The Harris 316L Stainless TIG GTAW Welding Rod (part number 316LT50) is a low-carbon, molybdenum-bearing austenitic stainless steel filler metal classified ER316L per AWS A5.9/A5.9M. Available in 3/32 in (2.4 mm) diameter, 36-inch cut length, 10 lb box, this rod is specifically engineered for GTAW (TIG) welding of 316, 316L, and 317L stainless steel base metals — grades widely used in marine, pharmaceutical, chemical, and food processing applications that demand superior resistance to pitting and crevice corrosion. The addition of 2–3% molybdenum to the 18% Cr / 12% Ni austenitic matrix provides the elevated resistance to chloride-induced pitting that distinguishes 316L from standard 304 or 308 grades. The "L" (low-carbon) designation limits carbon to ≤0.03%, preventing sensitization and intergranular corrosion even in heat-affected zones subject to multiple thermal cycles. Harris Products Group, a Lincoln Electric company, produces this rod under rigorous lot chemistry control with certified C/C documentation traceable to melt heat numbers.
The 3/32 in diameter is the primary production size for medium-weight stainless applications: Schedule 40 pipe in the 1–4 in NPS range, structural 316L plate up to 1/2 in, pressure vessel fabrication, and heavy-duty commercial kitchen and dairy equipment. The larger diameter provides higher deposition rates than 1/16 in rod while maintaining the precise arc control characteristic of TIG welding.
| Attribute | Value |
|---|---|
| AWS Classification | ER316L (AWS A5.9/A5.9M) |
| Harris Part Number | 316LT50 |
| Diameter | 3/32 in (2.38 mm) |
| Cut Length | 36 in (914 mm) |
| Package Weight | 10 lb box |
| Carbon Content (max) | 0.03% (low-carbon "L" grade) |
| Chromium Content | 18.0–20.0% |
| Nickel Content | 11.0–14.0% |
| Molybdenum | 2.0–3.0% |
| Manganese | 1.0–2.5% |
| Silicon | 0.30–0.65% |
| Tensile Strength (as welded) | ≥75,000 psi (517 MPa) |
| Yield Strength (as welded) | ≥54,000 psi (372 MPa) |
| Elongation (as welded) | ≥35% |
| Polarity | DCEN (Direct Current Electrode Negative) |
| Shielding Gas | 100% Argon or Ar/He blends |
| Process | GTAW (TIG) |
| Base Metals | 316, 316L, 316H, 317, 317L stainless steels |
- Marine Fabrication: Boat hardware, propeller shafts, through-hulls, ladders, handrails, and deck fittings fabricated from 316L stainless require ER316L filler to maintain the molybdenum content in the weld metal that resists seawater pitting and crevice corrosion at fastener holes.
- Pharmaceutical & Biotech: Vessels, piping, and heat exchangers handling saline solutions, cleaning agents, or fermentation media where chloride-induced pitting must be avoided. 316L with ER316L filler is the minimum specification for most BPE (Bio-Processing Equipment) applications.
- Chemical Processing: Acetic acid, sulfuric acid (dilute), phosphoric acid, and chloride-containing process streams in chemical plants. The molybdenum addition provides broad-spectrum resistance to pitting from halide ions at temperatures up to 140°F (60°C).
- Food & Dairy: Cheese vats, brewery fermentation tanks, pasteurizer heat exchangers, and high-chloride CIP (clean-in-place) systems. 316L base metal with matching ER316L filler is often specified where 304 does not provide adequate corrosion life.
- Pressure Vessel Fabrication: ASME Section VIII 316L vessels handling aggressive media; ER316L is the SFA-5.9 classification filler required by most 316L vessel WPS documents.
- Pulp & Paper: Digester vessels, bleach plant piping, and sulfite liquor storage tanks — aggressive chloride and acid environments where 316L is the standard material of construction.
Welding with 3/32 in ER316L TIG rod follows the same general GTAW principles as ER308L with some considerations specific to the molybdenum-bearing alloy:
Interpass Temperature Control: Limit interpass temperature to 300–350°F (150–177°C) maximum. This is more critical for 316L than mild steel because: (1) high heat input increases distortion on austenitic stainless, and (2) excessive interpass temperatures can promote carbide precipitation even in L-grade material if thermal cycles are extreme. Use an infrared thermometer or temperature-indicating sticks between passes.
Amperage for 3/32 in Rod: Run at 120–200 amps DCEN depending on material thickness. For 3/16 in 316L plate, 130–155 A with a moderate travel speed (4–5 in/min) provides good penetration and bead profile. For 1/4–3/8 in plate or heavy pipe wall, 175–200 A with multiple passes — keep each pass narrow to limit heat input per pass.
Tungsten: Use 3/32 in or 1/8 in 2% ceriated or lanthanated tungsten, sharpened to a 30° included-angle point. For high-amperage heavy-section work, 1/8 in tungsten is recommended for arc stability above 175 A.
