When it comes to welding, a MIG welder is very forgiving. It has a spool of wire inside and all you have to do is pull the trigger and it lays down a pretty nice weld. If you’re welding different types of metal or need a nicer weld, the TIG welder comes into play. And for that, you need filler rod.
The ER70S-6 is for mild steel. It’s the most common type of filler rod found in an automotive shop and is great for sheet metal, chassis, and suspension components. The -6 at the end means it has more oxidizers in it which helps provide a flatter and quicker bead. It’s an alloy which means it has other metals, like copper and chromium, in it in small quantities. That’s what gives it it’s shiny copper color.
Next up is 308L. This is for welding stainless steel to stainless steel. The most common types of stainless steel in an automotive shop are 304 and 409. It’s an alloy of mostly iron with about 10% nickel and around 20% chromium.
If you’re going to weld stainless steel to mild steel, you’re going to need 309L as it’s ideal for wearing non-similar steel. It’s made up of 13% nickel and 24% chromium along with other additives. You can also use 309 for welding similar alloys like 304 stainless to 409 stainless.
There are two others that aren’t as popular but still used. One is aluminum which is only good for welding aluminum to aluminum. Silicon bronze, on the other hand, will do just about anything. You can weld steel, bronze, brass, or any combination. Just remember it won’t be as strong as a regular steel weld…