Aluminum TIG Rod Size Guide: Plate Thickness, Current, Cup and Argon Flow in One Table

The most common question we get about aluminum TIG rods is not which alloy — it is which diameter: “I am welding 3 mm plate, do I buy 2.4 or 3.2?” Too thin, and the rod melts away before the joint is filled, so you keep reaching for a new one. Too thick, and the rod pulls heat out of the puddle, the base metal does not fuse properly, and oxide gets folded into the weld. This guide from Mastership (sole authorized distributor of Canadian Indalco aluminum welding consumables in Asia) puts plate thickness, rod diameter, tungsten size, current, cup size and argon flow in one table, based on the TIG parameter tables that AWS A5.10 filler manufacturers publish.

The short answer: one rule

On thin plate, rod diameter roughly equals plate thickness; on thick plate, rod diameter is roughly half the plate thickness. 1.6 mm plate takes a 1.6 mm rod, 3.2 mm plate takes 2.4 mm, 6 mm plate takes 4.0 mm, and 10 mm and up takes 4.8 mm. When you are between sizes, pick the thinner one — a thin rod costs you a few extra rod changes, a thick one costs you fusion.

Plate thickness × rod diameter × current (aluminum TIG, AC, argon)

Plate thickness	Rod diameter	Tungsten	Current (A)	Cup	Argon flow
1.6 mm (1/16 in)	1.6 mm	1.6 mm	60–80	#6 (3/8 in)	9 L/min (20 cfh)
2.4 mm (3/32 in)	2.4 mm	2.4 mm	85–120	#6	9 L/min (20 cfh)
3.2 mm (1/8 in)	2.4 mm	2.4 mm	125–160	#6	9 L/min (20 cfh)
4.8 mm (3/16 in)	3.2 mm	3.2 mm	190–220	#7 (7/16 in)	12 L/min (25 cfh)
6.4 mm (1/4 in)	4.0 mm	4.0 mm	200–300	#8 (1/2 in)	14 L/min (30 cfh)
9.5 mm (3/8 in)	4.8 mm	4.8 mm	330–380	#10 (5/8 in)	17 L/min (35 cfh)
12.7 mm (1/2 in)	6.4 mm	6.4 mm	400–500	#10	19 L/min (40 cfh)

Typical reference values from the TIG procedure tables published by AWS A5.10 aluminum filler manufacturers (AC with high-frequency start, 100% argon, flat position). Actual parameters depend on joint design, preheat and equipment; your qualified WPS and PQR govern. Cup number is the inside diameter in sixteenths of an inch — #6 is 3/8 in.

What goes wrong with the wrong diameter

• Too thin: the rod melts the moment it touches the puddle, filler cannot keep up, the bead is concave and you change rods constantly. Welders then dwell longer to fill, and heat input goes up without meaning to.
• Too thick: the rod acts as a heat sink. Feeding it chills the puddle, the base metal does not fuse, and the oxide on the rod tip is more easily folded into the weld as an inclusion. Aluminum conducts heat several times faster than steel, so this bites harder than it does on steel.
• Tungsten follows the rod: the table pairs equal tungsten and rod diameters because the current range sets both. Raise the current and a thin tungsten balls up while a thin rod cannot fill.

Indalco TIG rod diameters

Indalco TIG rods come in 1.6, 2.0, 2.4, 3.2, 4.0 and 4.8 mm, packed in 10 kg boxes; the 6.4 mm rod listed for 12.7 mm plate is a special order — ask first. Diameters and packaging per grade are on the product pages: ER4043, ER4047, ER5356, ER5183, ER5554. For which grade matches which base alloy, see our aluminum filler selection guide.

How to read a TIG rod specification

A box of rods is normally specified as grade × diameter × length, for example ER5356 × 2.4 mm × 1000 mm. The grade sets the chemistry (and so the base metals it suits), the diameter sets how thick a plate it can fill, and the length is usually 1 metre (36 in / 914 mm in North American packaging). Cut-length rods for TIG are called TIG rods or filler rods; spooled wire for MIG is MIG wire.

Three details that get overlooked

• Keep the rod clean. Hydrogen is the main cause of porosity in aluminum welds, and moisture and oil on the rod surface are hydrogen sources. Put unused rods back in the box; do not leave them lying on the bench overnight.
• Keep the rod tip inside the gas shield. A hot rod tip oxidizes the instant it leaves the argon, and the next dip carries that oxide into the puddle. At the end of a weld, let the tip cool inside the shield.
• Aluminum TIG means AC. The oxide film on aluminum melts far above the metal itself; AC breaks it up through cathodic cleaning on the electrode-positive half cycle. DC electrode-negative will not remove it.

Frequently asked questions

1.6 or 2.4 mm rod for 3 mm aluminum plate?

2.4 mm. At 125 A and above, a 1.6 mm rod melts too fast to fill the joint. 2.4 mm is the standard size for 2.4–3.2 mm plate and the most versatile diameter to keep in stock.

Can I cut MIG wire into lengths and use it as TIG rod?

Same chemistry, so technically yes, but MIG wire is 0.9–1.6 mm and only suits the thinnest plate; it is soft and retains cast from the spool, which makes it awkward to feed. Use cut-length rods for TIG.

Is more argon always better?

No. Too much flow turns turbulent at the cup and pulls air into the shield, giving porosity and black smut. Stay within the 9–19 L/min range for the cup size, and use a windbreak outdoors rather than opening the valve.

Stock and samples

Mastership is the sole authorized distributor of Canadian Indalco aluminum welding consumables in Asia. ER4043, ER4047, ER5183, ER5356 and ER5554 TIG rods from 1.6 to 4.8 mm are in stock in Taiwan, shipped with the original datasheet and mill test certificate (MTC). Tell us your base alloy and plate thickness and we will recommend a diameter and send samples for trial.