Match the filler to the base metal: E7018 or ER70S-6 for mild steel, 308L for 304 stainless, 316L for 316, 309L for stainless to carbon steel, 4043 or 5356 for 6061 aluminium and 5183 or 5356 for 5083, and nickel rods (ENi-CI or ENiFe-CI) for cast iron.
This chart gives a starting filler for the common base metals and combinations, by process: stick (SMAW), MIG (GMAW), TIG (GTAW) and flux-cored (FCAW). Find the base metal in the first table, or the alloy combination in the aluminium table, then read the notes, which explain when to change filler. It is general guidance. A welding procedure specification (WPS), code or customer specification always takes priority, and the filler maker's data sheet gives the approved uses for each product. To decode a classification such as E71T-1C or ER308LSi, see the electrode and wire classification chart.
Filler finder by base metal
| Base metal | Stick (SMAW) | MIG (GMAW) | TIG (GTAW) | Flux-cored (FCAW) | Notes |
|---|---|---|---|---|---|
| Carbon and low-alloy steel | |||||
| Mild steel (A36, 1018, S235, S275, S355) | E7018; E6010 / E6011 roots; E6013 light sheet | ER70S-6 (ER70S-3 on clean steel) | ER70S-2 or ER70S-6 | E71T-1C/M; gasless E71T-11 | E70 filler over-matches these steels. Use low hydrogen on thick sections and restrained joints. |
| Galvanised mild steel | E6010, E6013 or E7018 after removing zinc | ER70S-6, or MIG braze with ERCuSi-A | ER70S-2 | E71T-11 | Grind the zinc back from the joint and extract the fumes. |
| Medium carbon and alloy steel (1045, 4130, 4140) | E7018 (under-matching) or E8018 / E9018 low hydrogen | ER70S-6 or ER80S-D2 | ER70S-2 or ER80S-D2 | E81T1-Ni1 / E91T1 types | Preheat and cool slowly; hydrogen control is essential. Check the carbon equivalent. |
| 1.25Cr–0.5Mo (P11, F11) | E8018-B2 | ER80S-B2 | ER80S-B2 | E81T1-B2 | Preheat and post-weld heat treatment are normally required by code. |
| 2.25Cr–1Mo (P22, F22) | E9018-B3 | ER90S-B3 | ER90S-B3 | E91T1-B3 | Preheat and PWHT as the code or WPS requires. |
| Weathering steel (A588, Corten, S355J2W) | E8018-W2 (or E8018-C3 / C1) | ER80S-Ni1 | ER80S-Ni1 | E81T1-W2 | Ni or Cu-Cr fillers weather to a matching colour; single-pass small welds often use E7018 / ER70S-6. |
| Low-temperature Ni steels | E8018-C1 (2.5 Ni), E8018-C2 (3.5 Ni) | ER80S-Ni2 / Ni3 types | ER80S-Ni2 | E81T1-Ni2 | Choose by required impact temperature. |
| Quenched and tempered high strength (A514, S690) | E11018M | ER110S-1 | ER110S-1 | E111T1-K3 types | Control heat input and preheat closely; follow the steel maker. |
| Stainless steel | |||||
| 304 / 304L to itself | E308L-16 (-15, -17) | ER308LSi | ER308L | E308LT1 | L grades resist sensitisation. |
| 316 / 316L to itself | E316L-16 | ER316LSi | ER316L | E316LT1 | Mo for pitting resistance; do not use 308L on 316. |
| 304 to 316 | E308L-16 (or E316L-16) | ER308LSi | ER308L | E308LT1 | Use 316L where the 316 side sees the corrosive service. |
| 321 or 347 | E347-16 | ER347Si | ER347 | E347T1 | Niobium-stabilised filler for stabilised grades. |
| 309 / 309S; 310 | E309L-16; E310-16 | ER309L; ER310 | ER309L; ER310 | E309LT1 | Heat-resistant grades. |
| Stainless to carbon steel | E309L-16 (309LMo type for 316) | ER309LSi (ER309LMo) | ER309L | E309LT1 | Over-alloyed 309L absorbs dilution from the carbon steel and stays crack resistant. |
| 410 martensitic | E410-15/16 with preheat and PWHT; E309L-16 if no PWHT | ER410 / ER309L | ER410 / ER309L | See maker | Preheat about 200–300 °C (390–570 °F). A 309L weld will not harden or match strength. |
| 430 ferritic | E430-16 or E309L-16 | ER430 / ER309LSi | ER430 / ER308L | See maker | Low heat input to limit grain growth. |
| Duplex 2205 | E2209-16 | ER2209 | ER2209 | E2209T1 | Filler over-alloyed in nickel to restore the ferrite balance; control heat input and interpass temperature. |
| Super duplex 2507 | E2594-16 | ER2594 | ER2594 | E2594T1 | As duplex, tighter heat-input window. |
| Duplex to carbon steel | E309L-16 or E2209-16 | ER309LSi or ER2209 | ER309L or ER2209 | E309LT1 | Check the corrosion requirement of the joint. |
| Cast iron, nickel and copper | |||||
| Grey cast iron (thin sections, must be machined) | ENi-CI (99 Ni) | ERNi-CI | ERNi-CI | ENiFeT3-CI | Lowest hardness in the fusion zone, easiest to machine. |
