Found the info below researching suitable fasteners with aluminum earlier today with the goal to avoid and/or minimize galvanic corrosion:

You probably know that, were it not for its toxicity, the ideal fastener material is cadmium plated steel. (Note: Military uses these fastener types.) It is so close to aluminum on the galvanic scale that there is no galvanic corrosion, it is corrosion resistant itself, and it has great lubricity. Nonetheless, cadmium is a cumulative poison, should be reserved for only the most critical applications, and even then is being rapidly phased out.

The next best material is aluminum plating or coating, again because the galvanic potential is zero. You can investigate Ivadizing for vapor deposition of aluminum, or AlumiPlate for electroplating of aluminum. I fear that you may find the cost unacceptable though.

I am a bit confused by your reference to stainless steel brackets because these will (theoretically) cause the aluminum to galvanically corrode regardless of the fastener material. And, presumably being larger in surface area than the hardware, they will have a more powerful impact.

All of the above not withstanding, you didn't mention how the aluminum is corrosion proofed, so the question is a bit open. But I have seen stainless fasteners used on architectually anodized aluminum in outdoor exposure without any substantial problems. The zinc plating is not a good idea in my opinion because it will be short lived.

Ted Mooney, P.E.
finishing.com
Brick, New Jersey