Like others have said I don't understand the mechanism your having for the powder showing up but I would try JB, it is cheap. JB and the similar products on the market will stick to clean aluminum and are rated (somewhere on the package) and designed for Tensile Strength which is not important in your application as I understand it. However, I think your issue is erosion by impacts normal to the surface which is not a strong suit for aluminum and maybe the steel in the JB epoxy might hold up much better to the erosion you are seeing.