Top coating primer

[geraldmorrissey]

I'm using Stits EP 420 epoxy primer. My biplane friends insist I need to use a topcoat over the epoxy primer on my steel parts. I have had good luck over the years with just a coat of primer over properly prepared steel. Do I really need the protection of a top coat on steel? PPG Concept LV acrylic urethane is the recomended product. Expensive, but if it's worth it, my baby gets it!
Cheers
Gerry
Patrol #30

[ScottS]

If you put it on to thin, I’ve seen rust come through.

Scott
Patrol

[Steve W]

Primer is a bonding agent between the metal and the topcoat which provides the protection. Its not reliable to prevent rust on steel on its own. I haven’t seen a manufacturer list their primers as an end all for corrosion protection on steel. Usually says to topcoat. My 2 cents worth….

[alaskabearhawk]

What he said...topcoat.

[jaredyates]

I saw some rust in places on our first plane where the ep420 was the only thing on the steel. Could this have been an application problem? Of course, but next time I will top coat.