Back-Purging: For pipe root passes and vessel penetrations, back-purge the weld interior with 100% argon at 5–10 CFH. 316L root-side oxidation (sugaring) is more detrimental than on 304 in aggressive service because the oxidized zone is depleted of both chromium AND molybdenum.
| Material / Position | Amperage | Tungsten Size | Gas Flow | Notes |
|---|---|---|---|---|
| 3/16 in plate, flat | 130–155 A | 3/32 in ceriated | 20 CFH Ar | Single pass root, 1–2 fill |
| 1/4 in plate, flat | 160–185 A | 3/32–1/8 in ceriated | 20–22 CFH Ar | Multi-pass, cool between passes |
| Sch. 40 pipe, 2 in NPS | 110–140 A | 3/32 ceriated | 18–20 CFH Ar | Back-purge root, 5 CFH Ar |
| Heavy plate >3/8 in | 180–210 A | 1/8 ceriated | 22–25 CFH Ar | Preheat to 150°F, back-purge fill |
- Separate Stainless Storage Area: Store ER316L rods in a dedicated stainless consumables cabinet away from mild steel rods and carbon steel grinding dust. Iron contamination creates rust on 316L welds and compromises the corrosion resistance the alloy is selected for.
- Temperature & Humidity: 40–120°F storage temperature with relative humidity below 50%. Unlike hydrogen-sensitive low-hydrogen stick electrodes, stainless TIG rods are not moisture-sensitive in the same degree, but high-humidity environments can cause condensation on cold rod surfaces, leading to porosity at arc start.
- Lot Traceability: For ASME code work, retain the certificate of conformance from each 10 lb box. The C/C documents the heat chemistry, ferrite number (FN), and mechanical properties required for PQR/WPS documentation. Keep the box label until the lot is used.
- Ferrite Number: ER316L weld metal typically deposits at 5–10 FN (Ferrite Number) as measured by the Schaeffler diagram. Adequate ferrite content prevents hot cracking (solidification cracking) in fully austenitic weld metal. Verify FN on C/C for critical pressure-containing applications.
- Pre-Use Inspection: Check rods for kinks, surface gouges, or oxidation before use. Minor surface tarnish may be cleaned with a stainless wire brush dedicated to stainless work. Heavily pitted or corroded rods should be discarded — corrosion products will introduce contamination into the weld pool.
Any commercially available DC TIG machine is compatible with Harris ER316L 3/32 in rod. For production stainless fabrication, machines with pulse capability are strongly preferred:
- Lincoln Electric Square Wave TIG 200 (K5126-1): Suitable for lighter 316L applications up to 3/16 in. Pulse control helps manage heat input on thin-to-medium gauge 316L sheet and tube.
- Lincoln Electric Precision TIG 225 / 275: The 275 A capacity handles heavier-section 316L plate and thick-wall pipe with 3/32 in ER316L at high amperage without arc instability.
- Lincoln Electric Aspect 375 / Invertec TIG 300/300: High-duty-cycle machines for production 316L vessel and piping fabrication. Full programmable pulse provides precision heat input management for multi-pass heavy-section work.
| Base Metal | ER316L Compatibility | Notes |
|---|---|---|
| AISI 316 / 316L | ✅ Primary match | Composition match including molybdenum — standard selection |
| AISI 316H | ✅ Acceptable | Use ER316H or ER317 for high-temperature (above 800°F) service |
| AISI 317 / 317L | ✅ Acceptable | ER317L preferred for direct 317L match; ER316L acceptable for general service |
| AISI 304 / 304L | ✅ Acceptable (overalloyed) | ER316L on 304 base is acceptable and provides additional corrosion margin |
| AISI 316 to 304 dissimilar | ✅ Excellent | ER316L bridges both compositions; excellent for mixed-grade assemblies |
| 316L to carbon steel dissimilar | ❌ | Use ER309L for stainless-to-carbon dissimilar joints |
ER316L is the premium austenitic stainless TIG classification for corrosion-critical applications. The addition of 2.0–3.0% molybdenum (vs. 0% Mo in ER308L) provides a fundamentally different corrosion mechanism response that makes ER316L mandatory in specific industries.
Molybdenum in the ER316L deposit stabilizes the passive film against attack by chloride ions and other halides. The mechanism: Mo⁴⁺ ions in the passive layer act as "chloride sponges," adsorbing Cl⁻ before it can initiate pitting. This effect is quantified in PREN (Pitting Resistance Equivalent Number): PREN = %Cr + 3.3×%Mo + 16×%N. ER316L PREN ≈ 26 vs ER308L PREN ≈ 18 — approximately 44% better pitting resistance.
- Carbon: ≤0.03% (L-grade, sensitization resistance)
- Chromium: 18.0–20.0%
- Nickel: 11.0–14.0%
- Molybdenum: 2.0–3.0% (pitting/crevice corrosion resistance)
- Manganese: 1.0–2.5%
- Silicon: 0.30–0.65%
- Ferrite Number (as-welded): 4–12 FN
- Marine environments: Saltwater splash zones, boat hardware, marine exhaust, offshore platform handrails. Cl⁻ concentration in seawater (19,000 ppm) requires Mo-bearing stainless for pitting resistance.
