Proper magnets for testing Stainless Steel Scrap

[hyderconsulting]

While I'm thinking of magnets at the moment be careful what you use as a testing magnet for testing a piece of steel to see if it is stainless or not. Don't use a NIB magnet (Neodymium Iron Boron magnet) for testing for it is too strong. Most scrap yards consider scrap steel to be stainless if it is non-magnetic or just slightly magnetic. If you use a NIB for testing you will be culling out steel which the scrap yards would take normally. I know that a lot of scrappers like to use these because they find them easily by dismantling hard drives. Use a regular iron based magnet which is what they used at the scrap yards. You can purchase them at a lot of tool supply stores. Also for the same reason don't use a very, very large iron magnet like a horseshoe magnet as big as a coffee can. They are too strong also. Regards, Chris Hyder.

 

[Geo]

a more reliable test for stainless steel is to hit it with a grinder. the sparks made will tell you what type of steel it is and if you get good enough you can just about tell how much nickel is in it by the spark it throws. a big spark stream with a lot of yellow and red is iron with less sparks and lighter colors the more nickel it contains. inconel and monel have their own unique spark, again it takes practice with known metals to get good at it.

 

[RESET]

Thread resurrection.
Is there an acid test for aluminum and stainless? Could I use HCl? I think I remember that HCl reacts with steel and not aluminum. Some stuff I can tell easily but some of the sheet metal that I come across is hard. I would rather put a drop of acid on the material than haul it all out to the garage to test with the grinder.

 

[Geo]

hcl reacts violently with aluminum. any of the soft, light metals can be mistaken for aluminum (zinc aka diecast and pot metal,titanium although it is very hard).a good chemical test to determine if a metal is aluminum or zinc is to scratch a spot and spray vinegar on it with a spray bottle.zinc will react violently while aluminum will react minimally and stainless will not react at all. aluminum is soft and can be cut easily with a knife blade while stainless steel is much harder and though it can be scratched, you cant cut off flakes like you can aluminum.titanium is light and resembles aluminum in almost every way except in hardness.titanium can not be cut with a knife blade.aluminum makes a dull ringing sound when struck while titanium has a rich clear long lasting ring when struck.

 

[gold4mike]

My local scrap yard uses Nitric to distinguish between Aluminum and Stainless Steel. It's usually easy enough to tell simply by the weight of it but, when in doubt, she uses a drop or two of Nitric.

My biggest source of stainless steel lately has been hard drive covers. Some are aluminum, some steel, some stainless, some are two of the above glued or sandwiched together.

 

[RESET]

The vinegar test sounds perfect. Thanks Geo. Now I can tell pot metal from cast aluminum too, bonus. I usually just try to break the casting, aluminum is harder to break than pot metal in my experience. Now I will have to find cast aluminum and pot metal of the same thickness to test my breaking theory.

EDIT: The stainless/aluminum I have trouble with is the thin stuff. Some times it just seems really light no matter what it is made of. Like heat sink fins, are they all aluminum? I have some that are thin sheet metal attached to a tinned copper base plate. I had to do the slice test to make sure it was aluminum and even then I wasn't convinced.

 

[Geo]

if the base of the heat sink is copper, the fins should be copper too.every copper heat sink ive found without exception was copper on all parts whether it was PC or power supply. i have found a couple of brass heat sinks on older power supplies but the entire heat sink was brass.

 

[RESET]

These are assembled heat sinks on Processors. Some of the bases are aluminum with a small copper plate in them some are solid copper. the fins are sheet metal bent like a square wave and attached to the base I have some with copper fins and some with aluminum. I have heard that they are taken at the scrap yards and treated like radiators. I have no plans on trying to separate the copper from the aluminum so that is how I am going to present them to my yard, as copper/aluminum radiators, really small ones, LOL.