ER316L Filler Wire

When you are welding the “Marine Grade” of stainless steel (AISI 316), you cannot just grab any rod off the shelf. You need a filler metal that matches the superior corrosion resistance of the base material.

Whether you are TIG welding a micro-brewery tank or MIG welding boat railings, ER316L is the industry standard for molybdenum-bearing stainless steels. In this guide, we break down the chemistry, the shielding gas requirements, and the critical “L-Grade” advantage that prevents your welds from rotting from the inside out.

Classification: ER316L (ISO 14343-1A: W 19 12 3 L)

Specification: AWS A 5.9

Form: Solid filler wire, 1 meter standard lengths for TIG wire, Spool form for MIG wire.

What is ER316L?

Let’s break down the AWS A5.9 classification code to understand exactly what you are buying.

• ER: Electrode or Rod. This means it can be used as a MIG wire (Electrode) or a TIG cut length (Rod).
• 316: The Alloy Group. This indicates an Austenitic Stainless Steel containing 18% Chromium, 12% Nickel, and 2-3% Molybdenum.
• L: Low Carbon. This is the most critical part. The carbon content is restricted to a maximum of 0.03%.

Why the “L” Matters: In standard stainless steel (like 316), high heat from welding can cause carbon to combine with chromium, forming “Chromium Carbides.” This depletes the chromium at the grain boundaries, leading to Intergranular Corrosion (also known as “Weld Decay”). The “L” grade prevents this sensitization, keeping your weld corrosion-resistant.

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ER316L Chemical Composition and Mechanical Properties

Chemical Composition & The “Moly” Factor

The magic ingredient in ER316L is Molybdenum (Mo).

• ER308L (Standard): Contains Cr + Ni. Great for general corrosion.
• ER316L (Premium): Contains Cr + Ni + 2.0–3.0% Mo.

Molybdenum drastically increases the alloy’s resistance to Pitting Corrosion caused by chlorides (saltwater) and sulfuric acids. This is why 316L is mandatory for marine environments, chemical processing plants, and pharmaceutical equipment.

Shielding Gas Selection

Choosing the wrong gas is the #1 reason stainless welds turn grey, sugary, or rusty.

1. For TIG Welding (GTAW)

• Primary Choice: 100% Argon.
• Why: Provides a stable arc and protects the puddle from atmospheric contamination.
• Purging: For pipe welding, you MUST purge the inside of the root with 100% Argon. If you don’t, the backside will “sugar” (oxidize), creating a porous, brittle weld that will fail immediately.

2. For MIG Welding (GMAW)

• Short Circuit (Thin Metal): Tri-Mix (90% Helium / 7.5% Argon / 2.5% CO2). Helium provides the heat; CO2 stabilizes the arc.
• Spray Transfer (Thick Metal): 98% Argon / 2% Oxygen or 98% Argon / 2% CO2.
• Avoid: Do NOT use “C25” (75% Argon / 25% CO2) or 100% CO2. The carbon from the CO2 will absorb into the weld pool, turning your “L-grade” low-carbon weld into a high-carbon failure point.

ER316L vs. ER308L: Can I mix them?

This is the most common question in stainless welding.

Scenario 1: Welding 316 to 316

• Use: ER316L.
• Reason: You must match the Molybdenum content of the base metal.

Scenario 2: Welding 304 to 304

• Use: ER308L.
• Can I use 316L? Yes. You can use ER316L to weld 304 steel. It is actually an “overmatch” in quality. However, it is more expensive, so it is rarely done in production.

Scenario 3: Welding 304 to 316

• Use: ER316L.
• Reason: When joining dissimilar stainless grades, always filler match the higher alloy. If you use ER308L (no Moly) on a 316 part, the weld bead will be the “weak link” and will corrode first.

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⚙️ Welding Parameters (TIG)

Here are starting parameters for TIG welding with ER316L on DCEN (Direct Current Electrode Negative).

Metal Thickness	Filler Diameter	Amperage (DCEN)	Tungsten Size
1/16″ (1.6mm)	1/16″ (1.6mm)	45 – 75 A	1/16″ (2% Lanthanated)
1/8″ (3.2mm)	3/32″ (2.4mm)	85 – 120 A	3/32″ (2% Lanthanated)
3/16″ (4.8mm)	1/8″ (3.2mm)	130 – 175 A	3/32″ or 1/8″

ER316L Applications

ER316L is 19 Cr, 12.5 Ni, and 2.5 Mo alloyed solid filler wire rod as per AWS A5.9 specification.

The F Number of ER316L is F Number 6.

ER316L is used for welding of similar metallurgy materials such as AISI 316L, 1.4401 X5CrNiMo17-12-2, 316Ti and 316Nb alloys.

Welding Shielding gas for ER316L Wire

ER316L shall be used only with Inert Gas such as Argon and Helium for TIG welding.

ER316L when used for MIG welding, Argon with little addition of Oxygen is used to increase weld pool fluidity. 316L weld pool is inherent to be sluggish and oxygen addition increase its fluidity.

ER316L meaning

ER316L is a solid TIG-MIG filler wire rod used for welding AISI 316L stainless steel. Notable 316 metallurgy grades are TP316L, 1.4401 X5CrNiMo17-12-2, F316L, and SUS 316L.

• ‘ER’ means Electrode
• ‘316’ means the material type
• ‘L’ means Low Carbon

Chemical composition and mechanical properties of ER316L is stated in table above as required by AWS A5.9 specification for stainless steel welding electrodes.

ER316L Filler wire specification is AWS A5.9. ISO equivalent specification for ER316L is ISO 14343-1A. ISO equivalent filler wire for ER316L is W 19 12 3 L.

ER316L Test Certificate (MTC)

Click here to download ER316L MTC (material test certificate). This is an actual test certificate of Er316L filler wire rod.

Common Problems & Troubleshooting

1. “Sugaring” on the Backside

• Cause: Oxygen reaching the back of the hot weld.
• Fix: Use a back-purge system (Argon) or Solar Flux (a powder that melts to form glass shielding) on the root side.

2. Grey/Black Welds

• Cause: Too much heat or moving too slow. Stainless steel conducts heat poorly, so heat builds up quickly.
• Fix: Increase travel speed, use chill bars (aluminum or copper backing), or lower amperage.

3. Distortion (Warping)

• Cause: High coefficient of thermal expansion (stainless expands 50% more than mild steel).
• Fix: Tack weld every inch. Use “skip welding” or back-stepping techniques to distribute heat.

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