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Compatibility of aluminum and brass



Quickstart:
     The best know example of galvanic corrosion is metal boats protected form corrosion by zinc anodes. Zinc is more 'active' than steel or aluminum, so when corrosive conditions exist which would steal electrons from the steel or aluminum, causing them to dissolve into the water, they in turn are able to steal electrons from the zinc, so the anodes corrode instead of the boat.
     But galvanic corrosion is often bad rather than good. The conditions required for it to happen are: dissimilar metals, with one more active than the other; metal-to-metal contact as a pathway for the electrons; a conductive liquid such as salt water.

Q. I was reminded of the incompatibility between brass and the aluminum a couple of days ago when I tried to disconnect a garden hose with aluminum connections on the ends from a sprinkler that has a brass connection and found them galvanized together.

Which material can act as an adapter between brass and aluminum so that neither of those metals will galvanize with it? If memory serves correctly, stainless steel is the answer.

Gary Workman
- Arlington, Texas
May 15, 2025


A. Hi Gary

Yes, stainless steel is more compatible with aluminum and with brass than they are with each other. But galvanic incompatibility is probably not as much of an issue here as the aluminum itself  🙂

Aluminum oxidizes and swells, and it galls (cold welds) terribly even against itself; using teflon tape or thread sealant is probably the best you can do when a hose has aluminum fittings.

I got a new garage door decades ago, at a time when someone had the "bright" idea that the cost of locks could be reduced by using aluminum pins in them. It was also an age when hardware stores were making keys out of aluminum. My wife had a duplicate key made and we didn't read the warning against it. The first time the key was inserted it became instantly, totally, and permanently non-removable.

Luck & Regards,

ted_yosem
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey






⇩ Related postings, oldest first ⇩



Q. Hi my name is Rhonda, I'm in the hardware business and I am trying to find the correct answer for several of my customers as pertaining to small engine repair. The question is this:

If a brass pipe nipple is inserted into an aluminum block engine for the purpose of simplifying oil draining, will there be any galvanic action between the engine block and the brass nipple? Or would it be better to use black iron or galvanized iron?

Thank You.

Rhonda Reeves
hardware store employee - Boston, Massachusetts
2005


A. Brass is incompatible with aluminum, per MIL-STD-889 (and Notices 1, 2 & 3 thereof) DISSIMILAR METALS.
Galvanized is your best choice.

Ken Vlach [deceased]
- Goleta, California
contributor of the year Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.



A. I think an aluminum nipple would be the best choice from the corrosion point of view. You didn't mention it. Why aren't you considering it?

Guillermo Marrufo
Monterrey, NL, Mexico


A. Come on guys. A little application perspective here. It is a small engine nipple covered in oil. How much galvanic corrosion will occur? Surely not measurable in my lifetime. Brass, Black Pipe or Galvanized should be fine. For added protection use some good High Temperature anti-seize on eBay or Amazon [affil links] and you will be fine.

Thomas J. Martin
- New Britain, Connecticut, USA


Thanks, Thomas ... I certainly can't strongly disagree with you, and if a backyard mechanic was working on his own beater, I'd agree a hundred percent.

But Rhonda is trying to educate herself on the issue of galvanic corrosion to be able to best help her customers, and the answers may be helping her do that.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey


A. The fact that this question is even being asked is commendable! I remember the days I always went to the corner, independent hardware store to get advice. Well, all those corner hardware stores are gone - replaced by the mega-importers such as Lowes and Home Depot! If I can't have my independent corner hardware, at least I have a new found respect for True Value! One of the questions here is how much dissimilar metal area is exposed? The fact that the inside is bathed in oil helps the inside (oil is a really poor electrolyte corrosion wise), however, the outer portion of the aluminum and the brass is where the corrosion will likely progress from. Painting or otherwise covering up the dissimilar metal junction is the best bet if you have to go with brass to aluminum. I'm sure True Value carries either an aluminum or cold galvanizing compound ⇦ on eBay or Amazon [affil links] . Cadmium plating is used heavily by the aerospace and military industry to interface between aluminum and either steel or stainless, but I wouldn't' suggest this since the result would be a non-RoHS compliant product!

milt stevenson jr.
Milt Stevenson, Jr.
Syracuse, New York


A. Should be fine. Since the aluminum is relatively much more anodic that the brass, it would normally experience more corrosion. However since the aluminum is so much more massive than the brass in your situation, it acts as a sink, and won't experience any concentrated corrosion. In a nutshell, galvanic corrosion becomes essentially negligible, and neither metal will corrode any faster than they would normally on their own.

