Is it okay to put Special metals Primer on painted surfaces?

[t1ger]

I have been doing my garage doors, I got most of the paint off the first one which took ages and primed it with Hammerite Special metals primer.

There were some bits that I could not scrape off so I sanded down and also primed. I assume that the parts that had the existing paint on will be okay with the special metals primer on top? This would give me a unifrm base colour to work from.

On my other door, I am thinking of leaving more of the existing paint on. I still have some of this primer left and was going to paint the whole door with it, after removing the flaky paint.

There is a lot of flaking, quite small flakes. Will the currently unflaky parts continue to flake off after repainting? Should I just take the hit and scrape all the paint off or just sand it down?

As an aside, the garage door is a Garador Mark 2c and has a galvanized top half but the bottom half was not galvanized, is that normal? Is it okay to put the special metals primer on this non-galvanized part. It doesn't have any rust.

Thanks for your advice.

 

[TheDec]

If I were you I would forget the special metals primer, try and remove as much of the existing paint as you can and apply one coat of zinc phosphate primer and then two coats of Dulux Trade Metalshield. This system is available in both gloss or satin.

Dec