Scaling on tungsten in cup?

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Was wondering if this effects the weld, and what causes it. To the best of my knowledge this will happen over time even without  running the tungsten into the puddle.  I still see soot at the tack welds sometimes and they just wipe away. IDK if this is the cause or not though. But it's just some scaling which is in the cup between the sharpened point and gas lens. Thanx for any help guys.
Reply:I've seen this happen when welding on galvanized metal that wasn't 100% clear of the coating.  That stuff migrates to the inside of the cup and onto the exposed tungsten.Zip.
Reply:In normal use a tungsten should remain unaffected (and like it looks new) up inside the cup.Maybe you have a one-piece aircooled torch hose and are overheating it?  The hot conductor melts the inside of the hose, releases contaminants into the shielding gas.  (such as PVC vapors).  PVC-vapor laden argon will scale a hot tungsten that's up inside the cup.  This will of course also give you really oxidized and contaminated welds when it happens.  To test for this, feel your torch cable while welding one of your thicker typical welds... should not get noticeably hot to the touch.Last edited by jakeru; 05-05-2012 at 12:46 PM.
Reply:How long is your post flow? and are you remaining in the same spot till it stops? Sometimes moving the torch to quickly leave the tungsten open with sheilding gas.
Reply:Thanx for the replys guys. It's a water cooled torch. I'd say not heat effected. 65 generally or less and I just see it on tacks. But I will check the next intercooler I do to see if that possible. I can see it. I have done some welding occasionally and forgot to turn the cooler on. Had one pop before. But it bust the line and was obvious as it leaked. Although the weld looks OK. Not thing really out of the ordinary...I do get a spot of porosity for no reason it seems at time. But I usually think it's a gust of wind I didn't feel or a some fluke. The weld will still look just fine, but I will get a hole at the end of the weld.Post flow is about 5-6 seconds. But if I weld something pretty hot I will bump the peddle to keep it going. Again, it's not the tip I'm having a problem with. It's natural color.