[TowerTalk] Tower Leg Maintenance

[K8RI]

On 12/6/2011 4:39 PM, Frederick Vobbe wrote:
> I think most of us with older towers have, at one time or another,
> painted or at least removed rust starting on the outside leg of a tower,
> and repainted it.
>
> Has anyone done anything to the inside of the leg?

Pouring sealant in from the top is a bit "after the fact", BUT the old 
aircraft construction sprayed linseed oil for rustproofing into the 
steel tubes that made up the strength of the fuselage.

Were I going to recondition an old tower like the 25G or American Steel 
(BTW the American Steel towers of which I have used many) are no where 
near as strong as the 25G. I don't know what they are coated with but 
it's definitely not hot dipped galvanized.  I would get some of the 
steel brushes used to clean the inside of copper pipe joints before they 
are soldered. Use brushes of a size that are a snug fit in the tower 
legs.    Using a 1/4" to 3/8" rod at least as long as the tower section 
drill a hole at least a half inch deep  into the end of the rod.  1/4", 
5/16", or 3/8" steel tube might work.   Half as long will work and might 
be easier for some to handle.  Cut the handle off the brush leaving 
enough of the twisted wire to fit into the end of the rod and using 
either a set screw or solder...or brazing, fasten the brush to the end 
of the rod.  Chuck the rod up in a variable speed drill and run the 
brush up and down through the tower leg as many times as it takes to get 
it clean. This may help to spot any  rust that might be in there.  If 
you get a lot of rust out, it'd probably be best to just pitch the section.
Once the legs are clean inside, a flashlight should reflect off the 
inside making them look almost like the inside of a shotgun barrel.
I'd then use a sprayer with Linseed oil or a spray can of LPS2 to coat 
the inside of the tower legs thoroughly.    This will be messy.  LPS 2 
has enough solvent in it to penetrate into tight places but will leave a 
grease like coating for protection.  I've seen it used to 
rustproof/corosion proof portions of cars or aircraft.

A pump up sprayer could be adapted with a tube to run the spray nozzle 
through the length of the leg getting a much better coating. OTOH the 
sprayer probably will not be good for much else afterwards.

I'd be more inclined to clean the tower legs and then give them a good 
coating of the cold galvanizing inside and out with the rustproofing 
internally a few days later. What ever you put in there is likely to 
eventually wash out.

Just remember that reconditioned old towers may have some weak spots 
that don't show.   There is a tool  (Ultrasonic) for checking leg 
thickness. I don't know where you'd borrow one and they are most likely 
expensive. We used to use them to measure tank and pipe wall thickness 
down to a few thousandths of an inch IIRC.

73

and good Luck

Roger (K8RI)