This Video is about Tig welding a 2g aluminum Butt joint and how cleanliness of the metal affects the outcome.
Preparation of base metal is important but it all really depends on the situation.
For example, an outside corner joint on polished aluminum tread plate might only need a quick wipe down with acetone ...or it may not require any cleaning at all in order to get the desired result.
Lap joints and Tee joint fillet welds generally dont require much prep either as long as the metal is fairly clean and free from heavy oxidation.
But when full penetration is required as with an 11ga horizontal butt joint...
cleaning can make a lot of difference in the end result.
In this video, you can see that even when full penetration is achieved, its not very smooth until the last example where I cleaned the metal very thoroughly and even filed the edge to remove every last layer of oxide film.
The video above really shows the difference thorough cleaning makes.
One weld was not cleaned, the other weld was cleaned very thoroughly and the edge was filed with a clean file until it was shiny and smooth.
There was not much difference in the appearance but when the back side was blended off using a scotch brite disc, you can see a lot of linear porosity.
Most aluminum welds contain some level of porosity and sometimes its not a huge deal, but for a welding test, or for tig welding a critical part, linear porosity is usually not acceptable.
I dont want to over emphasize the need for cleaning aluminum because I realize that every situation calls for a different level of cleanliness.
But I have never welded any aluminum where I thought I cleaned it too much.
There is a relatively new filler metal called 4943.
It is very similar to 4043 filler metal but the properties are somewhat better and it also will respond to an aging heat treatment.
I got a sample at my local welding supply and Have been using it in place of 4043 for a while now..and I like it.