I wouldn't say that the cleaning process is the same for aluminum as it is for stainless, but certainly you should strive to make the same end result in either case. Aluminum is much more prone to contamination. With stainless there is really no need to do anything, but mechanically clean the the metal. (e.g. No chemical cleaners are required, but I also feel the same with aluminum.) Make sure that you clean ~1" or so on either side of the joint with a stainless wire wheel, flapper disc, or flapper wheel. Try to do that same on the backside of the joint. Eliminate any burrs or overly sharp edges. You shouldn't have much of a land on this where you are tig welding the joint, but a hair of a land would be good, imho.
If you are not using a purge gas when making a CJP weld on stainless you are not going to get a sound weld. It will pretty much ALWAYS sugar without the use of a purge gas, flux cored stainless steel GTAW (Tig) wire, or a product such as solar flux. You do not need to use a secondary shielding gas like you would with titanium, but you defiantly need something on the backside to displace the oxygen if it is a CJP weldment. If you are not going to use a purge gas on a CJP weld on stainless you should be putting the root pass in with a wire such as R316LT1-5 or similar. Just make sure you brush the slag off before going back to a cold solid wire for the rest of the passes.
What are you using for wire on the 304 and what are you using for tungsten?
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