I agree that theres a coating there, I'm not sure its always galvanizing 
though. I suspect its similar though and reacts similarly. I've gotten in the 
habit of cleaning 1/4" around the sheet metal I'm using when I weld. I like 
leaving most of the stuff on, it doesn't burn off too bad other than right 
where I'm welding and it doesn't seem to rust.
My next step is to buy a bigger grinder. I'm going to get a 5" with the thinner 
grip. I don't know what its called other than its not the paddle grip my 4 1/2" 
Makita has, that one makes my hands tired quick.
      From: G Mann via Mercedes <>
 To: Mercedes Discussion List <> 
Cc: G Mann <> 
 Sent: Friday, June 5, 2015 6:42 PM
 Subject: Re: [MBZ] Slag hurts
PC boxes are most likely clad with galvanize material. Galvanizing requires
the base metal be coated with Zinc compounds which can and WILL contaminate
your weld, thus welds that look like bird droppings. The job of rod flux is
to carry away the contaminates in the weld puddle, but the flux core wire
from China doesn't have enough volume of flux to combat zinc contamination
of the weld puddle.. in fact.. if you were using gas, you would have to
crank up the flow rate to over come it.

The fact that you are having splatter and slag issues should have keyed me
to tell you the zinc boiling off is likely the cause. I overlooked that..
my apology.

Try a welding a piece of the same material you have dressed with a grinding
wheel to clean steel.. see if it doesn't give you a much better weld. I
will lay bets it does.

Go to your local steel supplier and pick up some end cut scraps for
practice, in MILD STEEL only.. then run a few passes.. look at the
difference.. you should see immediate good results.. even with crappy
Chinese flux wire from Harbor Fright.

A good part of welding is knowing the metalurgy of the metal you are
joining.. and how it affects the weld.


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