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Hi cmbb, No need for hydrogen gas. Hydrogen is a safe gas just like most gas but needs the respect demanded of all gas fuels. I braze and weld all my Al with Oxy/Acet as well as Cu, Pb, SS or Fe. Al welding requires special attention to the cleaness of the base metal as well as the filler rod. Although a flux (borax & alcohol paste works well) will help, base metal prep before and during welding is very important. I have even used electrodes for stick welding Al as a filler rod with the orginal flux left on the filler for Oxy/Acet Welding. Below is a repost of some of my thoughts: You can use oxy/act to gas weld AL. You can use AL stick rod with the flux left on or use a scrap piece of AL with a flux made from borax with alcohol added to make a paste and just dip the filler rod into the flux when needed. If you keep your filler rod with-in the gas flame zone then a flux is not needed. Be sure to remove all flux when done welding as AL will continue to oxidize if the flux is left on. There is a couple tricks to Gas or Tig welding Al. As your heating the base metal you will notice the weld puddle will start swrilling and that is the correct time to add filler rod and move backwards/forwards. I like moving away from my weld puddle as you can see how much filler rod needs to be added. A split second latter wrinkles appear with-in the weld puddle and if you don't quickly remove the heat or move forawrd then your weld puddle will end up on the floor. While welding AL you will notice a black oxide scale appear on the surface and the weld puddle becomes very difficult to control. Stop and remove this black oxide with a new SS wire brush or new grinding wheel. It's very important to use new wheels as if the wheels had beem used on Cu or Fe you can't get rid of the black oxides. Filler rods also need precleaned with emery paper to remove oxides exspecially while Tig welding. On Fe filler rod, clean filler rod too bear metal as well as clean base metal 1" on either side of the weld joint or it will cause prosisity in the weld. You can also use a chill bar clamped to the backside of your weld joint base meterial.
A chill bar is a thick piece of metal, usually 1/2" x 2" wide copper, used to draw the heat thru the base metal but hold the weld puddle from dropping thru and the weld puddle will not stick to the chill bar base metal. On welding AL you can use a piece of "clean" steel, no scalling, SS or CU. On welding Copper a SS chill bar works best. On welding carbon steel a CU, AL or SS chill bar will work. T_Bone
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