What are these wheels made out of?

[MaximRecoil]

They are the factory wheels from a 2002 Buick Park Avenue. They appear to be ordinary aluminum alloy wheels, albeit chrome plated on the front, but a magnet sticks to them. It doesn't stick to them as strongly as it would to a steel wheel, but it sticks to them nonetheless. I thought maybe it had something to do with the plating, but the magnet also sticks to them on the back where there is no plating, and it doesn't stick to the plastic center caps (not shown in the picture) which have the same chrome finish.

A magnet didn't stick to any other aluminum alloy wheel that I tried, such as the stock aluminum alloy wheels on an '01 Ford Focus, the American Racing Vector wheels on my Charger, or anything else that was at the garage that day, nor did I expect it to.

[Indygenerallee]

The whole rim is chrome plated aluminum. Also the center cap is more of a painted chrome that manufacturers use a different process vs. the process to chrome plate a rim.

[MaximRecoil]

The whole rim is chrome plated aluminum.

No, it isn't. Only the front is chrome-plated, and it stops at the outer lip where the wheel weights are hammered on (i.e., the outer lip on the front is not chrome-plated). None of the rest of the wheel is plated with chrome or anything else.

Also the center cap is more of a painted chrome that manufacturers use a different process vs. the process to chrome plate a rim.

It is chrome-plated plastic which exactly matches the chrome on the face of the wheel. There are various methods for chrome-plating plastic, but either way, the magnet stuck to the wheel on back where there is zero plating of any kind, so the center cap doesn't really matter.

By the way, I have a bicycle with chrome-plated aluminum alloy rims, and a magnet doesn't stick to those either.

[twodko]

All y'all are wrong. It's elfin metal made only in Elfindor crafted by.......elves!

They make cookies too.

[Indygenerallee]

  with some of that special UNOBTANIUM!!! 

http://www.calchrome.com/Home

[draftingmonkey]

I believe Indygenerallee is correct that these are Aluminum Alloy. Scrub the inside of the rim and you may find it is dirty brake dust encrusted chrome plating. Take a look at this  http://www.originalwheels.com/buick-wheels/parkavenue2002rims.php , #4036 looks like yours.

[MaximRecoil]

I believe Indygenerallee is correct that these are Aluminum Alloy. Scrub the inside of the rim and you may find it is dirty brake dust encrusted chrome plating. Take a look at this  http://www.originalwheels.com/buick-wheels/parkavenue2002rims.php , #4036 looks like yours.

There is absolutely no chrome plating or any other plating of any kind anywhere on the wheel except for the front face. The difference in appearance between aluminum and chrome is obvious when viewing in person. Chrome has an entirely different hue and level of sheen than aluminum. Even aluminum that is polished to a mirror finish doesn't look like chrome. Additionally, the chrome was peeling badly on one of the wheels, so even if you couldn't tell the difference between chrome and aluminum simply by looking, you could tell where the chrome ended on that wheel easily enough.

Also, as I've already mentioned, I have chrome-plated aluminum rims on my bicycle, and a magnet doesn't stick to those at all. Chrome itself isn't ferromagnetic, but there is usually a nickel layer beneath chrome plating on aluminum, and nickel is ferromagnetic. However, it is such a thin layer that you can't detect any magnetic attraction to it. You can try it yourself with a nickel (U.S. 5-cent coin); even though its composition is 25% nickel, you won't feel any attraction to a magnet. You can also try it on some chrome-plated pot metal, such as an old car radio faceplate or hood ornament; those are also typically plated with copper, then nickel, then chrome, the same as is done for aluminum. Plastic with real chrome plating has a nickel layer too; good luck trying to get a magnet to stick to that:

The other alternative is to really chrome plate it. This is done by first picking a suitable plastic (usually ABS), then etching it to give the surface 'tooth' for adhesion, then electrolessly applying a conductive layer, then copper plating, then one or more layers of nickel plating, then chrome plating. Chrome plated plastic is a very robust finish, able to withstand abrasion, thermal cycling, and cleaning. Countless millions of automobile grills, taillight bezels and headlamp surrounds have been plated this way.

Emphasis mine

Of course, this doesn't actually matter in this case, because these wheels are absolutely not plated with anything anywhere except for the front face. And yes, they do look exactly like aluminum, so the only thing I've been able to come up with is this:


Strengthening Aluminum Scrap by Alloying with Iron

That article raises two possibilities. The first, as suggested by the title, is that whoever manufactured the wheels intentionally alloyed the aluminum with iron for additional strength. The second, as suggested by this excerpt ...

Iron is the most common impurity found in aluminum. It has a high solubility in molten aluminum and is therefore easily dissolved in the liquid state of aluminum, however its solubility in the solid state is very low (~0.04%). The low solubility of iron in the solid state is accompanied by decreased ductility as a result of the formation of intermetallic phases like FeAl and/or Fe3Al. These intermetallic phases increases the strength of the aluminum alloy they also enhances corrosion resistance. [4,5].

