How Magnetic Should Stainless Steel Be?

Joel K

Supporter
Hi everyone,

I am finishing welding up the cooling tubes for the SLC and noticed one of the tubes is significantly more magnetic than the rest. Wondering if perhaps I received a steel tube by mistake. They have been in my basement for three years and haven’t rusted but they have been wrapped up with some bubble wrap the whole time. Just wondering if there is a way to know for sure if they are stainless. I happened to chop that tube up to weld on to other sections and then was using a level to do some final fitting and noticed how much more magnetic those sections were compared to all others.

As always, thanks for the help.
 

Joel K

Supporter
Amazing what you can discover on YouTube. You can accelerate rusting by dipping your metal in a solution of vinegar, peroxide and salt. Sure enough that suspect tube I believe is aluminized steel and not stainless. The ends rusted similar to mild steel and the non magnetic tube did not rust at all.

Well unfortunately I welded in sections from the suspect tube so going to cost me time to re-work it. Geez, always something.

check the results out…
7F5CE1A1-A30D-47E1-B1C0-7D3323858EC1.jpeg
 

Bill Kearley

Supporter
Yes, as Neil said. Many grades of so called stainless. A lot of truck trim accessories made in China are junk an I'v called them on it and received new parts.
 

Joel K

Supporter
Yeah, I did a little more research and learned if stainless is worked it becomes magnetic. For example many of the beaded ends are somewhat magnetic but not nearly as much as the suspect tube. The other thing I was wondering if that one tube was cold rolled and welded if that would make it much more metallic. I sort of want to avoid a lot of re-work so trying to figure out if I’ll have a few really rusted pipe sections down the road,.
 
Wonder if some steel manufacturers shipped lower quality somehow due to covid shortages and just pencil whipped the QA.
 

Joel K

Supporter
Wonder if some steel manufacturers shipped lower quality somehow due to covid shortages and just pencil whipped the QA.
Theses were all shipped with my kit in 2019. Two of the 6 tubes seem to be highly magnetic. I may just finish welding it up as is. If it’s going to rust I’ll see it in a few months then rework those sections.
 

Joel K

Supporter
Well, before I start cutting the cooling tubes apart I took a piece of the suspect tubing, sanded it up and placed it outside. If over the next week or so it doesn’t start to rust I have my answer. Fingers crossed I have no more re-work to do.
 

Terry Oxandale

Skinny Man
Joel, I observed the exact same thing. Ordered a batch of SS tubes for the coolant system (same supplier), and about 1/2 of the tubes had varying degrees of magnetic character. After 10 years, I've not observed any degradation on the inside of the tubes (recently had to drain the system to work on the radiator).
 

Neil

Supporter
If the tubing is only sold as "stainless" it could be any of a dozed different alloys, with varying characteristics.
 

Joel K

Supporter
Thanks everyone for your replies. Well, just to close this thread out I decided to replace the sections of the magnetic tubing. My conclusion is those two pieces are not 304, but some other grade most likely 409. My little experiment leaving the pipe outside Showed some rust after 5 days.

Here is a pic of the tubing vs, Mild steel. The tubing certainly didn’t rust as much as mild steel, but not looking pristine either...
CF1F536B-31C2-4D1F-8AE7-A3AF83A36F9A.jpeg


The area on the side that rusted I cleaned up 5 days ago with a dremel to take any oxidation or coating off…
124EA1B8-90DC-42D4-96A4-981100C4B998.jpeg


Lastly, both magnetic tubes had these ridges down the weld seam. To me, any hose end may have had trouble sealing them so after realizing this decided to replace them with some tubes from Verociousmotorsports. They have very good prices on tubing and will apply the bead ends as required. Now on to finishing the cooling tubes…
32C085FC-EA43-47FB-97CE-0F2A4BCB0C2C.jpeg
 
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Stainless steel is supposed to form a very thin clear coating on its own . Manufacturers of trim use a process to put the clear on or speed up the natural process I'm not sure its been a few years. I fixed up some window trim from 1968 and did a cleaning with a product called bar keeper's friend , it contains an abrasive and acid . From what I remember it takes a few weeks for the clear coating to form . Just some info I learned from restoring trim parts.
 
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