![]() |
Aluminum to Copper interface
I'm no metallurgist so forgive my ignorance. Most of
us have had the problem of interfacing copper to aluminum. Is there some sort of alloy terminal block that will accomplish that feat? Seems simple enough to create an alloy that gradually transitions from copper to aluminum but what do I know? -- 73, Cecil http://www.w5dxp.com |
Aluminum to Copper interface
On Nov 7, 2:36*pm, Cecil Moore wrote:
I'm no metallurgist so forgive my ignorance. Most of us have had the problem of interfacing copper to aluminum. Is there some sort of alloy terminal block that will accomplish that feat? Seems simple enough to create an alloy that gradually transitions from copper to aluminum but what do I know? -- 73, Cecil *http://www.w5dxp.com Cecil, there are plenty of connectors ( Bronze? ) on the market that accept copper/alluminum combinations. On the other hand I understand that if the joint is free from the atmosphere i.e. a tight interface the problem is not all that bad, G.E proved in court during the 50's that if the connection is tight or embedded an increase in resistance does not occur, I believe that analysis still stands. Co defendants that could not provide a similar defence got hammered because their joints did not provide a virgin interface thus existing corrosion was trapped thus it could grow.to a sizable resistance Art |
Aluminum to Copper interface
I'm no metallurgist so forgive my ignorance. Most of
us have had the problem of interfacing copper to aluminum. Is there some sort of alloy terminal block that will accomplish that feat? Seems simple enough to create an alloy that gradually transitions from copper to aluminum but what do I know? As I understand it, the problem with these connections results from at least two factors: - Different galvanic potential. When these metals are in contact, and there's also an electrolyte present (e.g. moisture plus almost any sort of salt), one of the metals will take on the role of an anode, and will start corroding away. - Different thermal coefficients of expansion... repeated heating and cooling puts mechanical stress on the junction of the two wires and can cause the joint to loosen, which increases the resistance, which increases heating when current flows through the joint, which increases thermal stress... In order to use an alloy intermediary to reduce the problem, you'd need one which is midway between aluminum and copper in both galvanic potential, and thermal coefficient of expansion. I tend to doubt whether using a single, monolithic piece of alloy would eliminate the fundamental problem... it'd just spread it out into two separate junctions with lesser but still-nonzero mechanical and galvanic incompatibilities. A tapered alloy as you suggest may well be possible but I suspect that it'd be expensive to make, and might have other problems. Aluminum can be alloyed with copper, but the resulting alloy might be just what you don't want for electrical junctions... the 2000 (or 2xx.x) aluminum/copper alloys are said to be extremely hard but prone to stress corrosion cracking. The approved methods for joining copper and aluminum seem to involve either using high-pressure crimps which create a cold weld, or special pressure connectors plus an antioxidant paste or cream which blocks out moisture and thus prevents galvanic corrosion. I gather it's possible to solder or braze the two metals together, but I don't know what sort of strength the resulting bond will have. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
Aluminum to Copper interface
Cecil Moore wrote:
I'm no metallurgist so forgive my ignorance. Most of us have had the problem of interfacing copper to aluminum. Is there some sort of alloy terminal block that will accomplish that feat? Seems simple enough to create an alloy that gradually transitions from copper to aluminum but what do I know? The problems are mostly the different thermal coefficients of expansion and surface oxidation of Al. Galvanic corrosion can also be an issue. For more than you probably want to know: http://www.inspect-ny.com/aluminum/aluminum.htm If you are talking about your house wiring, the above link will get you to stuff that addresses the problem. If you are talking about home brew stuff, the general solution is to clean, apply anti-oxide grease, and connect under compression, i.e. something with a tightening screw. -- Jim Pennino Remove .spam.sux to reply. |
