, it also pays to be prepared by doing some reading, building your skills and listening to what the experts say. First and foremost, not all charter grounds are created ...read more

HugoBoss

Video: Vendeé Update

Last week Alex Thomson (Hugo Boss) led the fleet across the equator. As one of the class' top sailors who's been on the Vendeé Podium twice, it seemed possible that Thomson was going to grab an early lead and hold on to it all the way around the world. But early on Saturday, he ...read more

AdobeStock_229409051

Chartering Again for the First Time

It’s been a rocky road of late for the charter industry, especially here in the Western Hemisphere. First came hurricanes Irma and Maria in the Caribbean followed by Dorian in the Bahamas. There has also, of course, been the coronavirus, which burst into global prominence ...read more

01 LEAD cedaryachtclub_onedesign18_hike

An Interview with Ayme Sinclair

In recent months, US Sailing, like many organizations, has been taking a closer look at diversity to ensure it’s doing the best job it can of introducing people from all backgrounds and ethnicities to the sport. As part of this effort, this past summer it organized an online ...read more

125768940_10222759720523627_5373654001582879638_n

US Sailing Presents Adaptive Sailing Panel

On Tuesday, November 24, US Sailing’s Leadership Forum will present the latest panel discussion in their Diversity, Equity and Inclusion series. This event will focus on adaptive sailing and provide practical recommendations for organizations looking to expand their adaptive ...read more

02-IMG_5971

A Carbon Neutral Circumnav with Jimmy Cornell

Historic anniversaries have always held a special fascination for me, especially if they mark a significant nautical achievement. In 1992, on the 500th anniversary of Columbus’ would-be voyage to India, I organized a transatlantic rally that followed the historic route of the ...read more

DJI_0068

SAIL Podcast: Jimmy Cornell’s Carbon-free Circumnav

In this episode of Point of SAIL, Principal Editor Adam Cort talks with bestselling author and pioneering bluewater sailor Jimmy Cornell, who set out November 19 on yet another circumnavigation aboard a newly designed, carbon-neutral Outremer 4Zero catamaran. The voyage, which ...read more

emirates-600x

Emirates Team New Zealand Splashes the last of the AC75s

Emirates Team New Zealand unveiled its second-generation AC75 yesterday, joining the other three America's Cup teams with boats in the water. In just over 100 days, this boat will attempt to defend the Cup for the Kiwis, but there's plenty of racing between now and then, with ...read more