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The Copper Eats the Aluminum

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Ann R. Thryft
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Blogger
Ocean air and metals don't mix
Ann R. Thryft   9/24/2013 11:30:45 AM
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While I can't offer an explanation for why so many US sockets use the copper-aluminum combination, this reminds me of when I lived about a mile away from the ocean and had many problems with the metals in my apartment. That included the need to upgrade the socket on my favorite reading lamp.

patb2009
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Gold
Re: Ocean air and metals don't mix
patb2009   9/26/2013 2:48:12 AM
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Americans are cheap, and companies squeeze every penny out.

 

 

OLD_CURMUDGEON
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Platinum
Re: Ocean air and metals don't mix
OLD_CURMUDGEON   10/11/2013 8:09:12 AM
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YES!, patb2009, I TOTALLY AGREE!  That's one of the MAIN reasons why Americans (the U.S., in particular) feed & support about ONE HALF the free world, and probably one quarter the "not-so-free" world, INCLUDING our avowed enemies!!!!!!!!

I said "Americans", because like it or not, Canadians & Mexicans ARE also "Americans", since we all reside in countries defined by the continent of North America! 

ADIOS, amigo!

 

JimT@Future-Product-Innovations
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umm, disappointingly, ”YES”.
JimT@Future-Product-Innovations   9/24/2013 11:26:30 PM
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I just bought two very cheap ($12/ea) desk lamps for my workbench from Wal-Mart, and both have aluminum sockets, with aluminum contact, and brass rivets.

Taking a quick check at galvanic corrosion of Aluminum on Brass vs. Copper, I see that Brass and Copper have identical potentials on aluminum, so it appears that the answer to your query is ,,,, umm, disappointingly, "YES".

William K.
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Platinum
Re: umm, disappointingly, ”YES”.
William K.   9/25/2013 3:01:15 PM
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Brass and copper have very similar electrogalvanic potentials because brass is mostly copper. So of course.

Now as for why aluminum gets used so much in sockets, it is a fact that aside from costing a lot less, aluminum is easier to deep draw, and all of the threaded parts are deep drawn. So those are the main reasons aluminum is used. The copper rivets are used because aluminum rivets would fail very soon in that environment, while a copper rivet can hold it's preload tension a lot longer. And there is not a fire hazard of any sort when the connection fails, contrary to some assertions. And I have seen and replaced a lot of those sockets over the past ten years or so. It seems that the quality from China does not match the quality from where they came from before. BUT really poor quality and poor manucaturing processes will always produce poor quality products, which does happen sometimes. 

JimT@Future-Product-Innovations
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Re: umm, disappointingly, ”YES”.
JimT@Future-Product-Innovations   9/26/2013 3:15:37 PM
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Of course, you are right –I suffered a lapse there, thinking for a moment that brass was a natural element.  In my mind, I had set Bronze aside as an Alloy, and that (incorrect thought) left Brass remaining as an element.  Had to go back and look at the Periodic Table and a Bronze/Brass  Alloy sheet I have.  Thanks for the correction.

JimT@Future-Product-Innovations
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Re: umm, disappointingly, ”YES”.
JimT@Future-Product-Innovations   9/26/2013 3:35:24 PM
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Meanwhile on the other topic of 'Draw-capable" alloys, you suggested that Aluminum is easier to deep-draw.  In my experience working with draw dies, two alloys called NickelSilver CDA770 and CDA735 were most often chosen because of their superior malleable stretch during the draw.  (These materials are primarily Cu base, so the name NiAg  is misleading).

I remember once trying an aluminum sheet in an existing die designed for CDA770 (as a cost-saving idea) and the Aluminum test part split open.  Point being, I concluded copper was a better draw stock than aluminum.  Maybe the rolled threads for the light socket base helped provide better 'draw' integrity, in these aluminum sockets.

William K.
User Rank
Platinum
Re: umm, disappointingly, ”YES”.
William K.   9/28/2013 5:40:13 PM
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JIm, my guess is that in the line of really cheap alloys that the aluminum alloy used for light sockets is quite cheap, while the copper that draws nicely costs more. Possibly not much more, but perhaps a penny a pound more. Enough to cause quality to be sacrificed for price.