Aluminum to Copper interface
"Cecil Moore" wrote in message ... I'm no metallurgist so forgive my ignorance. Most of us have had the problem of interfacing copper to aluminum. Is there some sort of alloy terminal block that will accomplish that feat? Seems simple enough to create an alloy that gradually transitions from copper to aluminum but what do I know? -- 73, Cecil http://www.w5dxp.com Hello Cecil, This is the kind of stuff you need. http://www.niled.fr/Gamme_Niled/PDF/B/PageB06.pdf You can also connect directly copper and aluminum if you apply (and maintain) a fair amount of Penetrox P8A (Burndy) all over the joint. Kind regards, Philo |
Aluminum to Copper interface
On Nov 7, 4:33*pm, (Dave Platt) wrote:
I'm no metallurgist so forgive my ignorance. Most of us have had the problem of interfacing copper to aluminum. Is there some sort of alloy terminal block that will accomplish that feat? Seems simple enough to create an alloy that gradually transitions from copper to aluminum but what do I know? As I understand it, the problem with these connections results from at least two factors: - *Different galvanic potential. *When these metals are in contact, * *and there's also an electrolyte present (e.g. moisture plus almost * *any sort of salt), one of the metals will take on the role of an * *anode, and will start corroding away. - *Different thermal coefficients of expansion... repeated heating and * *cooling puts mechanical stress on the junction of the two wires and * *can cause the joint to loosen, which increases the resistance, * *which increases heating when current flows through the joint, which * *increases thermal stress... In order to use an alloy intermediary to reduce the problem, you'd need one which is midway between aluminum and copper in both galvanic potential, and thermal coefficient of expansion. *I tend to doubt whether using a single, monolithic piece of alloy would eliminate the fundamental problem... it'd just spread it out into two separate junctions with lesser but still-nonzero mechanical and galvanic incompatibilities. A tapered alloy as you suggest may well be possible but I suspect that it'd be expensive to make, and might have other problems. *Aluminum can be alloyed with copper, but the resulting alloy might be just what you don't want for electrical junctions... the 2000 (or 2xx.x) aluminum/copper alloys are said to be extremely hard but prone to stress corrosion cracking. The approved methods for joining copper and aluminum seem to involve either using high-pressure crimps which create a cold weld, or special pressure connectors plus an antioxidant paste or cream which blocks out moisture and thus prevents galvanic corrosion. I gather it's possible to solder or braze the two metals together, but I don't know what sort of strength the resulting bond will have. -- Dave Platt * * * * * * * * * * * * * * * * * AE6EO Friends of Jade Warrior home page: *http://www.radagast.org/jade-warrior * I do _not_ wish to receive unsolicited commercial email, and I will * * *boycott any company which has the gall to send me such ads! Sound like David that the rules have been changed and aluminum wiring has now been banned because of the things you say are inevitable for failure! I was unaware that things had got to that point. Has aluminum been baned for all electrical parts in Industry now,? I have been out of touch since retiring but I would have thought that a common connection was a common heat sink which would alleviate some of the things you point to. In the court case I refered to it was accepted that if one material was imbedded into the other such that there was a virgin interface ther was no problem. With respect to house wiring I would not have faith in the workman ship Art |
Aluminum to Copper interface
