TIG welding gives you precise control over the filler metal you feed into the weld pool. Unlike processes that use a fixed-composition wire, TIG lets you choose a filler that matches or complements the base metal for specific strength, corrosion resistance, crack resistance, and service-temperature requirements. The wrong filler choice can cause porosity, hot cracking, under-matching strength, galvanic corrosion, or premature service failure.
This guide covers TIG filler selection logic across carbon steel (ER70S-2, ER70S-6, ER80S-D2), stainless See our TIG welding stainless steel article for more on this topic. steel (ER308, ER309, ER316, ER347), aluminum (ER4043, ER5356, ER4047, ER5556), nickel alloys (ERNiCr-3, ERNiCu-7), copper alloys (ERCu, ERCuSi-A, ERCuNi), and dissimilar metal combinations. Each filler recommendation depends on the specific base metal, joint design, service conditions, and applicable code or WPS.
This is a selection logic guide — not a buying guide, not a pricing comparison, and not a substitute for manufacturer data sheets, qualified welding procedure specifications (WPS), or applicable code requirements. AWS A5.xx classification standards and manufacturer technical data are the final authorities for filler metal selection.
AWS Classification System for TIG Filler Metals
Before diving into specific fillers, it helps to understand how AWS classifies TIG filler wire. Every TIG filler carries an “ER” prefix. The “E” stands for Electrode (the filler can carry current in processes where it does), and the “R” stands for Rod (the filler is fed cold into the puddle in TIG). All TIG filler wires use the ER prefix.
The numbering that follows tells you the alloy family and properties:
- ER70S-x: Carbon steel. “70” means 70 ksi minimum tensile strength. “S” means solid wire. The suffix (2, 3, 6) indicates deoxidizer level.
- ER3xx: Stainless steel. The three-digit number follows AISI grade numbering (308, 309, 316, 347, etc.).
- ER4xxx: Aluminum. The four-digit number follows aluminum alloy numbering (4043, 5356, 4047, 5556, etc.).
- ERNiCr-x: Nickel alloys. The designation includes major alloying elements (ERNiCr-3, ERNiCrMo-3, ERNiCu-7, etc.).
Suffixes carry important meaning. “L” means low carbon (max 0.03% C), needed for corrosion resistance in the as-welded condition. “H” means high carbon, specified for high-temperature creep service. “D” in ER80S-D2 indicates a modified deoxidizer level.
AWS Classification Quick Reference ER = Electrode or Rod (usable as both) 70 = 70 ksi minimum tensile strength S = Solid wire -6 = Deoxidizer level (higher number = more deoxidation) L = Low carbon (max 0.03% C) H = High carbon (0.04-0.08% C) D = Modified deoxidizer level (ER80S-D2)
The AWS classification guarantees minimum chemical composition ranges. However, individual manufacturer products may vary within the classification. Always consult the manufacturer data sheet for the actual composition and properties of the specific product you are using. The classification is a starting point, not the final word.
Stainless Steel TIG Fillers: ER308 vs ER309 vs ER316 and More
Stainless filler selection causes more confusion than any other category outside aluminum. Many welders assume any 300-series filler works for any stainless job. It does not.
ER308 / ER308L / ER308H
ER308 (19.5-22.0% Cr, 9.0-11.0% Ni) is the matching filler for 304 and 304L stainless steel. It provides matching corrosion resistance to the base metal and typically produces 4-12 Ferrite Number (FN) in the as-welded condition, sufficient to prevent hot cracking in most applications.
ER308L (low carbon, max 0.03% C) is specified for 304L base metal or whenever intergranular corrosion resistance is required in the as-welded condition. It is the preferred choice for corrosive environments including food processing, chemical, and pharmaceutical applications.
ER308H (high carbon, 0.04-0.08% C) is used for high-temperature creep service such as boiler tubes and superheater components. Do not use ER308H for corrosion service — the higher carbon content increases sensitization risk.
