Welding aluminized steel: Best practices

Q: Which process, filler rod, and shielding gas work best for welding aluminized steel?

A: Aluminized steel resists fire, heat, corrosion, and oxidation. It’s used in many applications, such as weather shielding and exhaust systems. Steel is hot-dipped in an aluminum solution, which provides aluminum qualities on the surface of the cheaper and stronger steel base metal.

Like you do with galvanized steel, which is coated with zinc, you must burn through the aluminum and into the steel. The aluminum coating will melt away, allowing you to fuse into the steel beneath. Don’t let the melting aluminum interfere with the weld pool; this will cause porosity.

You can weld aluminized tubing with gas metal arc welding (GMAW) using ER70-S6 mild steel filler metal and 75 percent argon/25 percent oxygen shielding gas, but this will leave the finished weld zone unprotected because the aluminum will be burned away.

For a corrosion-resistant, completed weld, use one of the 400 series stainless steel wires, such as A1490.

Most of the popular welding processes can be used, but I prefer GMAW because it works well on custom exhaust systems for my high school students’ hot rods.

Make sure you have proper ventilation so you won’t breathe the fumes, and use the correct paint on the finished weld where the aluminum coating has been burned off if you’re using mild steel wire.