What Primer on a Carb.?

I painted the carb on my 8N Ford Tractor about 6 weeks ago. Primed it first with regular grey metal primer (Rutoleum0 in a rattle can, then next day painted with New Holland Ford Red, and then waited for a day and put the carb in the wife's oven for 4 hours at about 150 degrees. All looked good for a week or so. Then the paint started to lift away like gas was getting into the primer and releasing it from the metal.

What did I do wrong, and how should I paint a carb so it doesn't have paint "run" or "lift?"

Bob

[Harry]

If all else fails, blast it clean and dip it in phosphoric acid. Followed up with that 150 degree heat it should be pickled with a nice gray metallic finish.

Carbs and fuel tanks have to be the worst place for paint to hold up and it might be it was the primer that failed. I've had good luck with painting over top of the phosphoric treatment. No primer colors to show through when a scratch or abrasion comes along.

Thanks Harry for reply, but where does one look for the acid? A paint shop? or????

Bob

[Harry]

I get mine at Home Depot. An automobile paint distributor should also have it.

Do a SEARCH here on PaintShop for "phosphoric acid" and you'll find other posts.


http://www.enginads.com/paintshop.cgi/read/37107

Other names of phosphoric acid products include: Ospho, MetalPrep, MetalEtch, Docspho, etc.

For those learning about Ospho, look at the ingredient list on Pepsi and Coke. Included ingredient is phosphoric acid.

I don't think it is the primer. I suspect you have a small fuel leak. Gasoline will lift most any fresh paint, baked or not. The only one it doesn't seem to bother is the two part urethanes, but they are expensive. I have also had good luck coating frequently fuel wetted areas with aerosol clear shellac after painting. Shellac is not soluble in petroleum base solvents. This only helps if gasoline drips on the area. If it is leaking at a joint, it tends to get under the paint where the paint ends. Also, keep your carb paint thin with just one or two coats at most after priming or phosphatizing. Be careful using heavy strength phosphoric acid on any zinc or pot metal parts.

Thanks everyone for the help.

Bob