ER316 / ER316L
ER316 (2.0-3.0% Mo) is the matching filler for 316 and 316L stainless steel. The molybdenum addition provides enhanced pitting corrosion resistance in chloride environments. ER316L (max 0.03% C) is the default choice for any corrosion-critical 316 application — marine, chemical processing, food equipment, and pharmaceutical.
Critical: Using ER308 on 316 base metal produces a weld deposit with insufficient molybdenum content for the pitting resistance that 316 is selected for. In non-corrosive service it may be acceptable, but for any application where corrosion resistance matters — including food processing, chemical, or marine — use ER316/ER316L.
ER309 / ER309L
ER309 (23.0-25.0% Cr, 12.0-14.0% Ni) is specifically designed for dissimilar metal welding (stainless to carbon steel) and for cladding and buffer layers. The higher nickel content accommodates dilution from the carbon steel side and prevents martensite formation in the weld deposit.
ER309 is not a general stainless welding filler. Using ER309 as a general stainless filler instead of ER308 or ER316 produces a weld with different corrosion resistance and ferrite content than desired. If you need a matching filler for 304 or 316, use ER308L or ER316L respectively.
ER347
ER347 is columbium (niobium)-stabilized. It is used for stabilized stainless grades (321, 347) and for applications requiring resistance to intergranular corrosion after sensitization heat treatments or high-temperature service. It is more expensive than ER308L or ER316L and should be used only where stabilization is required.
Ferrite Number Relevance
Ferrite content matters for hot cracking prevention. The standard target range for general corrosion service is 4-12 FN. Higher ferrite (15-25 FN) may be specified for restrained joints or when welding thick sections. Lower ferrite or fully austenitic fillers may be required for cryogenic service or certain corrosive environments where ferrite preferentially corrodes.
Stainless Steel TIG Filler Comparison
| Filler | Cr/Ni/Mo Content | Ferrite Number Range | Matching Base Metals | Corrosion Resistance | Primary Use Case |
|---|---|---|---|---|---|
| ER308L | 19.5-22% Cr, 9-11% Ni | 4-12 FN | 304, 304L | General oxidizing environments, food, chemical | General stainless fabrication |
| ER308H | 19.5-22% Cr, 9-11% Ni (0.04-0.08% C) | 4-12 FN | 304H, 321H | High-temperature creep, not for corrosion | Boilers, superheaters |
| ER316L | 18-20% Cr, 11-14% Ni, 2-3% Mo | 4-12 FN | 316, 316L | Enhanced pitting resistance, chlorides, marine | Chemical processing, marine, food |
| ER309L | 23-25% Cr, 12-14% Ni | 15-25 FN | Dissimilar joints, cladding | Different from 308/316 — verify for corrosion service | Stainless-to-carbon steel, buffer layers |
| ER347 | 19-22% Cr, 9-11% Ni + Nb (10xC min) | 4-12 FN | 321, 347 | Stabilized against sensitization | High-temperature service, post-weld heat treatment |
Common Mistakes with Stainless Fillers
Using ER308 for 316 in corrosive service is the most common error — the weld deposit will lack molybdenum. Using ER309 as a universal stainless filler produces a weld with different corrosion properties than expected. Ignoring ferrite number requirements for critical service can lead to hot cracking or preferential corrosion. Assuming all “L” grades are interchangeable across 308, 309, and 316 is incorrect — each has distinct composition and applications.
Nickel-Alloy TIG Fillers: ERNiCr-3, ERNiCrMo-3, ERNiCu-7, and More
Nickel-alloy TIG fillers are a specialty area where mistakes are expensive. These fillers are not substitutes for stainless fillers — they have different corrosion resistance, mechanical properties, and cost profiles.
ERNiCr-3 (Inconel 82 / NiCr20Mn3Nb)
ERNiCr-3 is the most versatile nickel-alloy TIG filler. It is used for welding Inconel 600 and 601 base metals, for joining nickel alloys to stainless steel or carbon steel, and for overlays. It has good crack resistance, excellent high-temperature strength, and contains niobium for carbide stabilization.
