Choosing the right filler wire is one of the simplest ways to prevent defects and get the mechanical properties and corrosion resistance you need. As a rule, match the filler to the parent material and application: ER70S-6 for most mild steel MIG work, ER70S-2 for mild steel TIG, 308L-family fillers for 304 stainless, 316L for 316 stainless, and ER4043 or ER5356 for aluminium depending on the alloy and service conditions.
This guide compares the filler wires welders most often have to choose between, side by side.
ER70S-6 vs ER70S-3 — which is better?
ER70S-6 and ER70S-3 are both solid mild steel MIG wires, but ER70S-6 contains higher levels of manganese and silicon. This allows it to weld through light mill scale and minor surface contamination more effectively than ER70S-3.
For most fabrication, structural steel and general engineering applications, ER70S-6 is the preferred choice because it offers better arc stability, improved bead appearance and greater versatility.
ER70S-2 vs ER70S-6 TIG rod — which for mild steel?
ER70S-2 contains additional deoxidisers that improve weld quality on steels with minor surface contamination. ER70S-6 contains higher manganese and silicon levels and is more commonly associated with MIG welding applications.
For TIG welding of mild steel, ER70S-2 is generally the preferred filler rod.
Copper-coated vs copper-free MIG wire
Copper-coated MIG wire improves electrical conductivity and helps protect the wire from corrosion during storage. Copper-free wire reduces copper deposits inside liners and contact tips, making it popular for robotic and automated welding.
Both produce excellent weld quality when manufactured to high standards. The best choice depends on your welding equipment, production environment and maintenance preferences.
0.8 mm vs 1.0 mm MIG wire
A 0.8 mm wire is ideal for thin to medium thickness steel and offers excellent control with lower welding currents. A 1.0 mm wire provides higher deposition rates and deeper penetration, making it more suitable for thicker fabrication.
Choose the wire diameter according to the material thickness, welding current and production requirements.
1.0 mm vs 1.2 mm MIG wire
A 1.0 mm MIG wire is commonly used for general fabrication and medium thickness steel, while 1.2 mm wire is designed for heavier fabrication where higher deposition rates are required.
Larger wire diameters generally improve productivity on thick materials but require more powerful welding equipment.
Solid wire vs flux-cored wire
Solid MIG wire produces clean welds with minimal slag and is ideal for workshop fabrication using shielding gas. Flux-cored wire offers deeper penetration and higher deposition rates, making it better suited to thicker materials and outdoor applications.
The best choice depends on your welding environment, material thickness and productivity requirements.
308L vs 308LSi TIG wire
Both are designed for welding 304 stainless steel. The “Si” in 308LSi indicates a higher silicon content, which improves weld pool fluidity and bead appearance.
For most TIG applications, standard 308L filler rods perform exceptionally well, while 308LSi is more commonly associated with MIG welding where improved wetting characteristics are beneficial.
316L vs 316LSi TIG wire
Both consumables are intended for welding 316 stainless steel. The higher silicon content in 316LSi improves weld fluidity and bead appearance, making it particularly suitable for some automated and high-productivity applications.
For most manual TIG welding, 316L remains the standard choice.
308L vs 316L TIG rod
308L filler rods are used for welding 304 and 304L stainless steel. 316L filler rods contain molybdenum, providing improved corrosion resistance for marine, food processing and chemical applications.
Always match the filler rod to the parent material wherever possible to maintain corrosion resistance and mechanical properties.
308L vs 309L TIG rod
308L is used for welding 304 stainless steel, while 309L is designed for joining stainless steel to carbon steel and other dissimilar metals.
If you’re welding stainless to mild steel, 309L is generally the correct choice because it accommodates the different material properties.
308L vs 309L filler wire
308L filler wire is designed for welding 304 stainless steel. 309L filler wire is formulated for joining stainless steel to carbon steel and for some dissimilar metal applications.
Using the correct filler wire helps maintain weld integrity and long-term performance.
309L vs 312 filler wire
309L is commonly used for joining stainless steel to mild steel. 312 filler wire contains higher chromium and nickel levels, making it suitable for difficult-to-weld steels, repair work and applications where the parent material is unknown.
Technical advice is recommended when selecting filler metals for specialist repairs.
4043 vs 5356 aluminium filler wire
ER4043 provides excellent weldability, low crack sensitivity and a smooth weld appearance. ER5356 offers higher tensile strength, improved corrosion resistance and is often preferred for marine and structural applications.
The correct choice depends on the aluminium alloy and service conditions.
4047 vs 4043 aluminium filler wire
ER4047 contains a higher silicon content than ER4043, providing greater fluidity and lower melting temperature. It is often used where crack resistance and reduced shrinkage are important.
ER4043 remains the most common choice for general aluminium fabrication.
Get the right filler wire for your job
Matching the filler wire to the parent material is the foundation of a sound, corrosion-resistant, crack-free weld. If you’re unsure which wire suits your material, thickness or service conditions — particularly for dissimilar joints or specialist repairs — it’s worth getting it right first time.
Browse the full range in our welding consumables guide, or contact the Weldability SIF technical team for a recommendation.