What causes "sugaring" when TIG welding?

by Bob
(Tacome, Wa.)

I'm going to take a stainless TIG test, I took one a few years ago and busted test. All the I was told was I didn't pass because of sugaring. I thought the weld looked great, what did I miss?

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Bob,
You might have lost your purge on the root or second pass. Sugaring is oxidation of the back side of a stainless weld that is also called granulation because it looks like sugar granules.

under magnification, its easy to see why it is something to avoid. It is a weak area that will trap bacteria, corrode, or crack prematurely.

to avoid sugaring, make sure you maintain your argon purge until at least the second pass is done.