However, ERNiCr-3 does not match the corrosion resistance of Inconel 625 or Monel base metals. For those, you need a matching filler.
ERNiCrMo-3 (Inconel 625 / NiCr22Mo9Nb)
ERNiCrMo-3 has higher molybdenum content for enhanced pitting and crevice corrosion resistance. It is used for Inconel 625 base metal, for cladding, and for aggressive chemical and marine environments where maximum corrosion resistance is required. It is more expensive than ERNiCr-3.
ERNiCu-7 (Monel 60 / NiCu30Mn3Ti)
ERNiCu-7 is used for welding Monel 400 and 404 base metals and for joining Monel to steel or stainless steel. It offers good corrosion resistance in marine, chemical, and hydrofluoric acid environments.
ERNi-1 (Nickel 61 / Ni >93%)
ERNi-1 is used for welding commercially pure nickel (Nickel 200/201). Its TIG use is limited outside chemical processing equipment.
ERNiCrMo-4 (Hastelloy C-276 / NiCr16Mo16W4)
ERNiCrMo-4 is designed for extreme corrosive environments including hydrochloric acid, wet chlorine, and ferric chloride. It is expensive and specified only where the service environment requires it.
Nickel-Alloy TIG Filler Comparison
| Filler | Matching Base Metals | Corrosion Resistance | Primary Applications | Cost Indicator |
|---|---|---|---|---|
| ERNiCr-3 | Inconel 600/601, dissimilar joints | Good general, high-temperature | Most versatile nickel filler, overlays | Moderate |
| ERNiCrMo-3 | Inconel 625 | Excellent pitting/crevice resistance | Chemical processing, offshore, chlorides | High |
| ERNiCu-7 | Monel 400/404 | Marine, HF acid, chemical | Monel welding, copper-nickel systems | High |
| ERNi-1 | Nickel 200/201 | General corrosion resistant | Chemical processing equipment | Moderate |
| ERNiCrMo-4 | Hastelloy C-276 | Extreme (HCl, wet chlorine, ferric chloride) | Severe chemical environments | Highest |
Critical Cautions for Nickel-Alloy Fillers
Nickel-alloy fillers require stringent cleanliness. Sulfur, lead, and phosphorus contaminants cause embrittlement in the weld deposit. Base metal preparation must be thorough.
Heat input control is critical. Nickel-alloy fillers require narrower parameter windows than carbon steel fillers. Excessive heat input can cause hot cracking.
Nickel-alloy fillers are not interchangeable with stainless fillers for stainless base metal. Use nickel-alloy fillers only where the application requires nickel-alloy corrosion resistance or high-temperature properties.
Preheat and interpass temperature requirements depend on the base metal specification, joint thickness, and service conditions. Consult the WPS or manufacturer recommendation.
Dissimilar Metal Filler Selection
Dissimilar metal joints require engineered filler selection. Dilution, thermal expansion mismatch, galvanic corrosion risk, and metallurgical incompatibility all come into play.
The Dilution Principle
When you weld dissimilar base metals, both base metals melt into the weld pool. The resulting weld metal composition is a mixture of the filler and both base materials. The filler must be selected so that the diluted weld metal has acceptable properties. This is especially critical for stainless and nickel-alloy joints.
Stainless to Carbon Steel
ER309/ER309L is the standard recommendation for joining stainless steel to carbon steel or low-alloy steel. Its higher nickel content (12-14%) accommodates dilution from the carbon steel side and prevents martensite formation in the weld deposit. However, joint geometry, plate thickness, and service environment may require adjustment. Consult a welding engineer for critical structural or corrosion-service applications.
Nickel Alloy to Stainless or Carbon Steel
ERNiCr-3 (Inconel 82) is the standard filler for joining nickel alloys to stainless or carbon steel. It offers excellent ductility and accommodates dilution across a wide range of dilution levels.
Copper to Steel
ERCuNi or ERCuSi-A are used depending on service requirements — ERCuNi for marine and corrosive environments, ERCuSi-A for decorative and light-duty brazing.