| Ductile iron, thick cast iron, cast iron to steel | ENiFe-CI (55 Ni) | ERNiFeMn-CI | ERNiFeMn-CI | ENiFeT3-CI | Stronger and more crack tolerant than 99 Ni; less sensitive to phosphorus. |
| Copper (deoxidised) | ECu | ERCu | ERCu | n/a | Preheat thick copper (often 200–500 °C); use deoxidised copper base where possible. |
| Silicon bronze; brass; galvanised braze | ECuSi | ERCuSi-A | ERCuSi-A | n/a | Silicon bronze welds and brazes brass and coated steel at low heat. |
| Aluminium bronze; copper to steel | ECuAl-A2 | ERCuAl-A2 | ERCuAl-A2 | n/a | Strong, wear resistant, also used for overlays. |
| Phosphor (tin) bronze | ECuSn-C | ERCuSn-A | ERCuSn-A | n/a | Bearings and bushings, bronze castings. |
No rows match that search.
Flux-cored stainless classes are AWS A5.22 (E308LT1 etc., with -1 or -4 for the gas); low-alloy flux-cored classes are A5.29. Choose cored and nickel products from a maker's catalogue, as availability varies.
Carbon and low-alloy steel
For mild steel, the filler choice is mostly about the process, position and hydrogen level, not strength: E7018, ER70S-6 and E71T-1 all over-match common structural steels. As carbon and alloy content rise, hydrogen cracking becomes the main risk. Use low-hydrogen fillers, preheat and slow cooling. Under-matching filler (E7018 or ER70S-6 on 4140) is common when the joint does not need full base-metal strength, because the softer weld is more forgiving. Work out the carbon equivalent with the carbon equivalent calculator and the preheat with the preheat calculator.
Stainless steel and dissimilar joints
- Same-grade joints: use the matching filler with an L for low carbon: 304 → 308L, 316 → 316L. The filler is slightly richer in alloy and ferrite than the base metal, which prevents hot cracking.
- Stainless to carbon steel: use 309L. The carbon steel dilutes the weld; the extra chromium and nickel in 309L keep the diluted weld austenitic with some ferrite, so it neither cracks nor turns martensitic. Use 309LMo when the stainless side is 316.
- Duplex: duplex fillers such as 2209 carry about 9% nickel against 5–6% in 2205 base metal, so the weld cools to a sound ferrite–austenite balance. Do not weld duplex without filler, keep heat input within the WPS range and interpass temperature low (commonly 150 °C max). Check the weld heat input.
Aluminium base alloy matrix: 4043 vs 5356 vs 5183
| Base metals | First choice | Alternative | Why |
|---|---|---|---|
| 1100 to 1100 | 1100 | 4043 | Pure aluminium: 1100 for conductivity and corrosion, 4043 if it cracks. |
| 3003 to 3003 | 4043 | 1100 | 4043 gives better crack resistance and fluidity. |
| 3003 to 6061 | 4043 | 5356 | Either works; 5356 for a better anodised colour match. |
| 5052 to 5052 | 5356 | 5554 (service above 65 °C) | 5052 has about 2.5% Mg. 4043 can be used on 5052 but gives a weaker, less ductile weld. |
| 5083 or 5086 to itself | 5183 | 5356, 5556 | Never 4043: Mg2Si forms in the weld and makes it brittle. 5183 meets the as-welded strength of 5083. |
| 5083 to 6061 | 5356 | 5183 | Use a 5xxx filler with high-Mg base metals. |
| 5454 to 5454 (hot service) | 5554 | 5356 (below 65 °C only) | Base and filler under 3% Mg for sustained service above 65 °C (150 °F). |
| 6061 to 6061; 6082 to 6082; 6063 | 4043 (or 4943) | 5356 | 4043 for crack resistance, castings and general work. 5356 for higher shear strength, ductility and anodising. |
| 6061 to 5052 | 5356 | 4043 | 5356 preferred for strength. |
| 6061 to cast A356 / 356 | 4043 | 4047, 5356 | Silicon filler for joints to castings. |
| Cast A356 to itself | 4043 | 4047 | 4047 for joints that crack with 4043. |
| 7005, 7020 (weldable 7xxx) | 5356 | 5183 | Weldable 7xxx extrusions, for example bicycle frames and some structures. |
| 2219 | 2319 | 4043 (lower strength) | Heat-treatable 2xxx welding alloy. |
| 2024, 7075 | Not recommended | n/a | Hot cracking: these alloys are generally not fusion welded. Rivet, bolt or bond them. |
The rules behind the aluminium choices
- Crack sensitivity. 6xxx alloys crack if welded without filler or with too little. 4043 has the best resistance to hot cracking; 5356 works if enough filler goes in (keep dilution down with a groove preparation and a good fill).
