Metal primer

[steamlaser]

I recently bought some grey undercoat metal primer for my traction engine.( The paint is water based.)
I undercoated the cast hubs of the rear wheels and after a few hours drying, little bits of rust are showing through the finish. Before I start on the tender and other major parts I need some advice.
1. Am I using the right sort of undercoat?
2. Does the primer need to be oil based?
3. I rubbed down all surfaces prior to painting. Does one need to remove every speck of rust before applying primer?
4. Does one need to use a primer that chemically etches and protects the surface?
5. I know it is a bit cold to do painting, but it says on the can that it will be effective at 10 Deg C and the paint did dry in four hours as stated on the can.
Your advice will be greatly appreciated.

[ejparrott]

Etch primer is only required on non ferrous parts. Personally I wouldn't use water based paints. I try not to paint anything important in anything less than 16*C

[theartfullcodger]

I paint all my models with 2part etch primer non ferrous & ferrous 2 part epoxy is used in the motor trade as it's water resistant & prevents rusting.

[Jim]

I'd just add that for parts that are subject to heat such at the chimney I used a heat resistant enamel from an Automotive shop and on the advice of a former paint technician applied it directly to the metal without any primer. The result is a lovely glossy heat resistant black that has lasted and lasted.

The first time I painted the chimney I used a metal primer then a top coat of automotive heat resistant spray gloss black and all went well until on a particularly hard run the paint blistered and flaked! It was then that I sought the advice of our club boiler inspector, a retired paint technician who explained that it was the primer that gave way in the heat and to apply the heat resistant enamel directly to the clean metal. Not had any problems since and I have used the same method on the Britannia's smoke box.

Jim

[fostergp6nhp]

Water base paint😱, I can’t abide the crap, get proper paint, Craftmaster have a good reputation.