Mike G. Maine
- Melbourne, Florida




Q. Have a Pontoon boat with aluminum pontoons; need to put a plug into the pontoons. What should I use for a plug: BRASS? GALVANIZED? OTHER ?

Bryan Carter
- Cropwell, Alabama
May 4, 2013


A. Machine cut them out of Aluminum itself and Anodize them to prevent them corroding tight together. Why think about another material?

Khozem Vahaanwala
Khozem Vahaanwala
Saify Ind
supporting advertiser
Bengaluru, Karnataka, India
saify logo




Q. I am doing a project using various small sizes (1/2" - 7/8") of round tubes that I want to slide rings onto as an architectural detail. The perfect "rings" that I found are brass compression sleeves that are used in compression fittings for copper pipe. I know steel tube is bad, but for this "interior" application would aluminum be acceptable?
When it's done it will be powder coated.

Larry Gautreau
interior glass specialties - San Bernardino California US
July 24, 2014


A. Hi Larry. Almost anything is okay in a climate controlled interior application :-)

Galvanic corrosion requires, in addition to a metal-to-metal contact between dissimilar metals, an "ionic path" (salty moisture).

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey




Q. As a hobby project I wish to thread a brass screw (6x32) through a 1/8 aluminum angle bracket (1x1x1" wide). Since this item will be in a air conditioned house/room, I gather from other messages here that I likely will not experience any negative metal-to-metal reaction. Is that true? Thanks in advance.
Mike

Mike Pilgrim
- Boca Raton, Florida, U.S.A.
July 14, 2016


A. Hi Mike.
Such decisions are based upon both the criticality of the situation and the environment.

Such a joint would probably not be permitted to hold a heavy electronic instrument in place over the captain's head even in the air conditioned flight deck of an airliner because the consequence is life-critical; and it would not be okay for even a dollar-store mud flap for a truck because of the corrosive winter environment. But for a hobby application in an air conditioned room, I'm confident that it will be absolutely fine. Good luck.

Regards,

ted_yosem
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey


thumbs up signTed, thanks for your response and your humor. I'll try to remember not to try this technique next time I tackle a mud flap attachment.

Actually, in the unfortunate event of a major disaster this finished product could come into play as a life-support communication instrument ... My hobby is Ham Radio, and this is going to be my effort to create (cheaply) a Morse Code key which can act as a backup as needed, to a Commercially made device on the market for $536. I'm hoping my rendition will cost less than $10. Thanks again for giving me confidence to use on-hand materials (brass screws and aluminum angle iron).

Mike Pilgrim [returning]
- Boca Raton, Florida, U.S.A.




Can aluminum be brazed to brass?

Q. Hello, I'm David, a neighbor of mine asked for help repairing a decorative brass spoked wheel on a tea cart. The problem is the rim of wheel is aluminum and was friction fitted originally, and now the spoke ends have broken slightly, preventing reassembly in the same fashion. Can aluminum and brass be brazed (it will be in an climate controlled environment)? Thanks.

David Normand
- The villages, Florida USA
July 22, 2020


Muggy Weld
low temperature soldering
muggy_weld
on eBay
or Amazon

(affil link)

A. Hi David. Yes, aluminum and brass can be "brazed" together, but I'll raise outstretched arms overhead with two crook'd fingers in each hand when I say it because the question is probably more semantics than technology :-)

Metallic materials can be melted to hold the brass and aluminum together, but some people might consider some or all of the methods "soldering" rather than "brazing". If you google "braze aluminum and solder" you will see a number of youtube videos as well as links to proprietary meltable soldering/brazing metals. Good luck.

If you run across John & Debbie B. from Kinnelon, NJ in your little village, say hello from their former next-door neighbors the Mooneys.

Luck & Regards,

ted_yosem
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey




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