Originally Posted by cgocifer
In my previous professional life, I was a metal fabricator trained and certified in TIG (GTAW), MIG (GMAW), SMAW (stick), for all metals including dissimilar metals. I've heard a lot of people refer to the alternative for stainless steel as being aluminum. That is totally incorrect unless someone completely fabricates an entire system out of it, which would be ridiculous due to the less than optimal nature of aluminum to withstand vibration and temperature changes over long periods of time. You simply cannot weld aluminum and steel together without a special piece called a datacouple which is a double sided piece of steel and aluminum fused at the molecular level by very high explosives. Also, when steel and aluminum are in direct contact with eachother, a process called electolysis takes place and very quickly erodes the aluminum. So, what is it that people are talking about? It is aluminized steel. Basically, steel coated with an aluminized paint that helps to resist corrosion. It just sounds fancier by calling it aluminized. Stainless steel can however, be welded to regular, mild (carbon) steel as long as the correct alloy of stainless steel filler metal is used. I used to use 316 or 309 stainless steel filler alloy when joining SS to std. steel. Oh, as for aluminum being cheaper than steel, that is untrue. Aluminum is much more expensive than steel, especially 6061-T6, which is the structural grade of aluminum used in most structural applications. Mild steel, yes, even "aluminized" steel is much less expensive than stainless steel. If you can spring for it, I agree, go for the stainless, it will outlast steel and aluminized steel.
Sorry for the longwinded explanation, but I'm a bit of a tech. snob! :-)
Maybe It is not real aluminum just like various Chrome parts for our cars such as Chrome Grill and Chrome Windscreen offered by CTD-Germany are not real chrome... But the choice I had at the muffler store was between two materials one which was refered to as aluminum and one which was refered to as steel.. the aluminum one was significantly cheaper as it welded much quick to the existing pipes, but with consequences of unreliability.. that is as far as I know.. the person doing the welding suggested I use "aluminum as it will very likely last a few years untill I sell the car" I told him I have no plans of selling the vehicle.. he than suggested I invest a couple pennies in the "steel as it will outlast the vehicle"..
I have no extensive knowledge of either of these products, but it appears you do, but this information I wrote is that of my expereince at my time in the exhaust shop so take it for what it is worth... I don't know if what was refered to as Aluminum is acctually aluminized steel, or anything else, but I do know that it was much cheaper than the product refered to as "steel"