I am not sure you can say Stainless steel and Aluminum will not corrode if put together. How quickly two metals corrode when in contact depends on how far apart they are on the periodic table, and Aluminum is particularly at risk when with iron and especially copper. This is the problem with, for example, Discovery 1s and Range Rovers where aluminum skins are mounted on steel frames. they are supposed to have a mastic to separate them, but if carelessness in the building, and time allows water to bridge between them the aluminum will corrode quite quickly. If possible it is best to use non metallic washers to prevent contact when bolting aluminum with steel or stainless steel fixings. Corrosion is a complicated and interesting subject, but in essence if two metals are together and there is any damp, one of them will corrode.