Three filler wires — ER308, ER308L, and ER308LSi — sit side by side on most stainless steel welding wire shelves, and at first glance they look identical. In fact, all three belong to the same 308 family of austenitic filler metals, all three are designed for welding 304-type stainless steel, and all three are classified under the AWS A5.9 standard. The differences are small in name but significant in practice: a change in carbon content and a change in silicon content. Choosing the right er308 welding wire for a job affects corrosion resistance, weld appearance, welding speed, and cost. This guide explains what each wire is, how they compare, and which one to pick for common applications, in plain language that any welder, buyer, or quality engineer can follow.

What Are ER308, ER308L, and ER308LSi Welding Wires?

ER308 welding wire is a solid austenitic stainless steel filler metal with a nominal composition of about 21% chromium and 10% nickel. In the AWS A5.9 classification system, “ER” stands for electrode or rod, and the number 308 identifies the alloy family. These wires are produced as spooled wire for MIG (GMAW) welding and as straight rods for TIG (GTAW) welding, and they are the standard choice for joining 304, 304L, and other 18-8 type austenitic stainless steels. The same family is also used for welding 308-type base metals and for corrosion-resistant overlays. For a broader introduction, this technical overview of the welding of austenitic stainless steel explains the metallurgy behind the 300-series alloys. The letters at the end of the designation carry the real information: “L” means low carbon, and “Si” means higher silicon. Understanding these two letters is the key to choosing the right wire for a specific job.

Chemical Composition — What the Standard Says

The AWS A5.9 filler metal specification sets the chemical composition limits for all three grades. As the table below shows, chromium, nickel, manganese, and residual elements are identical; the differences are limited to carbon and silicon.

Figure 1. Carbon and silicon differences between ER308, ER308L, and ER308LSi (values in weight percent, per AWS A5.9).

Values are weight percent per AWS A5.9. UNS designations: ER308 = S30880, ER308L = S30883, ER308LSi = S30888. Because AWS classifies these wires by chemical composition, any wire that meets the limits above may be labelled with the corresponding classification regardless of the manufacturer.

ER308 vs ER308L — What the “L” Changes

The only difference between ER308 and ER308L is the carbon limit: 0.08% maximum for ER308, 0.03% maximum for ER308L. Why does such a small change matter? When austenitic stainless steel is heated in the range of roughly 425 to 870 degrees Celsius — exactly what happens in the heat-affected zone during welding — carbon combines with chromium to form chromium carbides at the grain boundaries. Because the carbides pull chromium out of the surrounding metal, thin chromium-depleted zones form along the grain boundaries. In a corrosive environment, these zones can be attacked selectively, a failure known as intergranular corrosion or weld decay. The mechanism of sensitisation in stainless steel explains this process in more detail. With a carbon limit of only 0.03%, ER308L simply has far less carbon available to form carbides, so the weld deposit and heat-affected zone stay more resistant to this type of attack.

ER308 remains perfectly suitable for many jobs: general-purpose fabrication of 304, single-pass welds on thin sections, and service in mild, non-corrosive environments. ER308L is the safer choice when the welded part will be exposed to corrosive media such as food processing, dairy, chemical, and pharmaceutical service, when the section is thick or the weld is multi-pass, or when the specification calls for 304L base metal. Many shops standardise on ER308L to cover both cases, since it is approved for 304 and 304L alike and the extra cost is modest.

ER308L vs ER308LSi — What the Silicon Adds

The comparison ER308L vs ER308LSi comes down to a single element: silicon. ER308LSi keeps the same low-carbon chemistry as ER308L but raises the silicon range from 0.30–0.65% to 0.65–1.00%. Silicon acts as a deoxidizer and, more importantly for the welder, it lowers the surface tension of the molten pool. The practical results are better wetting of the base metal, a flatter and smoother bead, a more stable arc, and noticeably less spatter. For these reasons, ER308LSi welding wire is the preferred grade for MIG welding in production environments, where bead finish, travel speed, and downtime for spatter cleaning all affect cost. It also performs well for out-of-position and vertical-down welding because the pool stays more fluid and easier to control.

The trade-off is small but worth knowing. Because the higher silicon is a deliberate addition, some project specifications that control silicon for specific chemical media still call for standard ER308L. For TIG welding, both grades are used; ER308LSi gives a slightly smoother bead on thin sheet, while ER308L is chosen when a specification limits silicon. For most buyers, the practical rule is: choose ER308L when corrosion resistance is the priority and the specification is fixed; choose ER308LSi when weldability, appearance, and MIG productivity matter more.