"Cecil Moore" wrote in message ... I'm no metallurgist so forgive my ignorance. Most of us have had the problem of interfacing copper to aluminum. Is there some sort of alloy terminal block that will accomplish that feat? Seems simple enough to create an alloy that gradually transitions from copper to aluminum but what do I know? -- 73, Cecil http://www.w5dxp.com As others have mentioned, there are two issues involved: differing coefficients of thermal expansion and galvanic corrosion. Placing the joint under strong compression is the method of choice for eliminating the thermal expansion problem. Galvanic corrosion is not so simple to solve, however. Galvanic corrosion, often misnamed "electrolysis", occurs when two (or more) dissimilar metals are brought into electrical contact in the presence of water. When the junction, known as a galvanic couple, forms, one of the metals in the couple becomes the anode (which corrodes faster than it would if the other metal was not present), while the other becomes the cathode (which corrodes slower than it would without the other metal being present). When contact between the dissimilar metals is made, the anode will corrode faster while the corrosion of the cathode will decelerate or even stop. If the terms anode and cathode sound familiar to terms used to describe the electrodes in batteries, they are one and the same. A battery is nothing more than two dissimilar electrodes immersed in a chemically conductive solution. If an external circuit is connected to the anode and cathode of a battery, when the circuit draws current, the anode corrodes. The battery is depleted when the anode is fully corroded away. We can use a galvanic series of metals to predict which metal will preferentially corrode with respect to the other. Usually presented in a table, the metals are listed in order of most corroded to least corroded. I am including one such table with this post, courtesy of the McNally Institute, 1637 Sand Key Estates Ct., Clearwater, Fl 33767. Note that aluminum is located near the top of the table while copper is near the center. This shows that the aluminum is anodic and will preferentially corrode with respect to copper. There are two major factors that increase the degree of corrosion in any dissimilar metal couple: (1) how far apart the two metals are in the galvanic series. and (2) the ratio of the exposed areas of the cathode metal to the exposed area of the anode metal. The further apart the metals are, and the larger the exposed cathode metal area to the exposed anode area, the faster the anode will corrode. An aluminum rivet in a copper sheet will quickly corrode away, while a copper rivet in an aluminum sheet will show far less corrosion (the corroded aluminum is spread out over a larger area). One method of corrosion protection is to use metals close to each other in the galvanic series. The other method is to protect the junction between the metals from moisture. One reader suggested the use of a grease such as Penetrox or Noalox. These compounds, which are carried by most electrical supply houses, are merely fine, irregular-shaped zinc particles in a water resistant grease. When used between aluminum and copper joints, the zinc particles pierce the oxide coatings of both the copper and the aluminum when the joint is placed in compression. The grease keeps moisture out and zinc is very compatible with aluminum; however, the grease and zinc particles do not provide galvanic corrosion protection. These greases are best used in aluminum to aluminum joints. Coating the copper with lead, tin, or lead/tin solder before the joint is made will also provide some degree of protection as these metals or alloy are located between copper and aluminum in the galvanic series. An alloy terminal block that transitions gradually from one alloy to another sounds like a great idea, but it is virtually impossible to make such an alloy. As an example copper aluminum alloys cannot contain more than a few percent copper before the copper precipitates out. Welding, machining, or placing a high copper aluminum alloy under strain can cause microscopic particles of copper to form in the alloy. Localized corrosion will occur around these particles. As amateur radio operators who encounter aluminum antennas connected to copper feedlines, about the best we can do is use good mechanical contact combined with a protective paint to keep moisture out of a joint. I usually use an acrylic paint as it has superior ultraviolet resistance which is needed if the joint is outdoors. My personal favorite is clear Krylon spray for this use. It lets you seen the joint and any corrosion that is formed. Some joints have held up for more than 15 years in my experience. 