After soda blasting the aluminum I washed it to remove the residue. When it dried there was still baking soda coating it. I put it in the dishwasher for a heavy clean running the standard cycle with no soap. When it was finished the residue was gone but there were black streaks where the baking soda had washed out of the threaded holes. Upon researching “how to clean black streaks from aluminum” I found that truckers use “Purple Power” to clean their aluminum fuel tanks. I purchased this from my local Autozone store. They keep it behind the counter for commercial use even though it is listed on their web site. I purchased a gallon and gave it a try. It worked well, removing all of the streaking on the castings.