What is the best abrasive to use?

The answer depends on how much pressure is being used and even then, the recommendations need to be considered only as a “general guideline”:

** Due to the inherent clogging involved when sanding most Aluminum, we recommend either using products with Grinding Aids or using a Grease Stick to lubricate the abrasive to help prevent loading.

Legend:
Ceramic Plus:	Ceramic Alumina with a grinding aid on a heavy Y-wt. polyester backing
Ceramic OC:	Ceramic Alumina Open Coat on a heavy duty backing
Zirc Plus:	Zirconia Alumina with a grind aid on a heavy Y-wt. polyester backing
Zirc:	Zirconia Alumina on a heavy Y-wt. polyester backing
Zirc PC:	Zirconia Alumina on a X-wt poly/cotton backing
AO Plus:	Aluminum Oxide with a grinding aid (available on Y-wt. or J-Flex backing)
AO:	Aluminum Oxide (available on Y, X or J-wt. backing)
SC:	Silicon Carbide on a heavy Y-wt. polyester backing