plating, anodizing, & finishing Q&As since 1989
Copper disguised as magnetic steel to fool me
April 30, 2012
Q. Hi guys. I'm in the scrap metal business. There is foul play within my men and the different places I pick up scrap. My regular customers are power plants, smelting plants and steam turbines. My men and the men from my customers' have found a way to trick me by purposely corroding and pitting the non-ferrous alloys so that when I inspect them in the yard with a magnet, it sticks. Turbine bearings and copper bars look just like regular metal and stick to a magnet. I know this because I have seen copper that looks like flat bars.
If I can't get nitric acid because I don't have the permits, how do I bright dip them or clean them? And most of my non-ferrous that gets purposely tarnished, also become magnetic. How do I also bring them back to non-magnetic? Please help meJiggy Selma
A. I don't get it. Copper, copper alloys, aluminum and most other naturally non-magnetic metals are more expensive by weight than scrap steel. So, in a sense, they're doing you a favor. Pay a bonus for finding and sorting out those metals.
Monterrey, NL, Mexico
A. Hi Guillermo.
I, too, am a little confused. But I have to assume that scrap is leaving Jiggy's yard as if it was steel, and he is only being paid for it as if it was steel, even though he believes it is copper, both from his periodic testing and due to its source.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. It is not possible to to make metals like copper or aluminum magnetic just by corrosion. They need to be alloyed with some magnetic material like iron, nickel, cobalt etc. In any case corrosion would be only on the surface. You can just machine a small piece and 'see' what is inside!H.R. Prabhakara - Consultant
Bangalore Plasmatek - Bangalore Karnataka India
A. Most of them are copper or bronze castings.
Any bright dips or grinding methods I should know about? Is there like a lacquer or magnetic paint out there I should be researching to remove? What's a formula I need to take out anything that magnetizes them? Are there bronze castings out there that when after being filed with a metal file, it is not a bronze or gold color when being reflected with light or the sun?
Please note that all these machineries and metals were from a smelting plant from America from the 1960's. They are all Westinghouse, Allis Chalmers, etc. Thank you guys.