Can Tin Coated Copper Wire Be Magnetic?

I was under the impression that all metals have some magnetic susceptibilty.

Suggest you google magnetic susceptibility of tin..copper etc.

I am afraid the Dell the Cat is very right. The part is made of wire, coated or not wire will be subject to a magnetic field.

Perhaps they are trying to bamboozle you and get the work for free??

As in a Motor / armature effect

Hi,

if they claim that the piece is magnetic they should disclose how they measured and what field strength and which direction of field strength. (Some measure flux density that can be converted to field strength in air by B=µ.H)

I experienced once a magnetisation of nonmagnetic stainless steel by cold deformation.

Another possibility may be some iron or iron-oxide content inside the copper or tin.

And there exist some strange magnetic alloys, may be you discovered a new one.

RHABE

The part of the magnetic stainless steel I get, but copper and tin forming a magnetic alloy with nobody noticing it before?

I would assume that they did an after treatment which deposited some ferro metal on the part.

Did you check on what they send back or on your own stock?

Start asking the parts back and check it.

A copper wire in a magnetic field will have some induced current when it forms a closed circuit, this could be what happened.

I would think not unless there was current flowing through it.

I would get the exact sample they tested. Either something has been inadvertantly switched or the copper is contaminated with iron.

MAD:

If they are moving their magnet, they're setting up eddy currents in the wire (a conductor) which produce magnetic fields. Any motion of the wire, then, could be the result of the magnetic fields interacting. If there is attraction when everything is still, then there must be real ferromagnetism.

DickL

So this morning i got material off the spoil the wire come form and bent a piece and put it on a pivot point and brought a earth magnet to it and presto the wire rotated from magnetism.

The wire is .032 diameter material is OFHC 102 COPPER ALLOY specifications is ASTMB 3 the chemical properties are CU 99.95%

So is this material reject able or is it saying .05% can be iron .I'm searching the net now please advise any info that may help me with this.

thank you

Does it follow the magnet or just starts to move when the magnet passes by?

It can contain up to 4ppm Fe and 4ppm Ni (copper 102 = oxygen free copper)

Will these contents invoke magnetism? Start with a chemical analysis and when nothing is wrong there the final customer has to accept it. (if he did not specified it better)

http://www.copper.org/resources/properties/144_8/144_8.html

MAD:

My question is, still, did it rotate only when the "earth magnet" was moving, or did it rotate while the magnet was still?

DickL

MAD:

From out of left field, could this possibly be electrostatic repulsion? I still get sparks when leaving my car in this dry weather. Check by touching the magnet to the wire and seeing if the movement still takes place afterward.

DickL

Check out Lorentz Force. Bassically, when a permanent magnet is moved relative to a conductor, it causes a current to flow in the conductor, which, in turn creates a magnetic field in the opposite direction.

In the case of a conductor which is not a loop, the current will be a transient which quickly dissipates due to its inability to continue past the end of a suspended wire, for example, and the only way it can exist at all is due to the inductance of the wire itself.

If the customer is making a loop of the wire, then they are messin' with you, 'cause in that case, the current has a complete path.

I have to agree with the responses that lean toward this explanation. Pure Silver, Copper & Gold (the best conductors of electricity, in order) are actually DIAMagnetic, and are actually slightly repelled by a magnetic field. Tin (like magnesium, lithium, tantalum and molybdenum) is slightly PARAMagnetic, meaning it exhibits only a slight tendency to concentrate lines of magnetic field within itself.

Between the slight induction taking place when the magnetic field is brought into proximity with the wire (at which time, current {or charge} is occuring in the wire ONLY while the lines of magnetic force are MOVING thru it) ... and the 'ever-so-slight' magnetic field associated with that induction (which will always be in opposition TO the field inducing it) ... I believe that a miniscule, though measurable, effect is in fact taking place.

But I assume that the effect is never noticed before.

OR the customer changed the WOW in the assembly. (which is in most cased the reason for such trouble)

OR there is something different with the actual alloy that was not present before.

Mad to answer.

Hi MADMACHINE,

First off since I haven't corresponded with you before welcome to CR4, the best site on the internet for us engineer types to show we really do know what we are talking about and can solve all the world's problems if only people would listen to us.

I think DickL has hit the nail on the head. When you have a moving magnetic field interacting with a conducting medium it will try and induce a current in that medium that in turn produces a magnetic field that will oppose the existing magnetic field. Now the thing is you don't need a complete circuit as the you can get what is called eddy currents. These are like little whirlpools of electric current flowing within the material and when you add them all up they tend to cancel out in the centre of the material and add together forming a current that flows around the surface of the conductor.

The performance of transformers and electric motors can be severely impacted by eddy current and commonly employ various techniques to limit them. The most common and effective way is to laminate the core so that the distance the currents can flow before they hit a non conductive layer is limited. This is the main reason the magnetic core of transformers and electric motors are constructed of layers of thin sheets rather than a solid piece of metal.

