If the tub isn't yet installed, you might want to have the exterior sandblasted to get down to bare metal. At that point, you can prime, then paint with a good quality exterior or marine grade enamel.

Some people even send their tubs to automobile body shops and have the exteriors painted with the same type of paints used on cars.

I've been through this, and this is what worked for me (but JamesK's advice is better if you want to spend the money.)

I removed the paint with a very vigorous power brush- not your ordinary wire-brush-drill device, but an industrial grade 10" brush mounted on an old 1 hp inline grinder that probably turns at 8,500 rpm or better. It will actually take off some metal as well as all the old paint, and definitely removes rust. It'll remove skin too, and can throw a wire, so be careful and always wear safety glasses, for sure.

Then I cleaned the entire surface with rags saturated with paint thinner.

Carefully masked off the inside part of the tub.

Bought enough spray primer (in cans)to give it two light but thorough coats, and then finished with two coats of my wife's color choice. The spray paint was just an ordinary hardware store grade, if I recall, but higher quality stuff might be worth the cost to you if you can find it. (I used to be able to buy auto paint matched to my car and then put in a spray can. Don't know how they did it or if it's commonly available. It was a little pricey but worked well.)

It was a little bit of a challenge keeping it warm enough in the uneated garage as autumn settled in, but I stuck a light buld under it (it was turned upside down for painting) and that seemed to do the trick.

That's been 10 years now and it still looks like new.

Good luck,

Mark

ps- I did the clawfeet separately, and left them uncolored, but covered with clear acrylic.

This is great advice and gives me an idea of what I am in for, either financially with a snazzy professional job or moving ahead and trying it on my own. Thanks James and Mark!

Aerin