Found Excellent Battery Compartment Black Paint At Wal-Mart

I've been using Rustoleum Stops Rust Hammered when I redid mine. If that fails your choice will be my next stop.

I’ve never tried your battery acid experiment, but agree this is some very tough paint!

I agree - been using this product for several years (Home Depot stocks it);
Has high solids and if the surface is prepped properly then it sticks and
you end up with a surprisingly tough paint.

I use it to paint the TH chassis, wheel wells etc. I just painted a utility
trailer with good results.

I've also used to to paint the trunk and floor-pans of an older cars - still
looks good.

I also use a High Temp Paint from HD - it has high solids and covers really well

Paint technology has come a long way in the past decade - just look at all the
various paints on the HD shelves - there's something for everyone..

Thanks for the advice. I need to paint my battery tray. I'll try your recommendation.
I like cheap fixes.