JimT@Future-Product-Innovations
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Blogger
Re: umm, disappointingly, ”YES”.
JimT@Future-Product-Innovations   10/1/2013 11:10:53 AM
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Wow - Check this out:  A LOT more than a few pennies/pound.  Significant average at about 4x the cost.  Rolling average of Base Metal Pricing (updates every minute) http://www.kitconet.com/webcharts/base_metals.html 

At this moment in time:   Al: $0.80/pound.    Cu: $3.25/pound

William K.
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Platinum
Re: umm, disappointingly, ”YES”.
William K.   10/1/2013 2:49:19 PM
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Jim, thanks for the current information, or at least fairly current. I knew that it all had to do with cost, nothing else drives choices of materials for a lot of stuff today. Probably if poor quality steelm were cheaper they would be made of that.

The very cheapest quality of aluminum for castings is unique in that it develops rust spots, since it includes ireon and steel fragments.

OLD_CURMUDGEON
User Rank
Platinum
Is it OR isn't it?????
OLD_CURMUDGEON   9/25/2013 9:38:04 AM
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I'd be willing to bet that IF you went to an antique store, or to a Salvation Army depot, or some similar outlet which has old lamps for sale, and you inspected a typical screw bulb socket, you'd find that the outer shell was actually made from brass also, but was dull nickel plated for its anti-galling & corroding qualities.... just a hunch......

It's hard to fathom that major electrical device manufacturers, LEVITON, PASS & SEYMOUR, HUBBELL, BRYANT,.... the list is endless..... don't have qualified metallurgists on staff that would understand this physical phenomenon!  And, it's just as hard to fathom that the UL & CSA folks, responsible for approving these devices, haven't voiced their objections to such construction!  Or, that the Insurance companies haven't raised concerns over this situation......  How many homes have to burn down BEFORE action is taken?

I can't believe this was done solely as a cost-saving effort, although we've all seen a lot of pathetic examples in this MADE by MONKEES blog where that seemed to be THE sole reason!

Zippy
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Platinum
Re: Is it OR isn't it?????
Zippy   9/25/2013 9:58:28 AM
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Drive for lower-cost products + lack of customer awareness of hazard = inevitable

Larry M
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Platinum
Re: Is it OR isn't it?????
Larry M   10/10/2013 9:13:47 PM
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Well, everyone is grumbling about the dissimilar metals issue of aluminum sockets with brass rivets. Has no one realized that this results in an aluminum-to-aluminum contact between the socket shell and lamp? Changing to a brass socket shell would provide a very large area of dissimilar contact between the threaded aluminum socket and the threaded aluminum bulb base, likely resulting in seizure. It's dangerous to twist a bulb off its base and more dangerous to remove the base from the socket--ideally with safety goggles and power off using pliers or potato. But how many homeowners will do it with bare hands (lacerated fingertips) and no goggles? On that basis the aluminum socket is safer than a brass one.

Amclaussen
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Platinum
Re: Is it OR isn't it?????
Amclaussen   6/5/2014 9:28:58 AM
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Same case as the stupid propaganda claiming that Aluminum wiring is better than copper! while aluminum wiring cost is lower, both conductivity and corrosion aspects point to copper being the best material by a long shot.  But cheap is the word nowadays. Amclaussen.

gusr19
User Rank
Iron
The UK is different !
gusr19   9/25/2013 9:56:39 AM
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It is noted in the article that Europe uses bayonet sockets, but that was predominantly a UK case.  In my experience on the European mainland most lamps were Edison screw based, like the USA.  I have come across UK style bayonet based lamps on the mainland (France) a long time ago in locations where their use was a theft deterrent !

The UK may not experience the corrosion effects, but it suffers from broken "ears" on the bayonet sockets instead and bulbs that are stuck because of the pressure of the spring loaded baynet connections making large depressions in the soft solder areas that make up the contacts ... Which is often the cause fo the broken ears :-(

A quick check shows that the mainland now has bayonet or pin (GU24/MR16 etc.)  sockets on modern (halogen) lamp fixtures, but obviously the Edison screw type are still dominant !  All because of green regulations.




California has banned the Edison screw base from new fixtures to prevent people from using old style incandescent bulbs, so the GU24 pin connection type is the main one on sale there.  Maybe that will eventually take over in the rest of the USA ? CFLs with that base are available outside California even in some DIY stores here in Illinois, and of course on-line.