73, Barry WA4VZQ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~ GALVANIC SERIES OF METALS AND ALLOYS ----------------------------------------------------------- CORRODED END ( ANODIC OR LEAST NOBLE) MAGNESIUM MAGNESIUM ALLOYS ZINC ALUMINUM 5052, 3004, 3003, 1100, 6053 CADMIUM ALUMINUM 2117, 2017, 2024 MILD STEEL (1018), WROUGHT IRON CAST IRON, LOW ALLOY HIGH STRENGTH STEEL CHROME IRON (ACTIVE) STAINLESS STEEL, 430 SERIES (ACTIVE) 302, 303, 321, 347, 410,416, STAINLESS STEEL (ACTIVE) NI - RESIST 316, 317, STAINLESS STEEL (ACTIVE) CARPENTER 20CB-3 STAINLESS (ACTIVE) ALUMINUM BRONZE (CA 687) HASTELLOY C (ACTIVE) INCONEL 625 (ACTIVE) TITANIUM (ACTIVE) LEAD - TIN SOLDERS LEAD TIN INCONEL 600 (ACTIVE) NICKEL (ACTIVE) 60 NI-15 CR (ACTIVE) 80 NI-20 CR (ACTIVE) HASTELLOY B (ACTIVE) BRASSES COPPER (CA102) MANGANESE BRONZE (CA 675), TIN BRONZE (CA903, 905) SILICONE BRONZE NICKEL SILVER COPPER - NICKEL ALLOY 90-10 COPPER - NICKEL ALLOY 80-20 430 STAINLESS STEEL NICKEL, ALUMINUM, BRONZE (CA 630, 632) MONEL 400, K500 SILVER SOLDER NICKEL (PASSIVE) 60 NI- 15 CR (PASSIVE) INCONEL 600 (PASSIVE) 80 NI- 20 CR (PASSIVE) CHROME IRON (PASSIVE) 302, 303, 304, 321, 347, STAINLESS STEEL (PASSIVE) 316, 317, STAINLESS STEEL (PASSIVE) CARPENTER 20 CB-3 STAINLESS (PASSIVE), INCOLOY 825NICKEL - MOLYBDEUM - CHROMIUM - IRON ALLOY (PASSIVE) SILVER TITANIUM (PASS.) HASTELLOY C & C276 (PASSIVE), INCONEL 625(PASS.) GRAPHITE ZIRCONIUM GOLD PLATINUM PROTECTED END (CATHODIC OR MOST NOBLE) |
Aluminum to Copper interface
"Cecil Moore" wrote in message ... I'm no metallurgist so forgive my ignorance. Most of us have had the problem of interfacing copper to aluminum. Is there some sort of alloy terminal block that will accomplish that feat? Seems simple enough to create an alloy that gradually transitions from copper to aluminum but what do I know? 1. I encountered dissimilar metal parts which had been joined by what was termed "explosive welding" and/or "explosive bonding" both of which terms show up nicely in Google. In my case, the parts were cylindrical sleeves, the top of each being stainless steel and the bottom being aluminum. I only saw one (out of thousands) with the bond fractured and I don't know what hit it to break it. They seem quite strong. Perhaps a vendor of such products has something you can use. 2. I see a lot of brass and darn little corrosion. Would a transition piece of brass be acceptable? "Sal" |
Aluminum to Copper interface
On Fri, 07 Nov 2008 14:36:58 -0600, Cecil Moore
wrote: I'm no metallurgist so forgive my ignorance. Most of us have had the problem of interfacing copper to aluminum. Is there some sort of alloy terminal block that will accomplish that feat? Seems simple enough to create an alloy that gradually transitions from copper to aluminum but what do I know? Methinks this might be worth reading: http://yarchive.net/electr/galvanic_corrosion.html It's a collection of postings about glavanic corrosion with lots of good info. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
Aluminum to Copper interface
----- Original Message -----
From: "Sal M. Onella" Newsgroups: rec.radio.amateur.antenna Sent: Friday, November 07, 2008 11:20 PM Subject: Aluminum to Copper interface "Cecil Moore" wrote in message ... I'm no metallurgist so forgive my ignorance. Most of us have had the problem of interfacing copper to aluminum. Is there some sort of alloy terminal block that will accomplish that feat? Seems simple enough to create an alloy that gradually transitions from copper to aluminum but what do I know? 1. I encountered dissimilar metal parts which had been joined by what was termed "explosive welding" and/or "explosive bonding" both of which terms show up nicely in Google. In my case, the parts were cylindrical sleeves, the top of each being stainless steel and the bottom being aluminum. I only saw one (out of thousands) with the bond fractured and I don't know what hit it to break it. They seem quite strong. Perhaps a vendor of such products has something you can use. 2. I see a lot of brass and darn little corrosion. Would a transition piece of brass be acceptable? "Sal" Red, yellow, and naval brass as well as aluminum bronze alloys are marginally anodic with respect to copper so these alloys would provide minimal corrosion protection. I know it might not be obvious, but steel would make a better intermediate metal. This will make sense if the actual voltages are included in the galvanic series. These voltages are in sea water and with respect to a standard calomel electrode. Zinc -0.98 to -1.03 volts Aluminum -0.70 to -0.90 " Cast Iron -0.60 to -0.72 " Steel -0.60 to -0.70 " Red Brass, Yellow Brass, Naval Bross, Aluminum Bronze -0.30 to -0.40 " Copper -0.28 to -0.36 " 73, Barry WA4VZQ |
Aluminum to Copper interface
Brass?
