Two dissimilar metals that are connected and immersed in saltwater generate an electrical current that initially acts upon the weaker metal. Zinc anodes corrode faster than does aluminum, brass or copper, protecting the harder metals from deterioration. Most watercraft manufacturers provide specifications for the number and size of anodes, as well as locations for each on the hull. Sacrificial zincs are relatively easy to make. As with all molten castings, the work must be done in a well-ventilated area.
Step 1
Fill a metal casserole or other similar cooking pan with clean construction sand, which you will use to make molds for the zinc anodes.
Step 2
Add a small amount of fresh water to the sand and mix thoroughly by hand. Test the consistency of the casting by squeezing a handful of the moistened sand. The sand has the desired consistency when it remains in the compressed shape and is not overly moist.
Step 3
Smooth the surface of the sand with your hand. Depress the surface of the sand to make the molds for anodes using the bottom of a cup, a small bottle or a new zinc anode.
Step 4
Press a 4-inch-long machine screw into the center of each mold as a block-out for an attachment bolt that mounts the anode to the watercraft. Make sure the head of each machine screw is an inch above the surface of the mold. Use a longer screw for deeper molds.
Step 5
Put on your safety glasses and leather gloves. Cut pieces of the zinc-lead compound to the approximate size of the molds using a hacksaw. Cut the pieces a bit larger to ensure that you will have enough material once you melt down the zinc-lead.
Step 6
Light the propane pot and place the ladle on the burner rest. Depending on the size of the anodes and the ladle, place one or more pieces of the zinc-lead into the ladle. Allow the metal to melt down to liquid form.
Step 7
Moisten each mold moderately before casting using a spray bottle filled with fresh water. Ladle the molten zinc-lead into each mold slowly. Fill each mold to the surface of the sand. Allow the zinc-lead to harden and cool completely.
Step 8
Lift the anodes from the molds using the machine screws as a handle. Remove the residual sand from each anode using a stiff bristle brush. Unscrew the machine screws from each anode using a screwdriver.
Tips and Warnings
- Zinc anodes can be larger than specified as long as the anode does not intrude with moving components or obstruct discharge ports in the hull of the craft. Drill the bolting holes larger, if necessary, using a power drill and the appropriate size drill bit.
- Zinc anodes should be replaced once a year. Check the anodes frequently during the first month. Premature signs of corrosion indicate an anode must be larger. Always wear eye protection and gloves when working with metals.
Things You'll Need
- Safety glasses
- Leather gloves
- Zinc-lead block
- Manufacturer's specifications or similar anode
- Metal casserole
- Clean construction sand
- Fresh water
- Spray bottle
- 4-inch machine screws
- Hacksaw
- Propane melting pot and ladle
- Stiff bristle brush
- Screwdriver
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