TIG Welding Aluminum: Issues with Argon 4.8 Gas Quality?

Hello,
I have been welding aluminum from time to time for several months, I don't have much knowledge, which is why I would like to advise you on what may be causing my problem.
Is it possible that I got poor quality gas?
I add photos showing the welds located on the old and the new cylinder, the parameters were identical, the material was the same, I did not even sharpen the electrode, only changed the gas cylinders.
- the material was 3-4mm thick,
- I welded at around 120A,
-Hz I always have 150
- balance set to 35 (on a 10-90 scale),
- gas is Argon 4.8.

I will be grateful for all tips, advice etc.
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Is. I use 4.9 myself and sometimes have problems after changing the cylinder. It only reveals with alu. The distributor justifies this by the fact that a small amount of gas should be left in the cylinder, nobody does, and in large companies, cylinders land under the cloud, with valves open. When filling, no-one sucks the contents, only pumps by weight, so you can hit almost everything including water. There are companies that have cylinders with built-in reducers and then you have a guarantee of purity, but financially it comes out ...

many thanks for the answer, can you complain about such poor quality gas? does it not make sense?
the pictures also show poor cleaning around the joints is also a fault of the gas or balance set wrong?

Theoretically yes, but a lot depends on the will of the seller. Set the balance at 50%, frequency at max.

For Alu Argon 5.0 Large cylinders, at 5.0 it is more expensive but the cylinders are checked and vented. With lower ones there is no time to do this (once all the gas has been released from the cylinder oxygen gets into the cylinder, oxygen is the enemy of welding and welds unless they are specialised mixtures and filler materials, consequently this prevents further welding). Smaller cylinders and technically inferior cylinders below 5.0 are only topped up, nobody checks them to see if they have been aerated. It is not for nothing that on the regulator, which you tighten to the cylinder, there should be a red mark before the first or last one on the scale, which prevents the cylinder from being air-locked. This is also the answer to why accidents happen with another gas, acetylene, because the red dots on the regulator are for suckers or not to develop hoses which, if several coils accumulate, act as a detonating fuse, consequently causing the cylinder to explode.