The best practice is to use aluminum fasteners and fittings. If this is done, there is no practical potential for galvanic corrosion. Again, for the reason stated earlier, you should not paint aluminum.
If you took the necessary parts made of aluminum, the next best option is stainless steel. In most environments, stainless steel fasteners and fittings can be directly bonded to aluminum alloys without any galvanic corrosion problems. Aluminum transport boxes can be used for various things depending on their size.
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Because stainless steel forms a passive oxide coating that helps insulate the two materials from each other. The only time that aluminum-stainless combination is a problem is in very acidic soils.
Under these conditions, acid clays can remove the inert oxide coating from stainless steel. If this happens, aluminum will grow preferentially and rapidly.
The least desirable material combination is to use aluminum with carbon steel screws and fittings. Unless the two materials are electrically isolated, the aluminum will corrode preferentially.
If you must use carbon steel bolts and fittings, the bolts, washers, nuts, and other parts should be coated to insulate them, and fittings should have a thin plastic or rubber sheet inserted between them and the aluminum.
In any case, do not paint carbon steel or aluminum. If available, galvanized bolts and fittings should be used instead of plain carbon steel as the zinc coating will corrode before aluminum.