Painting metal siding advice please

[TexasTimbers]

My dad has given me a boatload of ag panel and they are all in this shape. What do I need to do to prep the surface prior to painting? I do realize at best I will only be able to make it look decent - not good, and probably have to repaint in a few years. But it is going to be used for air drying covers on a slight picth and will not be seen. *Some* of it will be used for actual siding so I would like to make it look as good as possible. I have no experience prepping and painting metal like this.

[beenthere]

Are we looking at rust  bubbling through the paint, or undercoating showing through a thin top coat of paint?

Was it tight stacked causing the problem, or was it on a roof or as siding? 

[TexasTimbers]

Yep it was deadstacked about 15 years ago. It's a wonder it isn't worse. i'll try a close-up

[tcsmpsi]

Should wirebrush anything loose off (flaking paint, loose rust).  Not to worry about the 'stable' rust.  Treat with phosphoric acid, the paint.  Several companies produce the solution for treating metal, some specifically for similar application as per your needs.

Last I checked, Home Depot has a pretty good product for that.  I have used Ospho for a looong time, but picked up a few gals. of HD's product a while back.  I like the Oshpo better, but the HD stuff will work. 

Get your siding ready before applying the phosphoric, let the phosphoric do its thing (you can tell when the iron oxide has turned to iron phosphate), then paint and be thee happy.   

[Murf]

For my two cents worth, wipe it clean with some thinners, thin out your favourite flavour of rust paint, and spray it just the way it is.

If it took 15 years of dead stacked time to create that little bit of rust, you won't live long enough to see any serious rust develop once it's exposed to the sun and the wind to keep it dry and clean.

[logwalker]

I am going thru the same thing. I use the Ospho or any phosphoric acid prep as it converts the rust and makes it a good painting surface. It is pretty easy too. Wire brush first and brush on or spray with the acid and rinse a 1/2 hour later and go. Joe

[leweee]

http://www.gemplers.com/icatalog/2007_Master/iCatalog_Spreads.aspx?Page=472 ;D