Aluminum to Other Metals
Aluminum-to-steel or aluminum-to-copper joints are generally not weldable with TIG fusion welding. These combinations are brazing territory. However, dissimilar aluminum alloys (such as 6061 to 5052) are weldable with the appropriate filler — use the filler that matches the more corrosion-resistant or higher-strength base alloy.
Galvanic Corrosion Consideration
When joining dissimilar base metals, the filler metal’s electrochemical compatibility with both base metals must be considered. Some combinations create a galvanic cell that accelerates corrosion in service, particularly in wet or marine environments.
Dissimilar Metal Filler Selection
| Joint Type | Recommended Filler | Key Concern |
|---|---|---|
| Stainless to carbon steel | ER309/ER309L | Dilution from carbon steel side; martensite formation if nickel content is too low |
| Nickel alloy to stainless | ERNiCr-3 | Thermal expansion mismatch; dilution accommodation |
| Nickel alloy to carbon steel | ERNiCr-3 | Dilution control; carbon migration risk |
| Copper to steel | ERCuNi (marine/corrosion), ERCuSi-A (light duty) | Galvanic corrosion; joint strength (ERCuSi-A is brazing) |
| Aluminum 6061 to 5052 | ER5356 or ER4043 | Filler selection based on service environment and temperature |
Common Mistakes with Dissimilar Metal Fillers
Using standard matching filler for dissimilar joints — such as ER308 for stainless-to-carbon steel instead of ER309 — produces a weld that may crack due to martensite formation. Assuming any “universal” filler works for all dissimilar pairs ignores the specific metallurgical requirements of each combination. Ignoring thermal expansion mismatch effects on joint design can lead to residual stress cracking. Not considering galvanic corrosion in wet service environments can lead to premature failure of the weld or adjacent base metal.
Cracking, Corrosion, and Compatibility Cautions
These risks exist in specific conditions, not universally. Proper filler selection, base metal preparation, and welding parameters prevent most of these issues.
Hot Cracking (Solidification Cracking)
Stainless fillers require ferrite number monitoring. The standard target range is 4-12 FN for most applications. Higher ferrite may be needed for heavily restrained joints. Lower ferrite or fully austenitic fillers may be required for cryogenic or certain corrosive services.
For aluminum, silicon content in the filler matters. ER4043 and ER4047 offer better crack resistance on 6000-series aluminum than ER5356 because silicon helps prevent solidification cracking.
For carbon steel, sulfur and phosphorus in the base metal can contribute to hot cracking when using ER70S-6. Proper base metal specification verification helps avoid this.
Nickel-alloy fillers require tight heat input control and proper crater filling technique to avoid solidification cracking.
Stress Corrosion Cracking
CRITICAL: Never use ER5356 on 6061 or 6063 aluminum for applications where the weldment will be exposed to sustained temperatures above approximately 150 degrees F (65 degrees C). This combination is known to cause stress corrosion cracking — a well-documented failure mode in aluminum TIG welding.
For aluminum in high-temperature service, use ER5554 on 5000-series base metals or ER4043/ER4047 on 6000-series base metals instead of ER5356.
Intergranular Corrosion
For stainless steels, low-carbon filler (L-grade, max 0.03% C) is required for as-welded service in corrosive environments. High-carbon fillers (ER308H) should not be used where corrosion resistance is needed. Note that filler selection does not prevent HAZ sensitization in the base metal — it ensures the weld metal itself is not the weak point.
Pitting Corrosion
Molybdenum-bearing fillers (ER316/ER316L, ERNiCrMo-3) are required for chloride environments. Using ER308 on 316 base metal produces a weld deposit with insufficient molybdenum for pitting resistance.
Galvanic Corrosion
Dissimilar metal joints create galvanic couples. The filler metal’s electrochemical potential relative to both base metals affects corrosion behavior. This is especially relevant for stainless-to-carbon steel joints in wet environments.
