Exploring the Differences between ER70S-6 and ER70S-2 TIG Welding Wire

We train our welders on both S2 and S6 wire.

When it comes to TIG welding, selecting the right filler metal is crucial for achieving strong, clean, and high-quality welds. Two commonly used options for mild steel are ER70S-6 and ER70S-2. While they may seem similar at first glance, each has distinct properties that make it better suited for specific welding conditions.

ER70S-6 TIG Welding Wire

ER70S-6 is a mild steel filler wire known for its high levels of silicon and manganese. These elements help it combat mill scale, rust, and other surface impurities on the base metal, making it a more forgiving option for less-than-pristine welding surfaces.

Key Features:

• Excellent for welding mild and low-alloy steels

• Works well on rusty, oily, or dirty surfaces

• Produces a smooth, stable arc with good puddle control

• Ideal for automotive, structural, and fabrication work

• Popular among beginners for its ease of use

Because of its strong deoxidizing capability, ER70S-6 provides solid welds even in environments where surface prep isn’t perfect.

ER70S-2 TIG Welding Wire

ER70S-2 also meets the same mechanical specs as ER70S-6 but has a different formulation of deoxidizers, including aluminum, titanium, and zirconium. These help control impurities that may be present within the metal rather than just on the surface.

Key Features:

• Best used on clean, prepared base metal

• Ideal for thin materials, like sheet metal and tubing

• Produces precise, high-quality welds

• Excellent puddle control and arc stability

• Often used in aerospace, tube welding, and other precision applications

While it’s not as forgiving with dirty surfaces as ER70S-6, ER70S-2 shines when the base metal is clean and you need tight control over the weld quality.

Choosing Between ER70S-6 and ER70S-2

Factor	ER70S-6	ER70S-2
Base Metal Condition	Tolerant of rust and mill scale	Requires clean surfaces
Material Thickness	Better for thick materials	Better for thin materials
Welding Position	Flat and horizontal preferred	Suitable for all positions
Arc Characteristics	Strong, stable arc	Softer arc with precise control
Deoxidizers	High silicon and manganese	Multiple complex deoxidizers
Common Use Cases	Structural, automotive, general repair	Precision welding, tubing, aerospace
Tensile Strength	70,000 psi (same as ER70S-2)	70,000 psi (same as ER70S-6)

Final Thoughts

Both ER70S-6 and ER70S-2 are excellent choices for TIG welding mild steel. ER70S-6 is versatile, beginner-friendly, and great for general fabrication. ER70S-2, on the other hand, offers better control for thin and clean metals in more precise applications. The best choice comes down to your specific project needs, including the condition of your base metal, its thickness, and the level of weld precision required.

Because of its strong deoxidizing capability, ER70S-6 provides solid welds even in environments where surface prep isn’t perfect.

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About the author: Luis Alejandro is the owner and one of the instructors at Southern Arc Welding Services Ltd. Co.. He enjoys family, reading books on history, and writing to share his knowledge about the many situations welding can place us in.