The most difficult elements to control in the recycled aluminum is Fe and Si and these elements tend to increase slightly the more often the metal has been recycled. Fe in particular has a higher tendency to increase gradually in metal recycled over and over again, primarily from pickup from scrap handling systems. As a result, Fe is an ideal candidate for application to alternative products, a good example of which is the use of increased Fe content in aluminum as a deoxidizing agent for steel production. This would benefit both the aluminum and steel industries and add to the life-cycle benefits of aluminum operations [6]. Another example of using high Fe bearing aluminum is to make use of the affinity of Zr for Fe, creating a heavy particle readily taken from an aluminum melt [6].

Emphasis mine

... is that the manufacturer used crappy aluminum that had been recycled many times, and it ended up with enough iron (Fe) content to weakly attract a magnet. That's probably the more likely of the two. The iron impurities idea would also explain why the magnetic attraction felt a little stronger on some parts of the wheel than others (e.g., on the back of the wheel, the magnetic attraction felt stronger toward the outer rim than toward the hub opening), because impurities aren't necessarily evenly distributed.

[Indygenerallee]

 

[John_Kunkel]

There is absolutely no chrome plating or any other plating of any kind anywhere on the wheel except for the front face. The difference in appearance between aluminum and chrome is obvious when viewing in person. Chrome has an entirely different hue and level of sheen than aluminum. Even aluminum that is polished to a mirror finish doesn't look like chrome. 

Chrome plating only shines when the underlying material is polished, chrome that hasn't had the underlying material polished has a dull satin appearance. Both finishes can appear on the same part.

[bill440rt]

The part gets dunked in the copper/nickel/chrome bath during the plating process. How do they only plate 1/2 of the part??     

[MaximRecoil]

There is absolutely no chrome plating or any other plating of any kind anywhere on the wheel except for the front face. The difference in appearance between aluminum and chrome is obvious when viewing in person. Chrome has an entirely different hue and level of sheen than aluminum. Even aluminum that is polished to a mirror finish doesn't look like chrome. 

Chrome plating only shines when the underlying material is polished, chrome that hasn't had the underlying material polished has a dull satin appearance. Both finishes can appear on the same part.

I'm aware of that. It doesn't change the fact that chrome has a different hue and sheen than aluminum. All metals have their own hue; i.e., steel doesn't look like aluminum; aluminum doesn't look like silver; silver doesn't look like chrome; chrome doesn't look like nickel, and so on.

1. The wheels are absolutely not plated anywhere other than on the face. They are not even plated on the outer lip where the wheel weights mount (mounting wheel weights to a chromed aluminum lip would tear the chrome up in short order).

2. Even if the entire wheel was chrome plated, it wouldn't make a magnet noticeably stick to them, as I've already established, so it isn't even relevant whether the entire wheel was plated or not (it most certainly wasn't). As further confirmation, I touched a magnet to the stock chromed-aluminum wheels on a 2005 Jeep Liberty today, and the magnet had no attraction whatsoever. Those wheels were also only chromed on the face, and nowhere else. The outer lip where you mount the wheel weights was full of heavy aluminum corrosion/oxidation, dings, dents, and not a shred of peeling chrome anywhere, which would be impossible if that part was plated, but of course, it wasn't, and neither was the rest of the wheel. The chrome-plated face still looked perfect.

The part gets dunked in the copper/nickel/chrome bath during the plating process. How do they only plate 1/2 of the part??     

Plater's tape and/or blocking lacquer (e.g. "Stop-Off"). And they plate far less than half of the part; only the face gets plated, i.e., the main part that you can actually see when the tires are mounted and the wheels are installed.

Say what?

[bill440rt]

Maybe:
A) Ask the manufacturer or dealer what they're made of. Possibly something other than aluminum?
B) Pose the question on a Park Avenue forum.   

[John_Kunkel]

There is absolutely no chrome plating or any other plating of any kind anywhere on the wheel except for the front face.

If the wheel that the magnet sticks too was truly "unplated" anywhere but the faced it would be rusted everywhere else since magnets only stick to ferrous metals (or metals not likely to be found in a wheel) and uncoated ferrous rusts.

[MaximRecoil]

If the wheel that the magnet sticks too was truly "unplated" anywhere but the faced

It is unplated; that's a fact. I wish you or anyone else who is skeptical of this fact lived nearby, so I could win a boatload of money by betting with you.

it would be rusted everywhere else since magnets only stick to ferrous metals (or metals not likely to be found in a wheel) and uncoated ferrous rusts.

No, that's not how it necessarily works. For example, do you know why e.g. 440C "stainless steel" is highly rust-resistant despite the fact that it is primarily composed of iron and a magnet sticks to it strongly? It is because the chromium content of the alloy allows it to quickly form a "passivation layer" of chromium oxide, which seals the outer surface from oxygen and water, both of which are required for rust to form.

