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I am planning to replace the anode rod on my water heater. Since I only have 19" of clearance to work with, I need to use a flexible replacement.

Looking at the available products, most have segments connected by steel cable. Wouldn't that exposed steel cable act as a cathode - providing a shortened galvanic electrical path to the attached anode material? I would think this would both reduce the protection of the tank and accelerate the corrosion of the anode.

Is this a concern? Is it worth looking for alternatives that do not expose the steel cable?

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  • Have you asked the supplier of teh tank or looked at their website ? Or ask a plumber for a quote and see what they have to say. Also please supply details on the cylinder, anode. Maybe pictures.
    – Rohit Gupta
    Commented Dec 26, 2023 at 23:33
  • @RohitGupta - This is more of a generic question about materials properties and behaviors. Would the answer be any different if I said I had a State Proline (Commercial Grade) model GS6-50-BRT 400, 50 Gal Gas tall tank WH? I already know it has a anode rod separate from the water inlet/outlets. Due to the local city water chemistry, I am leaning towards aluminum instead of magnesium. The real question is the effect of the exposed stainless steel connecting cables, but I think DrMoishe Pippik may have already answered that.
    – T N
    Commented Dec 27, 2023 at 0:54
  • Actually found a model (Everbuilt 3/4 in. NPT X 42 in. 3-Section Aluminum Anode Rod) appears to use bendable aluminum joints instead of steel connecting wire. If installed with care, I think that would make my concerns moot.
    – T N
    Commented Dec 27, 2023 at 2:32

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If the cable is stainless steel, there is a thin layer of nonconductive, adherent oxide on the surface. Though there is sufficient conductivity where a tight mechanical connection breaks through the oxide film, by and large the metal does not create a short-circuited galvanic couple with the sacrificial anode.

It might be possible to further insulate the cable, but it might not be practical. Low-melting plastics are out. PVC might release carcinogens, and PTFE the "forever" PFAS, neither wanted in potable water. Glass fiber can release fragments, a bit like asbestos shedding fibers.

In short, I'd trust anodes from reputable maker.

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Wouldn't that exposed steel cable act as a cathode - providing a shortened galvanic electrical path to the attached anode material?

All that is necessary is that there is some electrical connectivity between the two materials (in this case the important ones are the rod and the tank itself).

In that case, the metal higher on the galvanic series will be attacked at a higher rate, acting to reduce oxidation on any metals lower on the series.

The oxidizing environment of the tank is acting simultaneously on the magnesium, the iron in the tank, and if present the aluminum or iron connecting the segments of the rod. But the rates of reaction depend on the nobility of the metal.

As long as there is still magnesium (or zinc) present, oxidation will happen preferentially there, and at significantly lower rates on any iron or steel connected to them.

Segmenting the magnesium and connecting them by aluminum or steel won't cause any problems.

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