Paint flakes off engine

[Romaniac]

Im ina bit of a predicament, as I just finished painting my engine, and the paint is already flaking off. The thing is, i went through the proper prep to make this engine perfect but now its turning to garbage.

I went over the whole engine with a wire wheel to grind off old surface rust and old flakey paint
Sanded it down
Degreased it very tediously
Sprayed rust converter on rust spots
Sprayed the whole thing with 2 coats plastikote engine primer
Waited 3 hours then hit it with engine enamel
Let it cure for 48 hrs

Where did I go wrong?! I really took my time on this and its not coming out how it should

 

[Romaniac]

The paint just flakes off with a screwdriver 🙁

 

[CWPottenger]

My guess is the primer and enamel didn't bound. Engine Enamel typically doesn't need a primer.

 

[Romaniac]

My guess is the primer and enamel didn't bound. Engine Enamel typically doesn't need a primer.

A point i forgot to add is when the paint flakes, it flakes all the way down to the bare metal.. and only on certain spots, mainly the machined surfaces. Is there a way to remedy this?

 

[565bbchevy]

I have never primed an engine before painting it and never had an issue with paint coming off, just a thorough cleaning and a few coats of Duplicolor engine enamel and then I would go over it with engine enamel clear.

 

[Romaniac]

I never heard of primer hurting a paintjob before..
What steps should i take now? Scrape the whole paintjob right off, paint strip it, or just look for parts that flaked off and spray right over them again?

I think the problem might be the old paint that was on the engine.. It might have a bad bond to the metal, so when i sprayed over it with the new paint, the old paint softened or lost its etch. Thanks for the input

 

[81msw79]

was the primer you used a "etching" type primer. if so the primer could have attacked the rust converter paint you sprayed first and caused it to peel down to bare metal.

 

[Romaniac]

was the primer you used a "etching" type primer. if so the primer could have attacked the rust converter paint you sprayed first and caused it to peel down to bare metal.

Im not sure. Its plastikote engine primer, and it didnt say anywhere on the bottle if it was etching.
The rust converter converts the rust to primer, its not a paint.. Im not sure what caused the paint to peel.. Any remedies?

 

[Carlola]

You will have to remove all the paint currently applied. Sorry, but there's just no way to fix it after the fact.

As far as the "why?" goes...

You say you wire wheeled off flakey paint, does that mean there was still old paint on the block you painted over?

Did it seem to peel more in the areas you applied the rust converter?

Did you use a heat gun or hair dryer to cure the primer/paint?

What kind of engine is this? Year specific if you know. Post the casting #, if it is a problem with spraying over old finish, we should be able to determine what it was with a quick search. Do you know if the previous finish was factory? If the old finish was a laquer, enamel is hit or miss on top, regardless of prep.

If the prep was perfect, there is a very small chance you just got a bad batch of primer. Happens, though rare. If you aren't on a tight budget, and have the bare block, hot tanking would be a lot easier than scraping/grinding everything off, would also leave a primo surface for repaint.

 

[Romaniac]

You will have to remove all the paint currently applied. Sorry, but there's just no way to fix it after the fact.

As far as the "why?" goes...

You say you wire wheeled off flakey paint, does that mean there was still old paint on the block you painted over?

Did it seem to peel more in the areas you applied the rust converter?

Did you use a heat gun or hair dryer to cure the primer/paint?

What kind of engine is this? Year specific if you know. Post the casting #, if it is a problem with spraying over old finish, we should be able to determine what it was with a quick search. Do you know if the previous finish was factory? If the old finish was a laquer, enamel is hit or miss on top, regardless of prep.

If the prep was perfect, there is a very small chance you just got a bad batch of primer. Happens, though rare. If you aren't on a tight budget, and have the bare block, hot tanking would be a lot easier than scraping/grinding everything off, would also leave a primo surface for repaint.

Yes, I painted over old paint which was flaking in some places.
It was enamel, and not factory.
I didnt use a heat gun to cure the primer, didnt know it had to be done ahh.
This is a roughly 5-10 year old small block chevy 350.
I think it peeled where i applied the rust converter, yes.

Im on a tight budget, so thats out of the question. I dont think Im willing to do either boiling or scraping the paint off. I just ran over the whole thing with a wire wheel and got the new flaky paint off, and this time sprayed straight enamel. If that flakes off too, ill look into using a different brand of engine enamel (or is laquer better?) like duplicolor because im not pleased with this plastikote stuff..

Thanks for all your feedback again. 🙂