AWS A5.10/A5.10M · Aluminum
ER4043 Welding Electrode
ER4043 is the 5% silicon aluminum filler — fluid, crack-resistant and the default choice for welding 6061 and aluminum castings.
- 27 ksi tensile
- Polarity AC (GTAW), DCEP (GMAW)
- 4 positions
- Medium penetration
- TIG (GTAW) / MIG (GMAW)
What ER4043 means
| Part | Meaning |
|---|---|
| ER | Electrode or rod — usable for MIG or TIG |
| 4043 | Aluminum Association alloy 4043, nominally 5% silicon, balance aluminum |
ER4043 specifications
| AWS specification | AWS A5.10/A5.10M |
|---|---|
| Process | TIG (GTAW) / MIG (GMAW) |
| Form | Solid wire / rod |
| Polarity | AC (GTAW), DCEP (GMAW) |
| Welding positions | Flat, Horizontal, Vertical, Overhead |
| Tensile strength (min) | 27 ksi (186 MPa) |
| Yield strength (min) | 16 ksi (110 MPa) |
| Elongation (min) | 8% |
| Impact toughness | Not applicable |
| Coating / core | None — bare wire or rod |
| Penetration | Medium |
| Deposition rate | High on MIG, moderate on TIG |
| Slag | None; remove the oxide layer mechanically before welding |
| Arc character | Fluid and fast, with a narrow window between cold and burn-through |
| Shielding gas | 100% argon |
ER4043 amperage by diameter
Typical operating ranges. Start near the middle of the range, then adjust by sound and bead profile. Reduce 10–15% for vertical and overhead work.
| Diameter | Amperage range | Typical start |
|---|---|---|
| 0.030 in (0.8 mm) MIG | 60–175 A | 118 A |
| 0.035 in (0.9 mm) MIG | 70–200 A | 135 A |
| 3/64 in (1.2 mm) MIG | 100–260 A | 180 A |
| 1/16 in (1.6 mm) TIG | 40–90 A | 65 A |
| 3/32 in (2.4 mm) TIG | 80–130 A | 105 A |
| 1/8 in (3.2 mm) TIG | 120–190 A | 155 A |
Polarity: TIG on aluminum uses AC so the reverse half-cycle strips the oxide layer. MIG uses DCEP, usually through a spool gun or push-pull torch because the soft wire birdnests in a standard liner.
Shielding gas for ER4043
| Gas | Notes |
|---|---|
| 100% argon | Standard for both TIG and MIG on aluminum up to about 1/2 in. |
| 75% Ar / 25% He | Adds heat for thicker sections and improves wetting. |
| 50% Ar / 50% He | Heavy plate and castings where penetration is the limit. |
Flow rate: 20–30 CFH (9–14 L/min); aluminum needs more coverage than steel
What ER4043 is used for
- Welding and repairing 6061 structures, frames and extrusions
- Casting repair on engine blocks, housings and manifolds
- General aluminum fabrication where strength is not the limiting factor
- Heat exchangers and tubing in 3003
- Anywhere crack sensitivity outweighs the need for joint strength
Base metals
- 6061 and the 6xxx series
- Aluminum castings including 356 and A356
- 3003 and 3004
- 1xxx commercially pure aluminum
Characteristics
- 5% silicon lowers the melting point and widens the freezing range, which is what makes it crack resistant
- More fluid than ER5356 — easier to run, wets out flatter
- Finishes dull gray and turns dark if the part is anodized, so it is the wrong choice for cosmetic anodized work
- Lower shear and tensile strength than ER5356
- Not recommended for 5xxx base metals containing more than about 3% magnesium, where Mg-Si compounds embrittle the weld
Storage and handling
Keep sealed and dry. Aluminum filler grows an oxide layer and picks up moisture that turns into weld porosity.
- Store TIG rod in a sealed tube; keep MIG spools bagged with desiccant when out of the machine.
- Handle with clean gloves — hydrogen from skin oils and moisture is the main cause of aluminum weld porosity.
- Wipe rods with acetone and use a dedicated stainless brush on the joint immediately before welding.
- Do not use filler that has developed a visible white oxide bloom.
Welding tips
- On AC TIG, set balance around 65–70% electrode negative for good penetration with enough cleaning action.
- Preheat sections over 1/4 in to 250–300 °F (120–150 °C), but never exceed 400 °F on heat-treatable alloys.
- Clean with a stainless brush dedicated to aluminum immediately before welding — the oxide reforms in minutes.
- For MIG, use a spool gun or push-pull torch with a nylon or graphite liner; a steel liner shaves the soft wire.
- Choose ER4043 when the part might crack and ER5356 when the joint needs strength or will be anodized.
ER4043 frequently asked questions
What is the difference between ER4043 and ER5356?
ER4043 is 5% silicon: more fluid, more crack resistant, easier to weld, but weaker and it anodizes dark gray. ER5356 is 5% magnesium: stronger, better color match when anodized, stiffer to feed, and more sensitive to cracking on some base metals.
Can ER4043 weld 6061?
Yes — it is the standard filler for 6061. The silicon suppresses the hot cracking that a matching 6061 filler would suffer from.
What gas do you use with ER4043?
100% argon for both TIG and MIG on material up to about 1/2 in. Argon-helium mixes add heat for thicker sections and castings.
Why does aluminum TIG use AC?
Aluminum carries a tough oxide skin that melts far hotter than the metal beneath it. The electrode-positive half of the AC cycle blasts that oxide off, while the electrode-negative half puts heat into the joint.
Will ER4043 match the color after anodizing?
No. A 4043 weld anodizes dark gray to black against the base metal. For cosmetic anodized work, ER5356 gives a much closer match.