Buck www.N4PGW.org On Fri, 07 Nov 2008 14:36:58 -0600, Cecil Moore wrote: I'm no metallurgist so forgive my ignorance. Most of us have had the problem of interfacing copper to aluminum. Is there some sort of alloy terminal block that will accomplish that feat? Seems simple enough to create an alloy that gradually transitions from copper to aluminum but what do I know? -- 73 for now Buck, N4PGW www.lumpuckeroo.com "Small - broadband - efficient: pick any two." |
Aluminum to Copper interface
Cecil Moore wrote:
wrote: If you are talking about home brew stuff, the general solution is to clean, apply anti-oxide grease, and connect under compression, i.e. something with a tightening screw. I'm putting my rotatable 20m dipole back up and am, once again, needing to connect ladder-line to aluminum tubing out in the weather. I guess I'll try brass hardware this time. If there isn't already, stuff a short hunk of something solid like a fiberglass rod or wood dowel in the end where you make the connection, put terminals on the wires, use stainless screws with star lock washers under the screw head and between the terminal and tubing and the terminal and nut, anti-oxide grease, overwrap with sealing tape then with regular tape. That's how I connected to the vertical in the middle of my lawn where the sprinklers hit it about a decade ago and there have been no problems. FWIW, I tried brass (because someone gave me a bunch) for this sort of thing and switched to stainless. -- Jim Pennino Remove .spam.sux to reply. |
Aluminum to Copper interface
Red, yellow, and naval brass as well as aluminum bronze alloys are marginally anodic with respect to copper so these alloys would provide minimal corrosion protection. I know it might not be obvious, but steel would make a better intermediate metal. This will make sense if the actual voltages are included in the galvanic series. These voltages are in sea water and with respect to a standard calomel electrode. Zinc -0.98 to -1.03 volts Aluminum -0.70 to -0.90 " Cast Iron -0.60 to -0.72 " Steel -0.60 to -0.70 " Red Brass, Yellow Brass, Naval Bross, Aluminum Bronze -0.30 to -0.40 " Copper -0.28 to -0.36 " 73, Barry WA4VZQ Always use Antenna Grease or equivalent on Aluminum contact points to keep the oxidation and moisture out. Steel is subject to rusting, so Stainless Steel or Galvanized Steel is best for antenna hardware to clamp to the Aluminum, and use tinned Brass or Copper loop-eye terminals soldered to the Copper wire and bolted with Stainless Steel or Galvanized hardware. Stainless should have a little Petroleum Jelly, NoAlox or Antenna Grease to keep threads from seizing. I have used Stainless Steel hose clamps and they work fine for quite a while. Aluminum house wiring has been banned a lot of places and is a bad idea all around. The problem is that the Aluminum is weaker. As it is flexed and heated at the connections, it will migrate out and the connection will get loose and you will have a cascade of oxidation and increased resistance. The recommended answer for that failure (If your house didn't burn) was to use a copper wire pigtail out to a wire-nut connection to the existing Aluminum wire with no-alox in the mix. Obviously, there is a loss of integrity and "how to jam the wire nuts into the box" issues. If you have Aluminum house wiring, you should keep an eye on line drops all through the house and run new wiring for any big draw appliance addition. |
Aluminum to Copper interface
Bart Bailey wrote:
What about stainless hose clamps for more surface contact, and of course a liberal application of anti-oxide paste, maybe even some of that self vulcanizing tape on top of it all to try and obviate WX effects? Been there, done that. Nothing seems to completely solve the problem forever. -- 73, Cecil http://www.w5dxp.com |
Aluminum to Copper interface
