HOW TO Check & change anodes

Keeping your anodes in good order prevents serious damage on board, says Rubicon 3’s Bruce Jacobs

Galvanic corrosion is a phenomenon that affects the majority of boats. If you have two dissimilar metals, such as stainless steel and bronze, the water will act as an electrolyte and the less noble of the two metals, the bronze, becomes an anode and will begin to corrode. If this is a seacock, it could sink your boat. Electrically connect a less noble metal like zinc, and this becomes the anode, protecting the other metals from corrosion. In brackish water, the Baltic for example, you will need a more reactive metal, such as magnesium, to provide proper protection.

BONDING

Anodes only offer protection to metal they are electrically connected to. This means either in direct physical contact, or connected by a wire inside the boat. Use a multimeter in continuity mode to check bonded objects, such as the gearbox, have a proper electrical connection to the hull anode studs. There is mixed opinion as to whether every through-hull fitting needs bonding; the bonded object needs to be fairly close to the protecting anode, and there is a risk it could introduce corrosion from stray current where there was little risk before. The decision is one of personal preference. Your bonding system, if your through hulls are bonded, will also be connected to your negative battery bus bar. This gives a quick and easy route to ground for any stray current, rather than posing a danger to any humans on board who might touch those through hulls. There is also an increasing move towards high-strength plastic through hulls, which obviously negate the need for any type of bonding at all.

The foam pad stops the corroded anode damaging the hull The spring washer needs to be replaced along with the anode, as an old washer won’t be secure A worn anode is a good sign that it is working. More than 50% gone, however, and you need a bigger anode

GJW Direct offers some of the most comprehensive boat insurance policies on the market, at very competitive prices. With over 175 years in marine insurance, when you insure your yacht with us, you’re dealing with the boat insurance specialists, leaving you free to enjoy your time on the water.