MIG Aluminum Porosity ???

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I'm having trouble with porosity. I'm doing a 3/16" deep groove weld in the flat position between 3/16" 6063 and 3/8" 6061 using a 350p and spoolmatic 30a, 4043 .035 wire, pulsing, 50 arc length and about 550 wire speed, pure argon at 30 cfm, prep with stainless brush. The surface looks fine when done welding but when I grind it flush, swiss cheese. Any help would be appreciated.Ian TannerKawasaki KX450 and many other fine tools
Reply:The surface finish of whatever material you are using could be laced with contaminates. Extruded is really bad from the extrusion process. Plate from the rolling process and  not much better. You really need to remove a good amount of the surface material that could be diluted into your weld, then do a deox or chemical etch to remove errant oxides. Brushing just can't dig in that deep. Tig is more forgiving, as the mig process is very hot and fast, not allowing the outgasing to boil out. Another cause could be miosture in the argon. Also if you are washing the parts in water, heat and dry out your parts as they can absorb water in the mill surface.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:hole or leak in argon line could pull in air also.
Reply:Originally Posted by indawoodshole or leak in argon line could pull in air also.
Reply:I don't use the exact same set up but the arc length seem way to high/ along with the wire speed. I'm using a miller Mpa350. For 3/16 we're somewhere around 35 /260ipm. Any pictures??welderbob