ER308L — What It Is and Why It Matters
ER308L is the standard filler metal for welding 304 and 304L stainless steel — the most common stainless alloy encountered in fabrication. The "L" designates low carbon content (under 0.03%), which minimizes carbide precipitation (sensitization) in the heat-affected zone and preserves the corrosion resistance of the welded joint.
ER308L is available as solid MIG wire and TIG filler rod. For MIG welding stainless, it is used with a tri-mix shielding gas (typically 90% helium, 7.5% argon, 2.5% CO2) or 98% argon / 2% CO2. For TIG, pure argon is standard with argon back-purge on the root side.
The companion products ER316L (for 316 stainless, adding molybdenum for enhanced corrosion resistance) and ER309L (for joining stainless to carbon steel) round out the three filler metals that cover the vast majority of stainless steel welding applications.
Frequently Asked Questions
Can I use ER308L on 316 stainless?
No — 316 stainless contains molybdenum for enhanced corrosion resistance, and the filler must match. Use ER316L on 316 base metal. Using ER308L on 316 produces a joint that lacks the molybdenum content needed for the intended corrosion resistance.
What does the L in ER308L mean?
L = Low carbon, meaning the carbon content is held below 0.03%. This low carbon content prevents the formation of chromium carbides in the heat-affected zone during welding, which would deplete chromium from the surrounding material and destroy its corrosion resistance — a condition called sensitization.