"NoSPAM" wrote in message ... ----- Original Message ----- From: "Sal M. Onella" Newsgroups: rec.radio.amateur.antenna Sent: Friday, November 07, 2008 11:20 PM Subject: Aluminum to Copper interface snip 2. I see a lot of brass and darn little corrosion. Would a transition piece of brass be acceptable? "Sal" Red, yellow, and naval brass as well as aluminum bronze alloys are marginally anodic with respect to copper so these alloys would provide minimal corrosion protection. I know it might not be obvious, but steel would make a better intermediate metal. This will make sense if the actual voltages are included in the galvanic series. These voltages are in sea water and with respect to a standard calomel electrode. Zinc -0.98 to -1.03 volts Aluminum -0.70 to -0.90 " Cast Iron -0.60 to -0.72 " Steel -0.60 to -0.70 " Red Brass, Yellow Brass, Naval Bross, Aluminum Bronze -0.30 to -0.40 " Copper -0.28 to -0.36 " I saw those numbers decades ago -- in chem class, I guess. I cited brass only because it seems to resist corrosion well, not because I actually know what I'm talking about. g 73, "Sal" (actually KD6VKW) |
Aluminum to Copper interface
"Sal M. Onella" wrote in message ... I saw those numbers decades ago -- in chem class, I guess. I cited brass only because it seems to resist corrosion well, not because I actually know what I'm talking about. g Hi Sal, As an instrumentation designer who worked mainly in the chemical industry, corrosion abatement and material selection were daily facts of life. On more than one occasion, the company metallurgists saved my rear end. For example, stainless steel can be both cathodic and anodic with respect to itself. While most folks consider stainless a panacea for corrosion problems, it is not. In fact stainless alloys have little resistance to salt water. There are many poor owners of stainless auto exhaust systems that learn this the hard way when streets are salted in the winter to melt ice. Copper, brass, and bronze alloys are used in marine environments because of their anti-biofouling properties (barnacles, coral, mussels, etc.). I try to make my posts educational when I can. Thanks for telling me that you had seen these numbers before. I hope they made a little sense this time. I think if we all were back in school, we might pay more attention this time. I know I would! 73, Barry WA4VZQ |
Aluminum to Copper interface
The answer is a tinned crimp-sleeve or a tinned mechanical sleeve Here's one http://www.rshughes.com/products/054007_13319.html Hope this helps "Cecil Moore" wrote in message ... I'm no metallurgist so forgive my ignorance. Most of us have had the problem of interfacing copper to aluminum. Is there some sort of alloy terminal block that will accomplish that feat? Seems simple enough to create an alloy that gradually transitions from copper to aluminum but what do I know? -- 73, Cecil http://www.w5dxp.com |
Aluminum to Copper interface
Who woulda thunk it - Look at this alum-to-copper twister wire connector
http://www.idealindustries.com/produ...ster_al-cu.jsp Google helped to find it Hope this helps Hal - W4PMJ "Cecil Moore" wrote in message ... I'm no metallurgist so forgive my ignorance. Most of us have had the problem of interfacing copper to aluminum. Is there some sort of alloy terminal block that will accomplish that feat? Seems simple enough to create an alloy that gradually transitions from copper to aluminum but what do I know? -- 73, Cecil http://www.w5dxp.com |
Aluminum to Copper interface
"NoSPAM" wrote in message ... snip I think if we all were back in school, we might pay more attention this time. I know I would! Yup. A smarter man than I said, "We'll only need about five percent of what we learned in college; too bad nobody knows which five precent." |
Aluminum to Copper interface
Hal Rosser wrote:
The answer is a tinned crimp-sleeve or a tinned mechanical sleeve Here's one http://www.rshughes.com/products/054007_13319.html Thanks, Hal. I figured they had to exist. -- 73, Cecil http://www.w5dxp.com |
Aluminum to Copper interface
Howdy,
I've been using electric fence crimp terminals from Dare. They're sold in numerous farm and hardware stores. There's a crimper marketed by Dare for them as well at a very reasonable price. They're actually Nicopress terminals. Look like lead plated copper to me. I've joined wire of various materials with these including, aluminum to galvanized steel, aluminum to copper and copper to galvanized steel. They do a fantastic job. http://www.nicopress.com/F1.htm 73, Grumpy Cecil Moore wrote in : Hal Rosser wrote: The answer is a tinned crimp-sleeve or a tinned mechanical sleeve Here's one http://www.rshughes.com/products/054007_13319.html Thanks, Hal. I figured they had to exist. |
All times are GMT +1. The time now is 12:26 AM. |
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
RadioBanter.com