Deposits on Engine Zinc

[bcboomer]

After less than 60 hours the raw water engine zinc in my heat exchanger had such a build up of calcium/salt, or whatever, that I had to break it off when I pulled it out. It's on a Westerbeke W-46 and is moored in fresh water.

When I installed it I'm pretty sure I cleaned it off to a nice shiny surface.

My concern is that this same build up may be happening inside my cooling system.

Anyone else had this problem?

[Lepke]

It's the reaction of the zinc being attacked by the usual galvanic corrosion. Normal. You can sand or buff the corrosion off, but you'll get faster dissolving of the zinc.
Engine PencilZincs
A good place to get zincs, usually in the $2-5 range, much cheaper than the marine stores.

[sailorchic34]

For fresh water, zinc will oxidize and will have reduced effectiveness. You probably need to switch to a aluminum or magnesium anode. They provide superior protection in fresh water.

[bcboomer]

I've thought about the aluminium/zinc choice but haven't decided what would be best. Our boat is moored in the river but we sail in the Salish Sea so, ideally, it should have two separate sets of anodes.
More time in fresh but more engine hours in salt.

[GordMay]

Aluminum is a good "catch all" anode for a boat that frequents both fresh or brackish and salt waters, It has decent protection in either environment.
When making the switch from zinc to aluminum, ALL of your anodes must be aluminum.
When purchasing anodes, select those that meet military specification standards: A-24779, for aluminum.

[mike66]

Usually the heat exchanger is isolated from the bonding system by rubber hoses, paint, and neoprene strips on the holding brackets. I think the zinc is to protect the heat exchanger from itself and all the dissimilar metals it is made of. Trying an Al anode won't hurt anything. A switch to all Al can be done next season for the rest of the boat if desired.

Sent from my SAMSUNG-SGH-I337 using Cruisers Sailing Forum mobile app

[fryewe]

Originally Posted by bcboomer

I've thought about the aluminium/zinc choice but haven't decided what would be best. Our boat is moored in the river but we sail in the Salish Sea so, ideally, it should have two separate sets of anodes.
More time in fresh but more engine hours in salt.

If you're moored in fresh water such that the last minutes of engine operation are in fresh water (or brackish), that'll be the water that sits in the engine during the long inactive periods at dock when the anode is doing most of its sacrificial work.