So I've been using the wrong flux for aluminum for like two years

Honestly, I felt like a total goof. We had this big job in Toledo, a custom run of about 500 decorative castings, and the metal just kept coming out grainy and full of pits. My crew and I were chasing our tails for a week, checking temps and mold prep. The tip off was when our new guy, fresh from trade school, quietly asked if we were using a sodium-based flux. I said yeah, the big green tub we always get. He just nodded and said his teacher swore by a chloride-based one for aluminum, that the sodium stuff was more for iron. I looked at the tub label and sure enough, it said 'For ferrous metals' right on the side. I'd been grabbing it off the same shelf for so long I never read it. We switched and the next pour was smooth as glass. Has anyone else had a 'duh' moment with a basic material like that?

3 comments

3 Comments

emery96510h ago

Been there, grabbed the wrong can of gas for the welder for months.

gavinhunt9h ago

That sodium flux will still work on aluminum in a pinch, it just leaves a nasty crust you have to chip off. The chloride stuff is cleaner. @emery965, wrong gas is a classic too, gives you that sooty bead that just won't lay flat.

coleman.avery6h ago

Man, that's a rough one to find out after two years... but at least it got sorted. Actually, the sodium flux isn't just for iron, it's more for copper alloys like bronze. That's probably why it was such a mess on aluminum, it's made for a totally different family of metals. The crust it leaves is brutal to clean. Good on that new guy for speaking up, those little details from school can save so much headache.