Painting - problem painting exterior doors

I have a metal (w/wood core) exterior door from Home Depot that I wanted to paint. It has white factory finish. I asked guys from HD paint department how do I prep it and they told me to paint latex over factory finish - no priming or sanding needed.

I did just as they said, cleaned surface with rubbing alcohol and painted with 2 coats of exterior latex yesterday. Well, it did not adhere well - if you scratch it with a fingernail, it starts to come off. I decided today to redo the job and just peeled the paint off the door in ten minutes - it peeled off as as stretchy film.

Now how do I do the job right the second time?

The door should be lightly sanded first. I've never heard of wiping a door down with rubbing alchol but have used denatuired alchol occasionally.

What type/brand of latex paint did you use?
Latex paints often take a while to dry hard [some never do] I suspect a lot of your problem stems from a cheap grade of paint. You will find better quality paint at a paint store [they usually give better advice too]

The door should be lightly sanded first. I've never heard of wiping a door down with rubbing alchol but have used denatuired alchol occasionally.

What type/brand of latex paint did you use?
Latex paints often take a while to dry hard [some never do] I suspect a lot of your problem stems from a cheap grade of paint. You will find better quality paint at a paint store [they usually give better advice too]

Thanks for reply, Mark. I did suspect that door needed some sanding, as the surface is quite smooth, but decided to rely on advice of the HD guys. What kind of sandpaper shall I use on it? Is 180 too rough? And do I need to prime or not?

I used satin lustre Behr paint from Home Depot. Shall I use a better paint? What brand(s) do you recommend?

Metal doors have a factory primer applied - no need to reprime. 180 grit will be fine.

I've not used any behr enamels but overall behr doesn't have the best reputation. I would suggest going to SWP or Ben Mooore. They can also match any color you need.