Now, aluminum with a relatively small amount of iron impurities, or intentionally alloyed with a small amount of iron (as mentioned in the article I quoted from above) would still be resistant to corrosion for the same reason that any aluminum alloy is, i.e., aluminum also quickly forms a passivation layer (of aluminum oxide) which seals it from oxygen and water.

By the way, there are 3 common metals that are ferromagnetic: iron, nickel, and cobalt. There are some aluminum alloys that contain nickel, but I'd be surprised if they were used for OEM cast aluminum wheels. For example, the R.R.56 alloy contains both nickel (1.3%) and iron (1.4%). I don't know if that would be enough iron and nickel for a magnet to noticeably stick or not.

Either way, I'll reiterate:

Only the face is plated, and even if the whole wheels were plated, it wouldn't make a magnet noticeably stick to them. Magnets don't stick to chrome plating. Even though the nickel layer that is usually present under chrome is ferromagnetic, there is not nearly enough of it to create a noticeable attraction to a refrigerator magnet; you can easily confirm this yourself at home. Nickel isn't nearly as ferromagnetic as iron is, so it takes quite a bit of it before a magnet would noticeably be attracted to it.

[Indygenerallee]

When it all boils down, who gives a crap what they are made of... they are stock Buick park avenue rims....there are bigger mysteries in life to figure out rather than what some "old junk Buick rims" are made of. 

[MaximRecoil]

When it all boils down, who gives a crap what they are made of...

I do, obviously.

they are stock Buick park avenue rims....there are bigger mysteries in life to figure out rather than what some "old junk Buick rims" are made of.  

I don't care what they are; if it was a solid block of what appeared to be aluminum sitting on the floor that a magnet stuck to, I'd be equally curious about what it is made of. Metallurgy interests me, and I couldn't care less whether it interests you or not, but thanks for your third utterly useless reply in this thread all the same.

[73rallye440magnum]

The part gets dunked in the copper/nickel/chrome bath during the plating process. How do they only plate 1/2 of the part??     

Plating thickness is not uniform, and can be manipulated.

[rt green]

well that clears it up. it was right in front of us. lol

[Indygenerallee]

MaximRecoil, is nothing but a  Ive looked into his other worthless posts that he has on here and it looks like he has a position that he has the correct theory on everything.. Worthless to engage in conversation with him..

[73rallye440magnum]

Part location with respect to the cathode in the bath will determine plating thickness.

You can immerse the entire part in the bath and not plate all of it if desired. I'm not suggesting that's how these wheels were manufactured, but there seemed to be some discussion about the subject.

[MaximRecoil]

MaximRecoil, is nothing but a  Ive looked into his other worthless posts that he has on here and it looks like he has a position that he has the correct theory on everything.. Worthless to engage in conversation with him..

^^^ Comical irony, coming from the person who has now posted 4 completely irrelevant (i.e., "worthless") posts in this thread, and is currently "stirring the pot" (), a process which he started in his 3rd useless post, after flirting with it in his 1st useless post.

Your theory was wrong, period. Anyone can demonstrate to themselves at home that a refrigerator magnet doesn't stick to chrome plating. Your claim that the wheels are fully chrome plated is also wrong (not that it matters, because a magnet obviously doesn't stick to chrome plating anyway), as anyone with access to such a wheel can verify for themselves. So out comes the bluster when you're made aware of the fact that you're wrong, which of course is your issue, not mine.

[Indygenerallee]

  Your hilarious Maximrecoil... Mr. internet know it all!!   

[JB400]

Your hilarious Maximrecoil... Mr. internet know it all!!    

I'm surprised it took this long to derail.



You'd have to cut a slice of metal off your wheel and run it through a  mass spectrometer to really determine exactly what your wheel is made of.  Otherwise, your guess is as good as mine, but I doubt if it's better

[Ghoste]

I thought it was just about right on cue.   

[Chad L. Magee]

Your hilarious Maximrecoil... Mr. internet know it all!!    

I'm surprised it took this long to derail.



You'd have to cut a slice of metal off your wheel and run it through a  mass spectrometer to really determine exactly what your wheel is made of.  Otherwise, your guess is as good as mine, but I doubt if it's better

Actually, there is a different way to do this without needing an expensive mass spectometer (it is really overkill for this situation).  First off, I would run a small (less than a gram) sample of this alloy thru a Goey balance to measure the magnetic susceptibility of the material (Xg or Xmole).  Next, I would use acid analysis in combination with benchtop qualitiative analysis on the sample to determine the metals present in the alloy.  By comparing the two tests vs. a set of metal standards for the Goey balance will tell you not only what is causing the magnitization but also at what amounts....

However, I just thought about how to do find out the metals present in the alloy without disturbing the sample with chemicals.  If you use X-ray Fluorescence (XRF), it can identify specific types of atoms present in the wheel.  The problem is the cost ($50,000 for a handheld device) and the x-ray diffractions that would be coming off of the wheel would potentially hurt you over time without lots of lead shielding.  Before you think I am being weird, this is an instument that is used at large airports for bomb detection tests all the time.....