I just thought I'd add to this
Powder coating is fine in and of itself. It's the heat involved. Some places use high levels of heat, and heating an alloy ages it. Generally it makes them stiffer and less flexible. This is bad for wheels as if they cant flex a little under load the will crack at the hardest points, usually where the spokes join to the outer rim.
Another example is filing cabinets believe it or not. They get away with a thinner steel by heating and powder coating it, to make it stiff enough and strong enough for purpose, making them nice and cheap
Ultimately a lightweight wheel has heat treating in the manufacturing process, and comes out of the factory light and stiff. If you them significantly heat them again for powder coating you effect the previous process, and then you see these wheel failures.
We tend to suggest getting wheels painted is the way forwards, as this heating is not required.
Interestingly for these reasons on racing / track / drift cars when they get their new forged wheels it says in the manual from the manufacturer they need to be replaced every 2 years, they're a service item, which is why so many are sold from Japan, they are used for this period then replaced. They are then bought by people here, and a significant number of them have cracks that need welding.