- Magnesium plus silicon. Do not use 4xxx (silicon) filler on 5xxx alloys with more than about 2% Mg, such as 5083 and 5086: brittle Mg2Si forms in the weld.
- Service above 65 °C (150 °F). Alloys with more than 3% magnesium, including 5356, 5183 and 5556 fillers and 5083 base metal, can become sensitised to stress corrosion cracking in sustained service above about 65 °C. Use 5554 filler with 5454 base metal, or 4043 where the base metal allows.
- Anodising. 4043 welds turn dark grey after anodising; 5356 gives a much closer colour match.
- Strength. 5356 and 5183 give higher as-welded shear strength in fillet welds than 4043. Heat-treated 6061-T6 loses strength in the heat-affected zone whatever the filler; 4643 filler allows the whole part to be re-heat-treated.
Cast iron
Cast iron welds crack because the iron has almost no ductility and the fusion zone forms hard carbides. Nickel fillers (AWS A5.15) stay soft and ductile. Use ENi-CI (about 99% Ni) for thin sections and repairs that will be machined. Use ENiFe-CI (about 55% Ni) for thicker sections, ductile (SG) iron and cast iron to steel, where its higher strength and tolerance of phosphorus help. Steel rods (ESt) are cheap but leave a hard, unmachinable weld.
Clean and preheat the casting if you can, typically 260–315 °C (500–600 °F) for grey iron, and cool it slowly in insulation or sand. If you cannot preheat, weld cold: short beads about 25 mm (1 in) long, peen each bead while hot, and let the casting cool until you can touch it before the next bead. Drill crack ends first so the crack cannot run.
Copper and bronze basics
Copper conducts heat away so fast that thick sections need preheat, often 200–500 °C depending on thickness, and high current. Weld deoxidised copper with ERCu; oxygen-bearing (tough pitch) copper tends to porosity and embrittlement. Brass contains zinc, which boils off as fumes, so it is usually joined with silicon bronze (ERCuSi-A) or phosphor bronze (ERCuSn-A) at low heat rather than fusion welded. Aluminium bronze (ERCuAl-A2) joins aluminium bronze, copper to steel, and makes hard-wearing overlays.
How to use this chart
- Check whether a WPS, code or drawing names the filler. If it does, use that.
- Find the base metal (or both base metals for a dissimilar joint) and the process you will use.
- Read the notes for preheat, heat input and service conditions that change the choice.
- Confirm with the filler maker's data sheet, then run a test piece on scrap of the same material.
Worked example: 6061-T6 bracket to a 5083 plate, anodised afterwards
5083 has about 4.5% Mg, so 4043 is ruled out (Mg2Si). 5356 is the first choice from the matrix for 5083 to 6061, and it also gives a better anodised colour match. If the part runs hot (above 65 °C), redesign with a lower-Mg base such as 5454 and use 5554 filler.
Worked example: 304 stainless bracket on a mild steel frame
Dissimilar stainless to carbon steel: use ER309L (TIG or MIG, ER309LSi for MIG) or E309L-16 rods. 308L would be diluted by the carbon steel and could crack.
Related calculators and charts
Based on the AWS A5 filler metal specifications (A5.1, A5.4, A5.5, A5.6, A5.7, A5.9, A5.10, A5.15, A5.18, A5.20, A5.22, A5.28, A5.29) and widely published filler maker selection guides. This is general guidance, not a procedure: follow your WPS and the filler manufacturer's recommendations, and qualify critical welds.