Nothing is perfect :-(

 

Amclaussen
User Rank
Platinum
Re: CFL's caveats...
Amclaussen   6/5/2014 12:24:42 PM
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It seems that ignorant politicians are causing more damage that good with their "Eco-illogical" measures, like the banning of incandescent bulbs.  Their favorite "luminous idea" is that CFL's are the panacea. They aren't. CFL's have many drawbacks, they contain sizable quantities of mercury.  Should a CFL break and disperse the mercury inside a room, the decontamination would be very costly and difficult, unless you want people living in that bedroom to be exposed to mercury vapor! Have you seen any warning on the CFL's package, or instructions on how to properly dispose of a broken CFL? They also use many electronic parts that end up in the garbage, and some of them are not very environmental friendly at all.  We all pay for their true price through subsides and government intervention.

Their power factor is a lousy 0.5 or so.  They require to be used in applications that allow them to reach maximum brightness (not for stairs or closets where they will only be lighted for less than a couple of minutes). They are not easily dimmable and require well ventilated enclosures. They are a temporary (and incomplete) alternative to the incandescent bulbs until LED's are available at better prices and reliabilty.  Amclaussen.

Critic
User Rank
Platinum
Dissimilar Metals
Critic   9/25/2013 10:05:11 AM
Corrosion can result when metals that are far apart in the galvanic series are placed in contact with each other.  The amount of corrosion depends on the metals, the environment, and the relative areas of the metals. 

The more anodic metal (in this case, aluminum) is the one that corrodes, so it is desirable to make the area of the anodic metal larger that the area of the more cathodic metal (in this case, brass rivets).  This is done in the case of the lamp sockets. 

The bases of bulbs (lamps) are generally made of aluminum, so screwing an aluminum-based bulb into an aluminum socket doesn't cause a problem.  Screwing an aluminum-based bulb into a brass socket would cause the bulb base to corrode, and the bulb could get stuck in the socket.  The areas of the bulb base and socket are similar, so corrosion would be worse than it is in the case when the anode area is large compared to the cathodes (rivets).

When used in a controlled-humidity environment, such as someone's home, the aluminum sockets last for decades, and they have in my home.  Aluminum lamp sockets (with brass rivets) are not intended for use in damp or corrosive environments.  There are brass sockets (and other outdoor fixtures) available for outdoor use, and these are more expensive.  Some bases of bulbs intended for damp/corrosive environments are made of brass, not aluminum.  It would not be a good idea to screw one of these bulbs into an aluminum socket, because it could ruin the socket fast in a damp environment.

You get what you pay for.  The aluminum sockets were not necessarily poorly designed; they were designed to a consumer price target:  cheap!  If you want sockets, fixtures, and bulbs that will better tolerate damp/corrosive environments, you can get them, but expect to pay more.  Most people don't need to pay the extra money.

Larry M
User Rank
Platinum
Re: Dissimilar Metals
Larry M   9/25/2013 11:49:56 AM
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Exactly.  Billions and billions of these sockets have been sold and failure is very rare (and not very costly nor hazardous). In 40 years of home ownership I have had exactly two of these failures, in an outdoor fixture. I repaired one with a 2-56 machine screw, washer, and nut in place of the rivet and the other by compressing the rivet further with punch and hammer.

Jon Titus blogged the other day about a Woodford valve which failed due to bimetallic corrosion. I've had these on a house built in 1965 and they are still fine. I removed the knob recently to replace the faucet washer and the corrosion was insignificant. Bimetallic corrosion does exist but it is not as common as some would make it out to be.

Tool_maker
User Rank
Platinum
Re: Dissimilar Metals
Tool_maker   9/25/2013 2:46:22 PM
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@LarryM: I agree with you. I have rarely had lamp or socket problems as described. However, I do always look for porcelain housings where the application will be bulb down, as in ceiling fans. I have had plastic housings become so brittle, they fall apart when trying to remove the bulb.

  I have also made it a habit to lube an aluminum base with WD40 before insertion as it makes it easier to remove when they have burned out.

mnewkirk
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Iron
The problem...........
mnewkirk   6/19/2014 9:35:36 AM
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No they're made by folks with integrity supervised by greedy monkeys.........

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