Topic: Paint repelling surface?

[Bodi]

I've done a lot of painting and never seen this.
I'm trying gloss black Rustoleum epoxy appliance enamel, hoping to do a tank with it. I painted a lawnmower tank as a test.
This small tank was prepared by removing the old paint using a wire wheel, sanding with 100 grit then 600 grit, washing with soap and water, extensive rinsing, drying, wash with isopropyl, final wash with acetone.
After drying the paint went on quite nicely except...
Some spots repelled the paint, it just jumped back from the metal.
As far as I know no silicon was ever used on it, and the multiple different washing should have taken that off anyway?
It looks like a silicon problem but I can't figure how it got there.

Taking pics of shiny black paint is hard, but this shows sorta what happened - the silver parts are bare steel:



Any ideas on how to avoid this?

And: the epoxy paint, after curing one week, seems fuel-proof.

[BomberMann650]

Primer coat first?  Just a guess.  I've never used rustoleums appliance enamel.

[Bodi]

The can says not to prime it. Recoat is odd, within 30 minutes or after 1 week.
I've seen similar spots using "normal" spray paint where silicon or some mold release agent was involved, but after an acetone wash the problem did not repeat.

[Lostboy Steve]

I've done a lot of painting and never seen this.
I'm trying gloss black Rustoleum epoxy appliance enamel, hoping to do a tank with it. I painted a lawnmower tank as a test.
This small tank was prepared by removing the old paint using a wire wheel, sanding with 100 grit then 600 grit, washing with soap and water, extensive rinsing, drying, wash with isopropyl, final wash with acetone.
After drying the paint went on quite nicely except...
Some spots repelled the paint, it just jumped back from the metal.
As far as I know no silicon was ever used on it, and the multiple different washing should have taken that off anyway?
It looks like a silicon problem but I can't figure how it got there.

Taking pics of shiny black paint is hard, but this shows sorta what happened - the silver parts are bare steel:



Any ideas on how to avoid this?

And: the epoxy paint, after curing one week, seems fuel-proof.

I had that issue with the epoxy hard paint a few times on fork lowers as well. If you strip them again, try misting on an almost translucent coat. Let it dry. Then do a second equally thin coat. Let that dry as well. The final coat can be "wet". This usually works for me.

[CB650CPastor]

Yeah - definitely looks like some sort of surface contamination. I would think your cleaning process would have removed it though. Sometimes metal that has had oil on it for years can be hard to get clean... The metal can almost seem to 'weep' the oil even after you clean it off.