Electrode comparison

ER309L vs ER316L

ER309L handles dilution on dissimilar joints; ER316L handles chlorides on matching 316 work. Different problems, different wires.

ER309L vs ER316L at a glance

	ER309L	ER316L
AWS specification	AWS A5.9/A5.9M	AWS A5.9/A5.9M
Process	TIG (GTAW) / MIG (GMAW)	TIG (GTAW) / MIG (GMAW)
Form	Solid wire / rod	Solid wire / rod
Tensile strength (min)	75 ksi	70 ksi
Yield strength (min)	45 ksi	40 ksi
Elongation (min)	30%	30%
Impact toughness	Not required by the specification	Not required; austenitic deposits remain tough at low temperature
Polarity	DCEP (GMAW), DCEN (GTAW)	DCEP (GMAW), DCEN (GTAW)
Positions	Flat, Horizontal, Vertical, Overhead	Flat, Horizontal, Vertical, Overhead
Penetration	Medium	Medium
Deposition rate	Medium to high depending on process	Medium to high depending on process
Coating / core	None — bare wire or rod	None — bare wire or rod
Slag	None; light oxide film to be cleaned	None; light oxide film to be cleaned or pickled
Shielding gas	100% argon for TIG; tri-mix or 98/2 for MIG	100% argon for TIG; tri-mix or 98/2 for MIG
Storage	Clean, dry, isolated from carbon steel contamination.	Clean, dry and isolated from iron contamination.
Primary use	Stainless-to-carbon-steel transition joints	Marine and offshore piping and structures

Which should you use?

ER309L exists to tolerate dilution: welding stainless to carbon steel, or laying the first layer of an overlay, where a matching filler would be diluted into a crack-sensitive composition. ER316L exists to resist chlorides on 316 base metal. When you are joining 316 to carbon steel, dilution is the immediate problem, so ER309L or ER309LMo is specified rather than ER316L. On a 316-to-316 joint, ER316L is correct and ER309L would simply be the wrong chemistry.

Choose ER309L when

Stainless to carbon steel joints
Overlay buffer layers
Repair welding on unknown steels

Choose ER316L when

Matching 316 or 316L base metal
Chloride and seawater exposure
Sanitary and chemical process piping

Amperage compared

Diameter	ER309L	ER316L
0.030 in (0.8 mm) MIG	50–150 A	50–150 A
0.035 in (0.9 mm) MIG	70–180 A	70–180 A
0.045 in (1.2 mm) MIG	100–250 A	100–250 A
1/16 in (1.6 mm) TIG	40–90 A	40–90 A
3/32 in (2.4 mm) TIG	70–130 A	70–130 A
1/8 in (3.2 mm) TIG	100–180 A	100–180 A

Ranges are typical starting points. Diameters listed for only one electrode are shown as — for the other.

ER309L vs ER316L — common questions

Which wire for 316 stainless to mild steel?

ER309L is the standard choice; ER309LMo is specified where molybdenum must be carried into the transition weld. Follow the governing WPS.

Does ER309L resist pitting like ER316L?

No. It has more chromium but no molybdenum, so it does not match ER316L in chloride environments.

Can ER316L be used for a dissimilar joint?

Not safely on stainless to carbon steel. Dilution drops its alloy content into a martensitic range and the weld is liable to crack.

Full specifications

ER309L

AWS A5.9/A5.9M

ER309L is the bare filler for welding stainless to carbon steel — over-alloyed at 23Cr-12Ni so the joint stays crack-free after dilution.

ER316L