Repainting an old corrugated galvanize steel roof

I am repainting a corrugated galvanized steel roof about 20 years old which was painted about fifteen years ago. The paint is now flaking off in places leaving the original galvanizing in good condition. It is to be water blasted which I understand will remove loose old paint but will leave firmly adhering paint so I will have a mixture of old galvanizing and firmly adhering old paint. I would like to use a roller application using water based (acrylic?) paint for ease of application. Presumably I will need to give one coat of primer and one of finishing coat. Can someone tell me what paints to use for the primer and the finishing coats.

Thank you,

Primer for Galvanized Metal

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For home use, you require a special primer over galvanize. This used to be a zinc chromate based primer, but that has been restricted for several years in the US. Talk to 3 different paint stores, one of them will give you an answer that can be believed. Yes, you can roll that also.