[TowerTalk] Galvanic Protection of Guy Anchors

[Tony Brock-Fisher]

By coating a guy anchor rod with an protective material such as tar, one 
is attempting to prevent galvanic corrosion by removing one of the 
necessary components, the electrolyte (water) in contact with the metal 
of the guy rod. In theory, this sounds like a reasonable approach. as 
long as the coating is complete and intact, this will work to prevent 
galvanic corrosion. However, if there is any small void in the coating, 
water can again contact the guy rod. In this case, there is an area 
concentration effect at the void, which actually increases the rate of 
corrosion at the void. All the current is concentrated in this small 
area. In the case of a zinc coated (galvanized) guy rod, the zinc 
coating will be corroded more rapidly because of the concentration of 
current at this location. Once the zinc is gone, the steel will also be 
corroded.

A tar or other waterproof insulated coating may increase the life of guy 
rods, but must be complete in it's covering of the guy rod. If not, it 
could be worse than nothing at all. The best way to prevent galvanic 
corrosion is by preventing the flow of current in the first place, by 
providing a sacrificial anode that changes the potential of the guy rod 
and diverts the current to the sacrificial anode.

-Tony, K1KP