telling old stainless from old galvanized? how?

I'm working on boxing the frame rails of my current scratch-built project and am using some 10 ga that came from my grandfather. He's been gone a while and I can't tell if the steel is oxydizing stainless or galvanized. Years ago he said it was stainless and used some of the sheet when he grafted a camaro stub onto his '52 Chev pickup but I would like to be sure before I start welding in my pieces (since welding galvanized is toxic!)

Here's a pic of a leftover piece to show what it looks like now. Any thoughts?

 

Most grades of stainless are not magnetic. Quick and easy way to be fairly sure.

 

If you try to weld it, you will know fairly quickly if it is galv or not.

 

if he was grafting in a sub ,i would think it was steel.

 

All SST steel is slightly magnetic while 400 series SST is very magnetic and will lightly rust similar to the material in your picture due to the higher iron content. You can weld SST to carbon steel but I think I'd buy new material. If it's galvanized steel it will out gas and get a white powdery residue when welded, bad stuff for you health.

 

I agree with Finkster ... buy some fresh metal, then you know exactly what you have and whether or not it can be welded safely as far as weld strength and safely as far as your own health.

 

Metal=cheap.
Hospital=not cheap.
Funeral=not cheap, either.

 

Weld on a piece of it or heat it with a torch. Will be able to know quickly. The galvanized coating will burn off and leave white stuff behind. It is the vapors, smoke, from it burning that is toxic.

Neal

 

If you have some muriatic/Hydrochloric acid around you can apply some of it on to the metal. Galvanized will fizz up almost immediatly. This also removes the layer as well leaving you with raw steel.
This is of course if a magnet doesn't clue you in as to whether its stainless or not.
Always be careful when dealing with acid though!

 

By looking at it, it sure looks galvanized to me... Probably more likely to have left over galvanized than stainless too, cost considered.

 

i don`t think i`d use 10 guage to plate a frame anyway....but just try to grind it or dill it, that`ll tell ya pretty quick...

 

Well I hit the piece with a magnet and it has strong magnetism... I hit it with a piece of sand paper next and a fine, dark gray powder sheeted off of it, so it appears to be galv.

Is it safe to use a flap wheel to remove the coating or would the disk act in similar fashion to a welder and burn off the toxic coating? Does muriatic acid or hydrochloric acid take the coating off completely?

I'm contemplating getting a sandblasting hood and media and taking care of it that way if neither of the above methods would work completely. I already have the pieces cut and fitted well so I'd really rather not "buy new" and start all over again. Rather fix what I have (isn't that what true hot rodding is about anyway?)

 

It is almost impossible to remove the zinc from sheet metal. It creates a toxic gas when welded, a contaminated bead, and paint doesn't stick well to a galvanized surface. A small savings now will come back to haunt you in several areas. The price of a bit of steel and the additional time spent to do the job right the first time will be well respected later in the project. Cheep or used steel is not always the most economical use of time or material. Ask me how I know. The first three rules of welding are clean, clean, clean. It is impossible to adequately clean galvanized steel in the average home or hobby shop.

 

Your galvanized pieces will make good patterns for your new steel. I have gotten sick once from torching galvanized tin and am not excited to work with the stuff again. It is the smoke that gets you. The decision for me would be easy.

Neal

 

If you want to remove or test the galvanizing put a drop of battery acid on it, It will fizz straightaway or if left on will remove for welding. I had to weld a piece of chain recently and a mate told me to use the batt acid.

 

10 gauge is 1/8" which is ideal for boxing a frame.

 

well I ended up going to a local fab. shop and rifling through their scrap steel pile and got two pieces of 1/8" by 8 by 57" pieces for $10 and used the galv. as my patterns. Got the pieces cut and tacked in today.

Thanks for the help on an agent that can remove the coating langy, I do have existing pieces of galv. that have already been grafted onto the frame (not by me) to box the rear that I'll have to mate to...now i know how to get the coating off.

 

Unless you have a pre-paid funeral plan its not likly you'll be paying for your own funeral.

I'm just sayin'

I really love this new millenium. Everything is highly toxic and or deadly.

While I cannot recommend welding galvanized it is probably not nearly as toxic as most are lead to believe. I worked for a galvanized steel and foam dock company for awhile in the '70s. Worked with people that had worked for them for years. One fella was actually retiring from there, he had worked there that long. The frames were built from pre galvanized angle iron. Um I'm still here and lungs are still holding up.

Now one should be aware that that was prior to the time when everyone had a little ventilater, no one wore a respirater.

Like I said I don't recomment using galvanized for a lot of reasons but its not nearly as bad as everyone would lead you to believe. Welding itself is actually a pretty toxic process.

I would try the magnet test, maybe use a scribe on it, stainless will look away different when scribed that galvanized metal. Look for placres that it has been sheared or cut. Is it rusty when it was cut or sheared? galvanizing is a plating or dipping process.

Last resort strike an ark on it or hit it with the torch. Galvanized smells sweet when burning and like as has been mentioned will leave a white residue.

 

i thought navy jelly took galv. right off?

 

I'm siding with Porknbeaner it's not great to weld on because of the amount of flumes but it's not as crazy as you'd think or be lead to believe.
Information is key and this topic has been covered here before.
http://www.sperkoengineering.com/html/articles/WeldingGalvanized.pdf

 

Fiddy if you got jelly in there you got a problem bro. All I ever get out of mine is lint.

 

Billet and Pork'nBeaner
Thanks for the info guys; I thought the "hospital" and "funeral" comment was a bit exaggerated. It's good to know that since I'll have to run a few beads on galv. that I'll be not much the worse for wear if I just wear a respirator and wipe off as much of the coating as i can.

 

Old school welding shops kept milk in the fridge. If you get a wiff of galvanizing fumes and feel nausea, drink the milk.

 

Milk and 'tatters--metal-worker medecine--love it! Thanks for the tip aagie for just in case.