Porosity
Aluminum filler selection affects porosity susceptibility. ER5356 is more prone to porosity than ER4043, typically due to gas coverage or AC balance settings rather than filler quality. Stainless fillers with insufficient deoxidation can also produce porosity. Carbon steel fillers on contaminated base metal will suffer from porosity regardless of deoxidizer level.
For detailed defect troubleshooting, see our Common TIG Welding Defects guide.
Quick-Reference Selection Tables (Starting Recommendations Only)
The following tables provide starting-point recommendations for common base metal and filler combinations. Always verify with the filler manufacturer data sheet and applicable welding code before production.
Table 1: Carbon Steel
| Base Metal | Recommended Filler(s) | Key Considerations |
|---|---|---|
| Clean killed mild steel (A36, A516) | ER70S-6 | Best fluidity, bead appearance, and impact properties |
| Semi-killed or rimmed steel | ER70S-2 | Supplemental deoxidizers prevent porosity |
| Unknown steel composition | ER70S-2 | Safer choice when base metal chemistry is uncertain |
| Chrome-moly (A335 P11/P22) | ER80S-D2 | Preheat, interpass, and PWHT per base metal specification |
Table 2: Stainless Steel
| Base Metal | Matching Filler | Alternative Filler | Key Considerations |
|---|---|---|---|
| 304 / 304L | ER308L | ER308 (non-corrosion service) | Use ER308L for as-welded corrosion resistance |
| 316 / 316L | ER316L | ER316 (non-corrosion service) | ER308 insufficient Mo for pitting resistance |
| 321 / 347 | ER347 | ER308L (non-stabilized service) | Use ER347 where stabilization is needed |
| Dissimilar (SS to CS) | ER309L | ERNiCr-3 | Higher Ni content for dilution accommodation |
Table 3: Aluminum
| Base Alloy | Recommended Filler(s) | Alternative Filler | Key Limitations |
|---|---|---|---|
| 1100 | ER4043, ER4047 | ER5356 | ER4043 preferred for fluidity |
| 3003 | ER4043, ER4047 | ER5356 | General fabrication |
| 5052 | ER5356 | ER4043 | ER4043 reduces marine corrosion resistance |
| 5083 / 5086 | ER5356, ER5556, ER5183 | ER4043 | Use high-strength fillers for structural |
| 6061 / 6063 | ER4043 | ER5356 | ER5356 only if no sustained high-temperature exposure (above ~150 degrees F) |
| 356/357 castings | ER4043, ER4047 | ER5356 | ER4047 for thin sections and gap filling |
Table 4: Nickel Alloys
| Base Metal | Matching Filler | Primary Applications |
|---|---|---|
| Inconel 600/601 | ERNiCr-3 | General fabrication, dissimilar joints, overlays |
| Inconel 625 | ERNiCrMo-3 | Chemical processing, offshore, chloride environments |
| Monel 400/404 | ERNiCu-7 | Marine, chemical, HF acid service |
| Nickel 200/201 | ERNi-1 | Chemical processing equipment |
| Hastelloy C-276 | ERNiCrMo-4 | Extreme corrosive environments |
Table 5: Dissimilar Metal
| Joint Type | Recommended Filler | Key Concerns |
|---|---|---|
| Stainless to carbon steel | ER309/ER309L | Dilution, martensite prevention |
| Nickel alloy to stainless | ERNiCr-3 | Thermal expansion mismatch |
| Nickel alloy to carbon steel | ERNiCr-3 | Carbon migration, dilution |
| Copper to steel (corrosion service) | ERCuNi | Galvanic corrosion |
| Copper to steel (decorative/light) | ERCuSi-A | Lower joint strength (brazing) |
Storage note: Aluminum and stainless fillers require clean, dry storage. Low-hydrogen fillers (when applicable) require proper handling to prevent moisture pickup. Avoid contamination from oil, grease, moisture, or shop dirt regardless of filler type.
Fume awareness: Stainless fillers produce hexavalent chromium fume. Nickel fillers produce nickel oxide fume. Aluminum fillers produce aluminum oxide and ozone. Adequate ventilation or local exhaust is required. Use respiratory protection when welding in confined spaces.
