Jake

I usually ask the paint suppliers what primer they recommend. They should have the best idea. On my last job they supplied "Haymes Galvanised Iron Primer". It was the first time I had encountered a primer specifically for galvanised surfaces and I hope it does the job. I have always been worried about any paint being able to stick to galvanising.

Please let me know how it all goes.

Good luck.

Peter

Jake,

I like to spray my own paint, rather than use rattle cans, though for the 90% zinc stuff it probably doesn't really matter that much. Be sure to let that stuff dry at least overnight, and preferrably two full days, before you paint over it. It has very little binder so it needs to fully polymerize before anything goes over it or it weakens it.

For the intercoat primer, I like a good iron oxide primer, either epoxy-based or acrylic enamel automotive paint. Expensive, but worth it. Once that is dry, whatever you put over it will stay, as long as you pay attention to your compatible chemistries. Some paints don't work and play well with others, if you know what I mean. That's one reason I like to stick with automotive paints for the most part, as they tend to play nicer with each other and the manufacturers are pretty decent about telling you what goes well with what. With specialty paints like the iron-rich stuff Peter used that is intended to rust, you should definitely talk with the manufacturer's technical advisor and find out what they recommend as a primer for it. I suspect you could have intercoat adhesion problems if you don't do the right thing.

Some galvanized metal primers (the ones intended to prime galvanized metal), are made with an etchant included to cut the "sheen" on hot-dipped galvanizing so that the paint will adhere. You don't want to use on of those over most of the 90% zinc primers. The 90% zinc primer has a very "open" or "toothy" finish that is designed to be receptive to topcoating and the etchant in the primer for galvanized metal may penetrate through it and affect the steel underneath, causing problems down the road a couple of years.

When in doubt about relative compatibilities of different paints, remember that it almost never hurts to use an "intercoat barrier." This is a product that is so benign that it doesn't affect any paint and creates a barrier between different paints. Auto paint stores sell to people who want to put lacquer over enamel and don't want to get sand-scratch swelling due to the hotter solvents in the lacquer burning the enamel.

I hope this is of some value to you. I think you're definitely doing the right thing to take control of your finish work yourself. You may not actually enjoy the work, but you'll definitely enjoy the peace of mind you get knowing that the painting was done correctly and on-time.

Part of the work that we do is to replace failed paint coatings on outdoor sculpture.

Current best practice is to air abrade to "near white metal" finish, removing all mill scale.

Coat with a high build epoxy primer.

Top coat with either a catalyzed urethane and a UV resistant clear coat, or a silicon alkyd.

The choice is based on the type of environment and maintenance that the sculpture will be expected to receive. The silicon alkyd can be touched up easily and the urethanes must be sanded first.

Sacrificial zinc coatings are not used.

You can see some work at: www.mckaylodge.com

Best regards, Tom