I wouldn't think powdercoat would stick to aluminum because of the need of an electric current.
In powder-coating the "paint" is "Thrown" onto the object via a
static electric charge from the "gun" to the object to be painted, not a fixed running electric "current" ( as in the E-coat paint system, where items are immersed in a tank with an anode & the object to be painted is the Cathode similar to electroplating.) it would work fine regardless as Aluminum is a metal & the third best conductor of electricity next to Copper & Silver.