alum steel should have a whitish coating, because that's what color alum turns when it oxidizes. galv steel is coated with zinc to prevent rusting.

 

Aluminized and galvanized steels are completely different.
Alunized steel has a thin layer of aluminium over regular carbon steel.
Galvanized steel is coated in zinc and other chemicals to keep it from rusting.

 

Best bet for Mild to Cast is to ARC it. But in order to make it a good weld you need A LOT OF HEAT!!!! So doing anything thin to Cast is near impossible to get a good strong weld. Cast to anything under 3/8" mild is going to turn out like bird ---- piles because you can't place the heat to area long enough to smooth your weld. The Cast is going to absord SO much heat compared to the mild, so you have to use more heat to make up for what the Cast absorbs. Thats why you blow through mild fast. A good bet is to preheat the Cast to a glowing state with a torch. The other problem is the Cast will become VERY brittle afterward and wants to crack. So ideally a Real Welder doing it for a job will preheat, ARC with proper rod, then cool in a bucket of sand for Hours.

I've done a turbo to an adaptor plate with standard 6013 rod with no cracks but I took my time.

As for Galvanized, if you don't grind, you'll pay. I had to touch up an exhaust and all I had available is the stupid patch peices from the parts store, I just welded it Fluxcore. I think I puked everything up that night and was sick for like 2 days.

 

arc weld it with a Ni-rod 99x electrode or something similar, the more nickel content the better.

weld it with Ni-rod 99x and you'll have no problems. no need to preheat or cool slowly when using this

 

You got it. I'm a pipefitter so I do welding like this all day long, and you obviously know what you're doing

you obviously don't know what you're doing

 

I talk from experience buddy . go screw some more pipes together.

 

I've never done it this way. I know it's best. I got this method from a veterain High Persicion Machinist/Welder. I know it's the ideal way, just not always the most functional.

 

Actually, no, there's nothing easier than welding cast. It's just not a strong joint, period.

That being said, I know a couple Muffstank guys who have cast<-->mild joints *supporting* T3's at the end of flipped shorty headers, hold up pretty damn well. Keep in mind, V8's aren't dynamically unbalanced like inline four cyl engines, so a Honduh would shake the turbo hard enough to promote cracking.

My old downpipe was a Saab cast piece cut and flared to 3" mandrel. I bottomed out on the open downpipe twice, sending up enough force to crack my log manifold, before I braced it at the bottom of the engine like I should have in the first place. No problems with the cast-mild downpipe joint...



Oh, yeah, some people are deathly allergic to galvanized steel. Be warned, hotrex's "takes your breath away" might be your trip to the hospital. The two times I welded it, I used a cheap respirator.

 

Welding it to some thinner steal and making it work was a lot harder then welding some thick mild to mild for me. Thats what i meant.

 

Most of the times I've done it, the thin stuff was overlapping the cast and I just punched through it, and it melted together well. The one time I didn't do it that way, I was practiced enough that dumping most of the heat into the cast + shwooping up every so often to stitch the thin wall mild steel tube was pretty easy.

I took most of the basic and intermediate welding classes at the local community college. Good stuff. I was actually pretty good at one point, could have passed most of the welding certs for TIG and oxy/fuel. Not that welding a couple coupons together means you're ready for what the real world brings, but...