Mechanical Properties and Weld Performance

AWS A5.9 does not define minimum mechanical properties for these classifications; the numbers below are typical values published by SANZHONG WELD for its ER308, ER308L, and ER308LSi product range, and similar figures are reported across the industry. In practice, all three grades deposit weld metal with comparable strength, and all three contain a small amount of delta ferrite, typically a few percent to roughly 10%, which helps prevent hot cracking during solidification.

The strength figures are manufacturer datasheet minimums for weld metal; actual results depend on base metal, shielding gas, and welding parameters.

Which Wire Should You Choose?

Choosing between the three grades means matching the wire to three questions: what base metal is being welded, what service the part will see, and which process will be used. The table below summarises the most common situations.

Two additional points are worth noting. First, always follow the project specification: if the drawing or welding procedure says ER308L, substituting ER308 is not equivalent because corrosion performance differs. Second, if a weld will be held at sustained high temperature in creep service, the low-carbon L grades are not the answer; stabilised or H-type fillers are used for that purpose. For normal stainless steel fabrication, the three grades above cover the vast majority of jobs.

Shielding Gas and Welding Parameters

ER308, ER308L, and ER308LSi are solid wires and always need shielding gas; none of them is a self-shielded product. For MIG welding, a mixed gas of argon with about 2% oxygen, or 2% CO2, is the common choice, typically set to 20–25 L/min, and it produces a stable arc with minimal spatter. For TIG welding, 100% argon at 8–15 L/min is standard, with an arc length of about 1–3 mm. Cleanliness matters as much as the wire: oil, rust, and moisture on the joint cause porosity and cracking, so the groove and surrounding surfaces should be cleaned to a metallic finish before welding. For corrosion-critical joints, argon back-purge is recommended. Common diameters are 0.8, 0.9, 1.0, 1.2, and 1.6 mm for MIG spools, and 1.6, 2.0, 2.4, 3.2, and 4.0 mm for TIG rods.

Storage and Handling

Stainless filler wires are sensitive to contamination. Spools and rods should be kept in their original packaging — typically 1 kg spools, 5 kg spools, and 15–20 kg spools for MIG, and 5 kg or 10 kg boxes for TIG — in a clean, dry store away from carbon steel dust and moisture. The certificate supplied with each lot identifies the AWS classification, heat number, size, and net weight.

Conclusion

None of the three grades is universally better. ER308 welding wire is the economical general-purpose choice for 304; ER308L adds the low-carbon insurance that protects against intergranular corrosion in demanding service; ER308LSi combines the same low carbon with better wetting and a cleaner bead for MIG applications. The ER308L vs ER308LSi decision, like the ER308 vs ER308L decision, is really about matching the wire to the base metal, the service environment, and the welding process. Check the specification, consider the corrosion risk, and choose the grade that fits. When in doubt, the low-carbon grades are the safer default.

Frequently Asked Questions

What is the difference between ER308 and ER308L welding wire?

The difference is carbon content. ER308 allows up to 0.08% carbon, while ER308L limits carbon to 0.03%. The lower carbon of ER308L reduces chromium carbide precipitation during welding, giving better resistance to intergranular corrosion.

Is ER308LSi the same as ER308L?

Almost, with one difference. Both limit carbon to 0.03%, but ER308LSi welding wire raises silicon from 0.30–0.65% to 0.65–1.00%. The extra silicon improves wetting and fluidity, reduces spatter, and gives a smoother bead in MIG welding.

Can ER308L weld 304 stainless steel?

Yes. ER308L is a common and fully acceptable choice for 304 as well as 304L, and it is often preferred for corrosive service. ER308 is also suitable for 304 in mild environments.

Which is better for MIG welding, ER308L or ER308LSi?

For most MIG work, ER308LSi is easier to weld because of better wetting, less spatter, and a flatter bead. Choose ER308L when the project specification controls silicon or when chemistry limits are strict.

Do these wires need shielding gas?

Yes. They are solid wires, not self-shielded. Use argon with about 2% oxygen, or 2% CO2, for MIG welding, and 100% argon for TIG welding.

Can ER308LSi be used where ER308L is specified?

Not without checking the specification. The compositions are identical except for silicon, so many applications accept ER308LSi, but some chemical-service specifications restrict silicon. Confirm with the responsible engineer before substituting.