Sorry, the correct filler wire is 4043.
thanks,

It would help us to help you if we knew the following:

Are you following your WPS?

What is your cleaning process?

We use an aqueous degreaser followed by a clean stainless steel wire brushing to remove the oxide layer, then MEK or iso alcohol, then another round with the wire brush just prior to striking the arc.  Make sure all surfaces are smooth!  Also, wiping the filler down with MEK or alcohol or acetone might help some. 

What current are you using?

In my experience I have found AC to work the best.  Others like the smooth run of DCEN.

What gas are you using?

I have had better luck with argon than with anything else.  In my opinion, exotic mixes are a waste of my money. 

Are you back-gassing the weld?

If not, then you're setting yourself up for failure, especially if you're making class A welds to D17.1.  The backside will melt through and absorb contaminants and moisture from the surrounding air, causing porosity to form.

There is also the consideration of you, the welder, and your abilities.  Have you had experience welding aluminum before?  Have you welded tubing before?  If you're new to either one, it could take some time to learn.  Try running out your WPS on sheet, first to make sure your cleaning methods work well.  Cut each weld open to see where and how much porosity occurs.  If it's on the edges of the joint, then you're likely not cleaning enough or with the wrong materials.

Good luck, and let us know how it turns out.

We had lots of trouble passing D17.1 X-ray weldor quals on aluminum sheet.  The oxide always killed us.  It would float to the centerline of the weld (on the surface) and show up on the X-ray as a "linear" indication.  I sectioned every one through the "linear" and never ever saw a single crack using 40X.  In some cases, the only way we could pass the weldor qual was to use full DCRP and wreck the electrode point.  Of course, our production parts were not welded that way, but they were not x-ray'd either.  We went the whole route with stainless brushing, acetone, backing gas, wiping the filler wire, etc.  etc.. etc...I suppose if it was a procedure qual, and not a weldor qual, our hands would have been tied.  The only thing we can do on our production parts is play with the %DCRP on the square wave power supply.

Check out the post about argon purity posted two weeks ago. It solved our proplem with porosity.

We have just completed procedure qualifications on 3/16" sheet with GMAW.  .045" wire, DCEP, Argon, 2G and 3G up runs, no backing or purge, CJP to D1.2 spec.  Got the tensiles back yesterday (28ksi - 32ksi).  Acceptable porosity.  Not even a hint of a break in the bend straps.  And with the humidity here in South Tejas, too.  So no, I very much doubt humidity has much to with it in this case.