I've had this new exhaust manifold several years in a box, no special packing to prevent rust.
Is there a coating on it that's prevented rusting?
I'm about to start painting; do I use Lacquer Thinner, and/or Acetone, wire brushing, etc.?
If it were yours, what would you do to prep the surface for Rustoleum High Heat Primer?
Probably because no one touched it and it stayed dry enough covered in the box which insulates it.
I have sheet metal in a box in a hot humid Houston garage and it does not rust except for where I touched it in the past.
Like others I painted my new exhaust manifold after becoming a member of the 2 piece manifold club with gray high heat primer. Good so far :-)
How did you prep the surface before painting?
Did you wipe down with Acetone, or possibly Lacquer Thinner?
Did you wire brush?
Did you then cure it by baking?
Please let me know.
Bill, for what it's worth, if you go to VHT manifold paint you only need one can of product. It goes on with no primer, on just clean oil free surfaces. Lacquer thinners is your friend in the clean up.
Hope this helps.
Allan from down under.
What Allan said....I went to a specialty auto paint store and paid $20 for a halfpint of very high temp black for the exhaust manifold. Always brush on paint with cast iron. Just let it dry for an hour then install it and drive your T. The paint'll bake on.
George, mine is in a spray can. I apply 3 coats to make sure I get into a corners. It's dead easy to apply subsequent coats if the manifold is ever taken off. I have even resorted to a freshen up with the manifold on the car when detailing the engine bar for a particular function.
Allan from down under.
Back to the original question, why no rust ? I believe the manifolds are oiled after finishing. At least the new manifold I put on my T last winter was. Smoked pretty good for a few minutes until all the oil burned off. You may want to do that before applying some kind of finish. Cast iron is fairly porous, and a "wash" with lacquer thinner or other solvent may not eliminate the oil as well as "burning off".
Bill my preparation consisted of taking it out of the box, hanging it with a piece of coat hanger, spray painting it and letting it dry for 24 hours. :-)
I prepped a manifold that I cleaned with electrolysis for storage and painted it with lanolin oil from sheep's wool, it dries in about a day or so and looks just like the original cast iron. You could touch it all you like and it would not rust. For painting it would have to cleaned/burned off firstly.