What causes aluminum TIG welds to go grey?

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What causes aluminum TIG welds to go grey/dull and not bright and shiny?
Reply:Often it's overheating the weld, running too low  with the amps and moving too slow. While it seems counter intuitive, cranking the amps up and running faster will reduce the total heat input vs using a lower amp setting and going slower. Because alum is such a good heat conductor, when you go slow at lower amps, the piece sucks out a large portion of the heat heats the entire piece. By using more amps you get the puddle going faster and out run the ability of the material to draw off the heat, reducing total heat input..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:One thing I've noticed and I have no idea why is that when I use thoriated tungsten my aluminum welds look more "chromeish" or shinny.Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:Thoriated vs what?
Reply:2% lanthanted.Torchmate 2x2 CNC with Flashcut CNC controlsHypertherm Powermax45 Esab ET220i Razorweld 195 MigRazorweld 200ac/dc TigTormach 770, Tormach xstechRazorweld, Vipercut/Vipermig, SSC Foot Pedal Dealer
Reply:4043 will get grey faster in the weather than 6061.Are you talking about right after the part is welded, or after days/weeks/months have passed?
Reply:excessive electrode positive, too much or too little gas flow, not clean tungsten, traveling too slow,Welding/Fab Pics: www.UtahWeld.com