Plating onto Magnesium? Q&A's

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A. Hi, Ken. I don't have personal experience in this, but Atotech's MagENta process for electroless nickel on magnesium has a descriptive name that is very easy to remember, and may be a starting point to learn what is special about magnesium when it comes to EN plating. Other major vendors presumably also offer similar processes. Good luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
1995

A. Eric,

My company does finishing of aluminum & magnesium, including dichromate, and mag anodize among others.

You are right about mag corroding very easy - sometimes parts will corrode in shipment from the mfgr. to us.

We always advise our customers when sending in Mag parts for processing that they should be packed with a light machine oil on the parts & desiccant packages should be used in the packaging to absorb moisture.

David A. Kraft
- Long Island City, New York
1998

A. Good corrosion and protective qualities are the responsibility of the casting maker. Packaging, preservation, and proper process control during melting all contribute to end quality.

Too often in the past, foundries have been their own worst enemy with regards to the prevention of corrosion.

New alloys of high purity corrode slower, since trace elements causing galvanic corrosion are reduced in these alloys. AZ91E is a good choice for prototyping auto parts that will have good corrosion resistance.

Mark A. Vecchiarelli
- Enfield, Connecticut
1998

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1998

A. I have some information on how to process magnesium. Maybe you can help your local platers get the process right. Let me know if you want the information.

What are these parts? Would it be worth it to ship them some distance to a plater who can do the job?

  
Tom Pullizzi
Falls Township, Pennsylvania

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A. Hi, Mike.
I can't guarantee it, but I think you'll have less problems with an alkaline electroless nickel strike between the zincate and the sulfamate nickel than you are having with the alkaline copper plating. Good luck.

Regards,

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

A. Don't forget that chips and shavings are flammable if you are doing any mechanical work on the parts. Magnesium parts must either be zincated or nickel plated, and in either case the zincating or nickel plating must be preceded by rather detailed pickling sequences. Volume 5: Surface Engineering of the ASM Metals Handbook has a great chapter on Magnesium Finishing--at least my ninth edition does.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
1999

A. Electroless nickel plating sounds like it meets most of your needs, Wayne.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
1999

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1999

adv.
Luke Engineering offers a patented hard anodic coating for magnesium, Magoxid-Coat(R) which is significantly more wear and corrosion resistant than other widely commercialized anodic coatings for magnesium. A typical coating thickness is 25 µm (1 mil) with one half penetration and one half build-up. It can stand alone or be used as a paint base. A number of manufacturers of superchargers for drag racing use this hardcoating on their magnesium housings and end plates.

Chris Jurey, Past-President IHAA
Luke Engineering & Mfg. Co. Inc.

Wadsworth, Ohio

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A. The gold coating on the Italian wheel might have been ZrN, used extensively for decorative coatings. It is very corrosion resistant if deposited correctly, i.e., by unbalanced magnetron sputtering. ZrN is also very hard and wear resistant, used extensively on cutting tools.

Jim Treglio - scwineryreview.com
PVD Consultant & Wine Lover - San Diego,
California
1999

A. There are two methods to plate Mg. One method is zincate, cyanide copper plate, than plate with whatever metal. Another method is to activate then Electroless nickel plate, then plate with whatever metal. Both processes use a cleaner and etch step.

George Shahin
Atotech - Rock Hill, South Carolina
2001

A. One cannot plate magnesium out of aqueous solutions. The oxidation potential of the magnesium is too large. Clean magnesium will react slowly with water (mag wheels and mag parts are actually alloyed). You can try a dipping process.

Anthony Xidis
- Minneapolis, Minnesota
2001

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Ed. note: We read it that Chua wishes to plate onto magnesium rather than to electrodeposit magnesium.

A. AZ91D is used as diecast, so that has much micro pin hole during die casting process. The cast is observed as sponge structure by electron microscope. The porous structure is easy attacked by chemical in plating or aquatic phosphate treatment etc.

If you want to prevent the corrosion problems, should get sound structure. You can check by gravity measurement or by microstructure.

In my experience, the rolled sheet or extruded plate are better than diecast. For example, AZ31B or AM20 etc.

