10 "Rules of the Road" for TIG Welding Aluminum

Rule #1 Only weld aluminum that is weldable.

No technique or cleaning method matters much if the aluminum is not weldable. There are a few high strength aluminum alloys that are not designed to be fusion welded. The main 2 alloys to avoid welding on are 2024 and 7075. 2024 might not crack right away but will fail prematurely in service...7075 will often crack immediately depending on application.

pro tip: if you are asked to weld an aluminum part that has zero welds on it but only rivets or mechanical fasteners, it is probably not a weldable aluminum.

RULE #2. Only weld aluminum that is clean enough (new aluminum is often clean enough. Dirty aluminum needs cleaning)

RULE #3. Use the right filler rod…3/32” 4043 or 5356 filler rod is a good start

Washington Alloys Aluminum Filler Metal Chart

TIG filler metals that are commonly stocked in North America, there are roughly 10–15 AWS classifications, but only 6–8 are commonly used.

AWS Classification	Common Name	Primary Use
ER1100	Commercially pure aluminum	1100, 3003, decorative work, electrical applications
ER4043	5% Silicon	The most common general-purpose filler for 6061, cast aluminum, and many 6xxx alloys
ER4047	12% Silicon ("718")	Cast aluminum, brazing, leak-tight welds, low shrinkage
ER5356	5% Magnesium	Marine, structural aluminum, anodized parts, 5xxx alloys
ER5183	High-strength Mg alloy	Marine, cryogenic vessels, pressure vessels, 5083/5086 also used by many bike builders on 7005 tubing
ER5556	High-strength Mg alloy	Higher tensile strength than 5356 for certain structural applications

Washington Alloy provides individual data sheets describing each alloy, including chemistry, recommended base metals, tensile strength, melting range, and anodizing color. (Washington Alloy)

Several additional AWS aluminum filler alloys exist, although many distributors only stock them on request:

ER1070
ER2319
ER4009
ER4145
ER4643
ER4943
ER5554
ER5654
ER5554A (specialty)
ER2319 (aerospace)
ER4047A (some manufacturers)

These are generally intended for specific applications such as:

aerospace
elevated-temperature service
pressure vessels
automotive
cryogenic service
heat-treated 2xxx alloys

Which filler rods do most TIG welders actually need?

For approximately 95% of aluminum TIG welding, you can accomplish nearly every job with just these four:

ER4043 – General-purpose, easiest to weld, ideal for 6061 and castings.
ER5356 – Stronger, excellent for marine work and parts that will be anodized.
ER4047 – Excellent for cast aluminum, minimizing cracking, and sealing porous castings.
ER4943 – A newer alloy that combines the easy welding characteristics of 4043 with higher as-welded strength, making it a strong choice for many 6xxx alloy applications.

The "Big Two"

ER4043
ER5356

These cover the vast majority of hobby, fabrication, and repair work.

The "Next Two"

ER4047 - less porosity on cast aluminum
ER4943 - stronger fillet welds combining fluidity of 4043 with strength of 5356 - still might turn grey after anodizing

RULE #4. Make sure your tig torch is plugged in to correct dinse plug in (usually the dinse labeled EN or - with the TIG torch icon but read the manual to be sure) . Dont skip this step or you might chase your tail

RULE #5. Use AC current with AC balance set for just enough cleaning action (usually about 1/8” of frosty etching outside the bead)

RULE #6. Set AC Frequency to 60-120 hz when learning. Experiment with higher frequency settings later.

RULE #7. Use the right cup. BIG cups don't work well on Aluminum. Use a #5 thru #8 cup. A #6 gas lens is a great all around cup and a #7 clear cup helps if see better.

RULE #8. Use the right argon flow...enough flow but not too much. 2-3 CFH per cup size usually works but test it on scrap to learn the best flow rate

RULE #9. A 3/32” 2% lanthanated, E3, or LayZr tapered tungsten all will be fine for learning and are all usually good up to around 200 amps. If you need to weld thinner than .063” a 1/16” tungsten will work better, thicker than 3/16”, a 1/8” will work better

RULE #10. When using a foot pedal, Set machine amps to around 1.5 X metal thickness… example: 0.100” = 100 thousandths X 1.5 = 150 amps. You won’t always need all those amps but aluminum often needs more heat at first…Use foot pedal if ( or torch amp control) to control amps while welding.

Bonus RULE #11. When ending a bead, taper amperage while you move the arc around as the puddle shrinks to avoid a crater crack. Some folks simply move arc to edge of puddle while amperage tapers and find that works.

10 Rules of the Road for TIG Welding Aluminum