The other thing to remember is that materials fall under one of two magnetic categories, magnetic or diamagnetic. You will no doubt be familiar with magnetic materials. These are the materials that are attracted to a magnet like iron and cobalt. Diamagnetic materials are the exact opposite and are repelled by magnetic fields. Most people never know about the diamagnetic properties of materials as the diamagnetic effect is several orders of magnitude less than the magnetic properties people are familiar with, so, if you don't specifically look for them and use very powerful magnets and highly sensitive equipment you would never see them. The photograph on the right is of a frog, which is primarily diamagnetic, being levitated within an extremely intense magnetic field. The filed repelling the frog from all sides and is creating a force strong enough to cancel out gravity.

Since you are talking about something that has very little mass and has its weight supported by a string there is a possibility that what you are seeing is actually a diamagnetic property rather than a magnetic property.

Run a magnetic test on the Sn and Cu materials first, to determine if one or both are magnetic, if one or both are magnetic, run a chemistry on the Sn and Cu separately, you may not have the proper material to begin with. Sometimes you could also create magnetism by cold working the materials to some extent...

Thank you all for your replies your all very intelligent .anyhow I'm not making a closed loop i moved the magnet to the part in a straight motion and saw the affect and after this and your comments i took a part and removed the tin coating from half the part and the side without tin had no movement at all ,the same part with tin coating on it the magnet pulled so it has something to do with the tin coating .i called the supplier and got the plating certification on the tin coating i got back MATERIAL OFHC PLATING TIN THICKNESS .0002 the WIRE company gave us the certification earlier and seem correct.is there a standard allowably magnetic material level for tin coatings. By the way they asked for a solderable tin coated copper wire ofhc 102 copper alloy. please reply with anymore info so i can close this chapter

thank you all

You have confirmed the tin (which is paramagnetic) to be the culprit. The paramagnetism is a quality of the element itself. I know of no way to negate it (short of elevating it to its Curie temperature... and keeping it there!). The denser the lines of magnetic field to which it is subjected, the greater will be the effect upon it. Tho the effect will always be much less than the effect on a ferromagnetic material, it will remain measurable nonetheless. This might well be one of those CLASSIC cases of either "The Spec is Wrong", or the original "Design Didn't Take Everything Into Consideration". IF the miniscule paramagnetic effect of the tin truly affects the end-product in an adverse way, then perhaps a different means of soldering/brazing the (O2_pure) copper should be sought.

Only alloys made with the following metal composition

A test was made using an 8" length of 0,023" tinned coper wire. Mil. spec stuff from 1950's surplus. A series stack of 2-1" spneres and 3 odd shape 3/8" thick rare earth magnets had NO effect on a hair pin shaped piece supported by a small loop in another piece of the same wire.

Any possibility that there are traces of iron or something else in either the wire or the tin coating? Have analytical tests been done by the lab?

Perhaps nickel in plating?

If you follow the link in post #18 there are some interesting compounds that contain copper oxide and are magnetic so maybe there is something happening between the tin and copper that is causing an oxide layer to build up. As rbwhite101 stated perhaps the tin plating is contaminated with small amounts of nickel, chrome or cobalt.

Or Manganese

Hi Gwen,

I think you are right, manganese will give together with copper and tin one of the alloys that are called Heusler-alloys, magnetic alloys in a composition that show no magnetic property as individual materials.

Magnetism is meant here as ferro- or antiferro-magnetic both looking to the outside investigator as ferromagnetic.

RHABE

I think most of the last many posts are on the right track. I have a little different take on it but along the same lines. Did he say mono-crystaline 99.99% pure copper? As a conductor it can definitely have eddy currents induced in it which will then create a magnetic field, when there is a moving magnetic field around it. Also the thin and uniform skin of tin around it being paramagnetic has a tendency to react to the extremely high magnetic field even when the field is stationary. then there are a couple of other factors.... was the copper cleaned with Chromic acid? ( Chromium is "Ferro"magnetic) or was the tin applied in some other solution such as stanous flouride?,... ( the mention of copper oxide in super conductors,... but a very thin layer of stanous flouride could have a similar effect,... also is the tin plate extremely thin and uniform. The conjoining of dissimilar metals especially with mono crystaline copper may effect some rectification of any electromagnetically induced eddy currents in the copper. This could be from ambient light (a photo electric effect) or just ambient Radio Frequency fields or perhaps the slightest motion of the rare-earth magnet, or cell phone background radiation or whatever. A tube of very thin tin around a column of mono chrystaline copper may then have unequal forces axially, versus radially.

I'm guessing annealing the copper, which is done the opposite of steel ( by sudden heating and cooling, and possibly adding a thicker and less uniform, coating of tin, not by plating but by immersing in molten tin, will eliminate this effect. I think it has to do with the tin being so thin it acts as a rectifier with the copper, and the copper is carrying the eddy currents so it is acting sort of like a maglev train, or an induction motor. If the tin is a lot thicker (like several thousands of an inch), the eddy current within the tin will reduce this magnetic compass needle effect, if I am correct about the interaction between the two metals.

I have found that brass connectors (tin and copper) for audio electronics often will rectify radio frequency broadcasts, creating interference in audio electronics. Off course I also remember a physics class demonstration of the effect of a strong magnetic field, slowing the movement of a sheet of aluminum or copper, through it. I'm also remembering how a loop of copper with low voltage, high current of a soldering gun, reacts to a neodymium speaker magnet even when several inches away.

Geoffrey Reed