- Pharmaceutical (USP Class VI / cGMP): Bioprocessing vessels, fermenters, product contact surfaces in drug manufacturing. FDA and ISPE guidelines specify 316L stainless for product-contact components.
- Chemical processing: Sulfuric acid dilute solutions, acetic acid, formic acid, and organic acid service above concentrations where 304/308L sensitizes. ER316L required per NACE/API recommendations.
- Coastal architectural stainless: Exterior cladding, handrails, and structural stainless in ocean-adjacent locations. Many marine architects specify 316L stainless as standard.
ER316L (low carbon, ≤0.03% C) is the standard for virtually all welding of 316L and 316 base metals where the weld will see: (a) sustained temperatures 800–1500°F in service, (b) post-weld exposure to corrosive media without full solution anneal, or (c) code requirements (ASME B31.3, FDA, etc.). ER316 (standard carbon, ≤0.08% C) is only preferred when maximum weld metal strength is required in high-temperature structural applications that will be fully annealed after welding. For 99% of fabrication and repair welding on 316/316L base metal, ER316L is the correct choice.
ER316L satisfies ASME Section IX P-No. 8 Group 1 filler metal requirements for austenitic stainless pressure piping and vessels. AWS D1.6 pre-qualifies ER316L for Group A (austenitic stainless) structural welding. It is the standard filler in API 582 and ASME B31.3 Table A-1 for 316/316L pressure piping construction.
Q1: What makes ER316L better than ER308L for marine applications?
The critical difference is molybdenum (Mo). ER316L contains 2–3% Mo, which raises the pitting resistance equivalent (PRE = %Cr + 3.3×%Mo + 16×%N) significantly versus ER308L which has no molybdenum. Chloride ions in seawater aggressively pit and crevice-corrode welds that lack sufficient molybdenum content. Marine hardware, boat fittings, and offshore structural components in 316L stainless should always be welded with matching ER316L — using ER308L in these applications produces weld zones with lower pitting resistance than the base metal.
Q2: Can I use ER316L on 304 stainless?
Yes, ER316L can be used on 304 or 304L base metal and is considered an over-alloyed approach. The additional molybdenum provides extra corrosion resistance margin, which is beneficial in borderline chloride environments. The cost premium of ER316L over ER308L is the main consideration; for standard 304 applications in non-chloride service, ER308L is more economical and equally adequate.
Q3: What is ferrite number (FN) and why does it matter for 316L welds?
Ferrite Number (FN) is a measure of the small amount of ferrite microstructure present in an otherwise fully austenitic weld deposit. FN 3–10 is typical for ER316L weld metal. Adequate ferrite prevents solidification hot cracking — a defect mode in fully austenitic welds where the last liquid in the weld pool solidifies under tensile stress. Harris ER316L is formulated to deposit in the correct FN range. The FN is documented on the certificate of conformance and is required for ASME pressure vessel code qualification.
Q4: What diameter ER316L TIG rod should I use for pipe welding?
For Schedule 10S–40S pipe in 1–2 in NPS (wall 0.083–0.154 in), 1/16 in diameter is preferred for root passes; 3/32 in for fill and cap passes. The 3/32 in rod (316LT50) is the standard choice for medium-wall pipe and heavy plate fill passes. For large-diameter heavy-wall pipe (4 in NPS and above), 3/32 in or even 1/8 in diameter may be used for cap passes at higher amperage.
Q5: Does ER316L require preheating before welding?
Generally, no. Austenitic stainless steels including 316L do not require preheat. In fact, preheating is generally discouraged because elevated interpass temperatures increase sensitization risk and distortion. However, if the base metal is extremely cold (below 40°F/4°C), allow it to reach shop temperature (above 50°F) before welding to prevent moisture condensation that causes porosity.
Q6: Is the Harris 316L rod certified to ASME standards?
Yes. Harris ER316L (316LT50) conforms to AWS A5.9/A5.9M, which is adopted as SFA-5.9 in the ASME Boiler and Pressure Vessel Code Section II, Part C. The filler is suitable for qualifying welding procedures under ASME Section IX and for production welding on ASME Section I, Section VIII, and B31.3 piping systems. Each 10 lb box includes a certificate of conformance traceable to a specific melt heat number.
Q7: What is the difference between ER316L and ER316LSi?
ER316LSi adds silicon (Si) at a higher level (0.65–1.0%) versus ER316L (0.30–0.65%). The higher silicon in LSi improves wetting and bead shape in MIG (GMAW) welding. For TIG welding, the performance difference between ER316L and ER316LSi is minimal — either is suitable for TIG applications. ER316L (without the Si suffix) is the standard TIG rod and is widely stocked; ER316LSi is more commonly specified for MIG wire applications where weld pool fluidity and bead appearance are important.