View Full Version : Best Paint for a Tower?
07-02-2003, 02:24 AM
I purchased a used Rohn-6 30' steel tower from a fellow ham. It's in great shape structurally, but has a few rust spots. I'd like to paint the tower and I'm looking for advice as to what paint would be best to use. My thoughts are to use spray Rustoleum primer and then a few coats of spray Rustoleum gray. Am I on the right track here? Can anyone perhaps recommend a better primer or paint to use? I'd like to be sure the paint holds up, wont flake off, and prevents any rust "bleed-thru" in the future. Your thoughts? Thanks!
07-02-2003, 02:34 AM
Wire wheel the rust off, or use one of rust conversion solutions before you even push the button on a spray can. Make sure you actually get it off, and don't just burnish it.
If you don't, it will keep going.
Then prime it well, and paint any color you like..
07-02-2003, 03:55 AM
You did not say, but is the tower originally galvanized? Does it have a silvery-grey metalic Zinc coating on it? If it does, then the best solution is to replace the missing Zinc rather than paint it. A welding fab shop can do this for you, usually pretty reasonably. For small spots they can sandblast and plasma spray on a molten Zinc coating. For more extensive recoating, they can send it out (or tell you where to take it) for hot dip galvanizing. This may take a while, as they may have to collect a truckload before sending it out if you don't have a local galvanizing house.
Paint, or rather, oil based paint, does not adhere well to Zinc. Reason: Zinc is an "active" metal in the chemical sense. In the presence of a little moisture it forms a fairly strong base (caustic) compound. Like Lye, this Base combines with the oil in the paint in a process called sapponification to form a soap at the boundry between the zinc and the paint film. Soap is not a great adhesive. Particularlly in the presence of water. Paint peels off, usually enthusiastically and in large sheets.
There are specialized Zinc-rich primers, available at Marine suppliers (real ones supplying commercial fishermen or ships) that will work well on galvanized hardware. Look for asphalt-based Zinc-rich "Cold Galvanizing" compounds. Rust-Oleum and similar spray paints are not very satisfactory around Galvanizing. They want nice shiny bright bare iron in order to do their best. Oddly enough, some exterior latex paint, being water based rather than oil based, does seem to adhere rather well to galvanizing. Unfortunately it "breathes" water vapour (a good thing on wood and concrete) and so does not protect bare ungalvanized iron very well. I'm told that there are some exotic ployurethane, and epoxy based paints that are good, but I don't know much about them. Maybe someone who specializes in painting iron structures, water towers, etc, could help out with a suggestion here.
07-02-2003, 04:19 AM
Do not be afraid of what I write, these are just ideas...
I've tried having a look at Rohn web page, but it goes too slow here. I also could not find your tower, neither what treatment they do before delivery. I only had a small look at their G series. So, various points that may not apply in your case. This is just my opinion, do not rely on it w/o counter-check....
What is the general finishing ex-factory? Is it just anti rust painted, or is it galvanized. Is it electro galvanized or hot dip galvanized?
Are the main structures made of pipes (like G series)? If not hot dip galvanized, then you might have a rust problem inside. Have a look if you can. If yes, then there is not a lot of choice. If the damage are limited, you would need a degreasing and acid cleaning, after what you would need to re hot dip galvanize (electro galvanize does not work deep in the pipes). This is a very extreme case with extreme solutions. Unless, if you know an easier way to work inside the pipe, try it anyway.
For only outside damages, you can easily rework by hand by a lot of standard means, but be sure having all very well cleaned and avoid touching it with natural sweat on hands or greasy hands.
Now also before re-assembling, clean, and rework all the parts that will have frictions (fitting pipes, bolts, treads,...) Even well protected, some fittings (if not in stainless steel) will easily rust. And before assembling, grease all in good quantities.
Again, do not get stress about inside damage, I believe they have a certain technology standard to prevent this, but just have a look.
07-02-2003, 05:14 AM
I feel that KA4GEH is heading in the right direction
here. # #
The best product to use on your old Rohn #6 is
Rust-Oleum "Cold Galvanizing Compound" #7585,
OR Rust-Oleum "Bright Galvanizing Compound" 7584
OR an equal quality other brand product.
This is NOT a paint, but actual zinc dust that protects
against rust as good as hot dip galvanizing, But is not
as resistant against scratchs as Hot Dip galvanizing.
This stuff is used by the tower pros on commercial
towers for touch up.
There is no question that cleaning your tower and
having it "Hot dipped" galvanized is the best, I expect
that the cost to do so will far outweigh what it is
worth. In fact, I bet you could buy a good used
Rohn 25 for what that process would cost.
Be aware that the old Rohn number 6 tower has been
out of production for many years now, And is not
capable of very much. I would not spend too much to
fix one up......... #
The "Rust Converter" type products I have seen do
indeed stop rust, BUT they also insulate the steel!
Something you do NOT want on a tower. You want good
electricial contact between tower joints, and any
antenna brackets, etc bolted to the tower.
07-02-2003, 07:01 AM
"You want good
electricial contact between tower joints, and any
antenna brackets, etc bolted to the tower. "
Yes, in that case, you may have problem with the grease I suggested, but I do not know up to what level. I would at least grease the treads.
07-02-2003, 12:58 PM
Thanks for all the input. From what I can tell, the Rohn-6 was discontinued some years back and I can't seem to find find any actual manufacturer info on it, but I'm told the tower was hot-dipped galvanized. I only paid $30 for it and the rust I see looks to be just surface rust. All in all the tower appears to be structurally sound. I'm only going to put a Diamond D-130 discone at the top, a J-pole and a couple of Scantennas hanging off the sides, so there won't be a whole lot of weight going on it. I also plan on converting it to a hinged base so I can walk it down for service or changes. When it's upright, it will also be bracketed to the house at about the 8' level to provide some extra stability. This is my first tower, so I appreciate the advice and information.
07-02-2003, 03:11 PM
You DON'T want to start painting a tower if you can avoid it! The Rohn 6 was hot-dipped galvanized to start with. Use of one of the spray galvanizing compounds as mentioned above is probably the best thing to do.
If you paint a tower, it is going to need to be repainted in a very few years. Also, rust is more likely to form under the paint. Thus, just clean it and then apply one of the galvanizing sprays. They don't cost much more than an ordinary can of spray paint and do a very good job.
Rohn 6 was replaced by Rohn 25 for most applications. It has been several decades since it was made new. However, if properly maintained and installed, it will last for several more decades.