First off, I hope all this helps.
http://en.wikipedia.org/wiki/Galvanic_series
Let's first assume we are using passivated, 316 Stainless steel
Aluminum will corrode when placed in contact with Stainless steel + an electrolyte. Stainless is much more noble than aluminum.
Notice how much closer Zinc plating is to Aluminum, and in fact zinc plating is less noble (zinc will corrode) which will protect the aluminum.
You can give some protection to a stainless bolt / aluminum mechanical joint by means of sealing the threads from one another. Anaerobic thread sealants are popular.
http://www.henkelna.com/adhesives/a...dlockers-gaskets-sealants-retaining-14883.htm
Use a threadlocker in an engine case with aluminum threads, and you have asked for quite a bit of trouble that I doubt you'll want.
Use a thread sealant
http://www.henkelna.com/industrial/thread-sealant-thread-sealing-loctite-anaerobics-14405.htm
Thread Sealants
Loctite Thread Sealants are anaerobic adhesives that instantly provide a durable seal between close fitting threads to prevent the costly leakage of gas and liquids. Thread sealing is achieved as the anaerobic compound cures when confined in the absence of air, and between close metal fitting surfaces. When used to lock threaded assemblies together, anaerobic adhesives prevent loosening and corrosion of the fastener, maintain proper clamping force, and offer controlled torque for removal of the assembly.
Bonus round. Stainless steel is rather noble, doesn't like to react. Anaerobic thread sealants require what?
Thread sealing is achieved as the anaerobic compound cures when confined in the absence of air, and between close metal fitting surfaces.
Absence of air, presence of metal for thread sealants (also thread lockers). There may be metal there, but it's aluminum (trace amounts of corrosion-able copper alloy elements, maybe) and stainless steel (does not play well).
We need a primer, something to start off the chemical reaction in a thread assembly.
Primers for Anaerobic Products
These anaerobic primer products range from solvent-based surface activators to acetone and isopropanol based primers that offer a wide reaching range of applications. Many of Henkel's Loctite primers help speed the cure of our anaerobic adhesives and sealants.
http://www.henkelna.com/industrial/...m?keywords=anaerobic&primaryFacet=00000002A1#
My favorite is Loctite 7649 Primer N
http://www.henkelna.com/industrial/product-search-1554.htm?nodeid=8797888086017
Primer T works good, but doesn't have Primer N's 30 day part life
http://www.henkelna.com/industrial/product-search-1554.htm?nodeid=8797888413697
Me? I use good zinc plated or black oxide hardware with loctite wicking grade thread lockers. Correct torque values, great retention and easy breakaway torques. Stainless steel can be wicked to deal with.
http://www.henkelna.com/industrial/green-threadlockers-pre-assembled-wicking-13227.htm
TL,DR : And that's how I single-handed saved christmas. Go read everything, don't be lazy.