Why do water heaters need an anode?

[TSN79]

I've read about water heaters needing anodes, but I don't really understand why. The objective is that the anode should protect the tank by "attracting" corrosion, isn't that right? But aren't water heaters usually made of stainless steel anyway? Around here most water heaters don't have an anode, and if they do it's considered a special case, like if the water contains salt, which I guess attacks the tank even if it is stainless steel...? I also read that the anode is sometimes made of aluminium, which doesn't even corrode in the first place - how does that work?

 

[anorlunda]

All corrosions are not alike. Galvanic corrosion is caused by small electrical currents. The sacrificial anode doesn't attract corrosion, it serves as a source for the current so that it is eaten rather than the tank. We sacrifice the anode instead of the tank. Zinc is an excellent anode, but aluminum is also good.This article explains more.
https://en.m.wikipedia.org/wiki/Galvanic_corrosion

 

[Noisy Rhysling]

The USN has zinc anodes all over the place. Inspecting and renewing them is part of the Preventive Maintenance System.

(Yeah, PMS.)

 

[phinds]

The USN has zinc anodes all over the place. Inspecting and renewing them is part of the Preventive Maintenance System.

(Yeah, PMS.)

So does that mean the maintenance techs get cranky?

 

[Tom.G]

So does that mean the maintenance techs get cranky?

No. Just cranked.

 

[Noisy Rhysling]

We've already done the good jokes, folks.

 

[Davorito]

For health concerns, I'd go with zinc anodes way before aluminium anodes.

 

[Noisy Rhysling]

For health concerns, I'd go with zinc anodes way before aluminium anodes.

Expand on that?