Personally I'd find something else. Something more predictable. Coat hangers are typically made from scrap metal and the composition can vary wildly from one to another. This makes testing worthless unless you are willing to analyze every individual piece. Which under certain circumstances can be worthwhile...for example...

At the height of the Cold War the Soviets were building yet another enormous long range bomber. Our agents had supplied all the deatails but one...the metalurgy and weight of the airframe...which is a figure necessary for calculating the bomber's range and determining it's threat level. This final piece of the puzzle was provided unknowingly by the Soviets when a quote by the director of a manufacturing plant in Siberia appeared in an article in one of their own state-controlled newspapers. In it he bragged how proud he was that his workers were using the scrapmetal from the airframe of the people's newest & most glorious bomber to make one of the factory's most humble but useful products...(you guessed it)...coat hangers. American agents snagged a few from that plant...we confirmed the alloy, calculated the airframes weight, accurately predicted it's range within just a few miles and determined that, despite the Soviet's bragging, it did not pose a substantial threat. All thanks to two things...loose lips...and scrap metal being the primary stock for coat hangers.

Ain't life a wonderment?

KK, that's kind of what I was thinking. But, at the rate that those things reproduce, I figure they are almost a renewable resource!

I can still use them and cover with hardware cloth, right?

Thanks for the history info!

I think that coathangers would be fine if you apoxy coat them and keep away from chlorides. The hangers could cause spalling within 10 or so years when they start to corrode, if you dont seal them and since they will be "close" to the surface.
Tango, that was quite interesting. I love trivia like that.
Jo

Epoxy coating hangers would completely elliminate the virtue of using them in the first place.
Most good hangers are coated to protect against damp clothing.
I suggest you throw them suckers out in the rain for few days.:)
Use the ones that don't rust for your critical armatures.

Actually, that sounds like a plan, to use coat hangers and coat them with epoxy. I have a bunch I was going to toss. And they are the right thickness for smaller projects. I also have a few small coils of electric fence wire, will have to get that out to use, too. Was looking for something I could shape to use for loops for hangers embedded into smaller leaves. Thanks for the idea.

If you are going to use Epoxy I would like to say: GRIN for Tango.
All epoxies are not created equal.:)
Most of them are designed to cure crystal hard and will crack when you bend the wire exposing the metal.
An Epoxy like G-2 used in the boating industry cures to a flexible hardness allowing you to bend the wire with no cracking.
It an inexpensive epoxy as well and worth looking for.