Anodes: Elementary

The prop minus the magnesium anode suitable for fresh water. The prop's been cleaned since and the anodes arrive this coming week from Nautilus Propeller.

Between boat stuff, the annual tax-prep collation, and doing some final fixes on the rental-income house in Trenton (which was rented to a nice couple as of April 1!), it's been a very busy time here in Alchemy Land. In fact, until the last weekend in April, we are on land in "winter mode" and are doing the things necessary to enter the boat's natural element of water without bringing too much of it inside, so to speak.

Great for ventilation, less so for buoyancy.

There was a superflous speed wheel mounted in the hull to a long-gone sensor original to the boat on the port side of the engine bay right where I pictured putting a water tank. So I had welder-fabricator extraordinaire Andrew Barlow plate it over...

This involved deployment of the fire blanket. I've been down this sparky road before. Oh, and that gruesome parquet flooring in the pilothouse will be gone in the near future, along with the yard dirt it's collected.

The burning ring of fire.

Andrew put in extra material to ensure not only watertightness, but strength.

I have referred to this book in the past. It's a great compendium for any boat owner, but has particular relevance for the metal boat owner in understanding the role of stray current in the water due to marina wiring, faults in the power setup aboard or other related issues that can eat (in our case) steel.

Yes, that's the aft bilge, or "smugglers' cove". You can see where the bead is running by the cooking off of the plate. And no, I didn't breathe in the smoke, which is toxic.

To this end, I decided that the impending cruise down the St. Lawrence needed a rethink of the somewhat casual approach to anode deployment on Alchemy...casual not because we were ignorant of the issue, but because we had some basic anodic protection in the form of magnesium anodes on the bronze prop hub and on the aluminum rudder and little evidence of damage elsewhere.

But we can't count on being in well-serviced waters once away from home waters. So I decided to acquire anode plates. Big anode plates.

DO NOT PAINT. To do so indicate a misunderstanding of the function!

Aside from "Martyr" being an apt name for a "sacrificial anode", I have come to accept that aluminum anodes of this particular grade are the best choice for our steel boat, and even for our aluminum rudder (of a differing composition/grade of aluminum). After a fair bit of research, I think aluminum anodes are the way to go. Should I change my mind, we can always switch, thanks to the way these are attached to the hull, to zinc anodes, which are also appropriate for salt water...which, after all, we won't be in until we pass Quebec City. Magnesium is right out in salt water, by the way...it apparently fizzes away in a matter of weeks should stray currents be present.

The daily grind of the boat fixer.

There are, typically, two ways to put the anode in contact with the hull material it is supposed to protect. One is by removing all the coatings on the hull to reveal the bare metal, and then directly welding the anode by tabs on its ends to the hull. This is common on commercial ships.

A "dry-fit" of one of the anodes prior to taping off the plate when we reapply this season's anti-fouling paint (Pettit Horizons)

The second method is to make a mounting plate with welded in studs of appropriate length on which the anodes can be bolted. This involves grinding off the coatings to the area of the mounting plate and welding the plate (which is stainless steel plate with 1/2 inch stainless steel studs) directly to the hull. This gives the desired direct connection between anode (alu brick) and cathode (big old steel hull) and should do the trick. Yes, there's a bit of drag created, but not as draggy as a rusted-through hull would occasion. We have aluminum anodes on the rudder now and are just awaiting the arrival of a pair of aluminum prop hub anodes this week, one to install and a spare.

There's more to this topic of protecting metals, isolating circuits and related topics, some of which I've dealt with in previous posts, And more is likely to come...