Here's a chart that should get you close. If the powder coater doesn't have a clue about the different powders I'd avoid them. Like I said, we never cared about all the factors as long as the color was right, but at least we knew there were other factors if the situation dictated it.
There are a few different powders. You can get a commercial powder that is made for high impact resistance and you'd be close to 100% okay. I'll be honest that nothing is like that ceramic coating that comes on appliances, sinks, etc.
IF it is cured correctly and IF the correct powder is used...
You can powder coat anything that will take 400* for 20 minutes (plus the time it takes for the part itself to get to 400* and cool off afterwards).
If you can't get a charge through it for the powder to stick you can heat the item up and shoot it hot so the powder melts and sticks when it...