No, I don't think so for several reasons.
A magnet will probably be ruined if you bake it at 400F, most magnets lose their charge somewhere maybe 200-300F I think. I used to know some of the different type and temps but forgot now. Anyway you'll still need a hanger for baking!
Other problem I am pretty sure of is the poles of the magnet will ruin your coating job anyway. Since you need a negative charge on the part and the powder is a positive charge comming out of the gun the powder sticks to the part. So what happens if you stick a magnet to the part? The positive pole of the magnet will probably blow away the positive powder being sprayed at the part.
Likes repell.
Other thought is the negative pole of the magnet may suck up all the powder that might make it to the part, opposites attract, and the pole of the magnet is probably stronger than the part.
Another thought is surface area. A magnet stuck to a part will be worse than a little clip for the uncoated hanger area defect.
As I mentioned heat ruins magnets, you also won't be able to remove or move the magnet once part is coated with all that loose dust without ruining the coating on the part so you would end up having to bake the magnet with the part rather you want to or not.
I did give this a little thought already before if your wondering. I have some VERY strong NEO magnets, can barely seperate them by hand and an accident with them could break a finger, not cheap toys! I have smaller strong ones also.
I do allot with magnets and some parts I want to powder coat use these magnets. What I've decided is I will have to mask off the area where the magnets are bonded to the part and powder coat first, then bond the magnets to the parts. This means I have a stack of parts that will not get coated cause the magnets are bonded on already
