You have to be careful what acids you use in cartridge brass, particularly any which will be reloaded. Most acids at significant concentrations will dissolve the zinc and leave you with soft, porous copper. I think it was Ken Mollohan or maybe Felix Robbins who explained the chemical reasoning behind the use of CITRIC acid for safely cleaning cartridge brass. No other additives are necessary unless the brass has any wax or oil on it. A concentration of 1/2 teaspoon of pure citric acid powder per gallon of water works well. Add a tablespoon of Dawn dishwashing liquid to cut bullet lube or any wax/oil. McCormick spice company produces cittric acid powder for canning tomatoes, but Lemi-Shine is easier to find in grocery stores, I use a full teaspoon per gallon of LemiShine. Lemon juice works too but it requires more per gallon.
The citric acid solution will actually passivate the brass surface as well as get rid of the corrosion and it allows a thorough safety evaluation of the brass after cleaning because any zinc-depleted soft spots will show as bright copper.
I recently took a bunch of jacketed bullets which had been corroded with mouse urine and swished them in a jar of citric acid solution, they were shiny as a new penny in under five seconds. All my cartridge brass gets the SS pin tumble in a rotary tumbler filled with the 1 tsp Lemi-Shine/1 Tbs Dawn/gallon rainwater solution.
Citric acid will also remove rust from and passivate stainless steel. It is great for cleaning sinks and the SS 10/22 barrel that got left in a boat over the winter and helps keep corrosion from recurring.