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Sacrificial anode on an above-ground steel structure?

Hello;
I've been trying to figure out if a sacrificial anode can be used on an above-ground, static steel structure to help prevent rust. I've been reading that sacrificial anodes are used in situations where dissimilar metals are surrounded by an electrolyte like water or soil, which is different from a steel structure sitting on the ground. Our products are A36 HRS P&O;, then powdercoat painted.
Each painted member is bolted together using a SS bolt/nut.

Inevitably, the painted surfaces get scratched and start to rust. Is it practical to use a sacrificial anode on the structure to prevent the rust? What if I ran a grounding strap from the steel structure into the ground, and close by it I buried a sacrificial anode, and ran a strap from the anode up above the ground and connected it to the steel structure? Would that simulate the electrolyte environment for the circuit to be completed, and then the anode would corrode instead of the steel structure rusting?
Thanks for reading,

-Eric

Eric Golden
skate park ramps - Joplin, Missouri, USA
2003

There are experts on this subject, and hopefully one of them will answer you. In the meanwhile, I will mention the general principle that galvanic corrosion and galvanic protection require both a metallic path and an ionic path (wet path). Galvanic protection obviously works on ships; it fails on cars because the vulnerable metal of the car can't be connected to a sacrificial anode by a constantly wet ionic path.

The containment structures of at least some nuclear power plants are protected with sacrificial anodes, however. Apparently there are some areas that are wet enough that the protection works, and when one is working with a nuclear power plant the cost of sacrificial anodes is probably insignificant.

What you probably want to consider, however, is the use of galvanized metal. That way, the protection offered by the zinc is right where it's needed, and galvanizing does deter rust.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003






Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey