Painting Problems with Oven Curing

[londonboards]

I'm trying out some engine paints. I want to decide on a paint to use on the engine and all the black part. Then I can show the powder coating guys the exact shade and satin type finish I want so that they all match up.

I painted this caliper with VHT white undercoat and then a satin black top coat caliper paint. I waited for the wife to go shopping and cooked it for 30 minutes at 200 deg C.



but it bubbled up on me on the flat machined surfaces. The white undercoat was not affected.



I am wondering if I should have cured the white undercoat before spraying the satin black.







Other than that, I really like the finish it gives. It became more satin through the curing process and is almost like the 35 year old part from my bike. LHS is painted one. RHS is the old bike part.

Greetings

[Agemax]

i use the same VHT paint on my exhaust, always used it. i have never used the undercoat.just made sure the surface was spotless clean but roughed slightly.
run over it with a hot air gun,(not your hairdryer,(or your wifes!)) which gives it a sort of pre harden(!). then cure it properly on the running bike.
never had a problem with it flaking or not adhering properly.

[Frank Z.]

A guess at what happened:
The undercoat hadn't dried/cured enough before the topcoat was applied, effectively trapping in moisture... which had to find a way out during the oven cure stage... resulting in the bubbling.

[rustybronco]

Per VHT

http://www.vhtpaint.com/products/flameproof/

Off the Vehicle

Paint must be completely dry before curing
Heat to 250°F (121°C) for 30 minutes
Cool for 30 minutes
Heat to 400°F (204°C) for 30 minutes
Cool for 30 minutes
Heat to 650°F (343°C ) for 30 minutes

Caution: Do not exceed the temperature of the least heat tolerant component or the base metal

http://www.vhtpaint.com/products/caliperpaint/

Bake at 200°F (93°C) for 1 hour.

[still_bluenoser]

I've used the black on brake parts with only a well curred coat of zinc chromate primer underneath. Never had an issue.

I'd say its definately the undercoat causing the issue.

[83_450E]

Looks like top layer flashed too fast over it all and trapped in solvents that gassed out.

Paint was not completely dry before you gave it the heat.