An older yet very good article explaining what,why and how to minimize a phenomena known as "Weld Smut."
How to recognize, minimize weld smut
PRACTICAL WELDING TODAY® MARCH/APRIL 2003
April 10, 2003
By: Frank Armao
When I weld any aluminum alloy, I see a covering, light gray to black in color, over the weld. I see it when I gas tungsten arc weld (GTAW), but it's worse when I gas metal arc weld (GMAW). What is it? Does it affect the mechanical properties of the weld? How do I get rid of it?
http://www.thefabricator.com/article/aluminumwelding/how-to-recognize-minimize-weld-smutEnjoy the read!
Respectfully,
Henry