Is ER70S-6 Copper Coated Wire Fully Copper?

The answer is: No, ER70S-6 wire is not fully copper. It is a mild steel wire with a thin copper coating.

Here’s a detailed breakdown:

1. The Core: Steel Alloy

The vast majority of the wire's mass (over 98%) is a steel alloy. The "ER70S-6" classification tells us exactly what this steel is made of:

• ER: Stands for Electrode or Rod.

• 70: Indicates the minimum tensile strength of the weld deposit is 70,000 psi.

• S: Signifies it is a solid wire (as opposed to a flux-cored wire).

• 6: This is the most important part. It designates the specific chemical composition of the steel, which includes added elements like manganese and silicon (and sometimes small amounts of others) that help deoxidize the weld pool, improve arc characteristics, and wetting action.

  
  

2. The Coating: Thin Copper Layer

The wire has a very thin, micro-scale layer of copper electroplated onto its outer surface. This coating serves several critical functions:

• Corrosion Resistance: Prevents the steel core from rusting during storage.

• Improved Conductivity: Copper is an excellent conductor of electricity. This coating ensures smooth and consistent feeding through the welding liner and gun, and provides better electrical contact at the contact tip, leading to a more stable arc.

• Reduced Contact Tip Wear: The smooth, conductive copper layer is much less abrasive on the copper contact tip than bare steel would be, significantly increasing the tip's lifespan.

  
  

Analogy: A Copper-Plated Penny

Think of it like an old-fashioned copper-plated penny (in the U.S., pennies made after 1982 are zinc cores with a copper coating). The entire object looks and feels like copper, but its internal structure is a different, cheaper metal. ER70S-6 wire is the same concept—a steel core for strength, with a copper shell for performance and protection.

Comparison Table

How to Tell the Difference Visually

If you were to cut an ER70S-6 wire and look at the cross-section, you would clearly see two distinct layers:

• A bright silver (steel) center

• Surrounded by a thin gold/bronze-colored ring (the copper coating).

If you file or sand off the surface layer, the bright silver steel will be exposed underneath.

In summary: 

ER70S-6 is a copper-coated steel wire. The copper is only a surface treatment to enhance its welding performance and shelf life; the wire's structural integrity and purpose come from its steel core.

If you need sourcing the ER70S-6 Solid Welding wire,try to send email to us: sales@szewelding.com

We are a factory for more than 15 years exporting experience,and also can make a one-stop welding solution for you.