Simon KangHyung Kim
- Suwon, Kyungki, South Korea
2003

A. Depending on your finish requirements, there are several options for plating on magnesium. You should also contact your thixomolder directly with your specific requirements.

Jerry English
- Schaumburg, Illinois USA
2002

A. I reviewed some early work in "Finishing of Magnesium"

  
Tom Pullizzi
Falls Township, Pennsylvania
2001

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A. Magnesium has been around a long time, Davin, but with the explosive growth in cell phones and portable electronic devices, interest has certainly been renewed!

Tom Pullizzi put together his excellent "Finishing of Magnesium"; Fred Pearlstein, in his usual fine style, covered anodic coatings for magnesium in "Selection and Application of Inorganic Finishes" in the March 1979 issue of Plating & Surface Finishing, discussing them as both final finishes and bases for paint. He found them to be "considerably more protective" than painted conversion coatings.
Another possibility is electroless nickel plating, mentioned earlier in the thread.
Finally, magnesium can be electroplated with any plateable metal you wish ... although the sequence to get there can be complex :-)

Good luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2001

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A. Try the ASM Surface Engineering Handbook, it has a complete chapter on Magnesium surface treatment.

Good Luck.

S. Y. Yuen
- Hong Kong, China
2001

A. Dow Chemical Co. did much of the early work on finishes for magnesium. Their handbook, "Magnesium Finishing", although old and out of print, is still a coveted bible to many finishers. It covers cleaning, etching, conversion coatings, anodizing, and plating. These Dow coatings are still widely used in industry today even though Dow has exited the business and the handbooks have not been available for many years. Recently, new anodic coatings have been developed for magnesium. These offer improved corrosion and wear resistance over those older coatings at competitive costs.

adv.
Magoxid-Coat®,produced in the United States, by Luke Engineering is one of these coatings.

Chris Jurey, Past-President IHAA
Luke Engineering & Mfg. Co. Inc.

Wadsworth, Ohio

2001

A. Mg alloys can be protected in salt spray environment with pure aluminum coatings. Scribed samples coated with Al have survived ASTM B117 tests of up to 196 hours. This contrasts to less than 20 hours for the standard conversion coating. Still the coating must be completely hermetic, as the galvanic potential between Al and Mg is considerable. Thus the complex shape of a product could be a problem.

Howard Gabel
- Santa Barbara, California, USA
2007

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A. Hi, Casey
If the line includes zincating and an alkaline nickel strike, I think there's a good chance. Best of luck.

Regards,

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

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2003

A. Magnesium can be plated by either using the zincate route or by direct plating. The zincate path uses an alkaline cleaner, followed by a chromic acid dip and another dip in phosphoric acid and fluoride. This is followed by a fluoride loaded zincate bath and Rochelle copper to about 5µm. The magnesium is then plated in electroless nickel.

The direct plating path is an alkaline soak, followed by a dip in 150 g/l CrO3 with a proprietary additive. This is followed by another dip in 15% HF at 25 °C and direct electroless nickel. The direct electroless nickel is a mixture of NiCO3/HF/ citric acid /NH3HF/ sodium hypophosphite/ NH4OH at about 85 °C

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

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Q. Thank you for the answer but I don't want to use HF. HF and NH4HF are very dangerous chemicals.
I'm looking for another methods.

Have a good day!

SE DO JANG [returning]
- ANSAN, EE, KOREA
2003

A. Mr. Crichton is correct. Magnesium is a highly reactive metal and your ordinary cleaning and deoxidizing solutions cannot be used for magnesium. All the job-shop platers that I came in contact with use fluoride base predips, and use special electroless nickel containing fluoride to improve adhesion.

June Kim
fine chemicals - Incheon, Korea
2003

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A. My guess is that the parts that blister have porosity. the smallest pores are often the worse because they entrap the first liquid they see. I suggest you try as the first step Hot, DI water (Higher temperature than any other step in the process) about 30 seconds. Hot water will fill the pores and remain there throughout the processing, we hope.
If the parts have oil, a very light solvent followed by an alcohol rinse and dry. Then Hot DI water, etc. This process works well for castings of most metals.

Don Baudrand
Consultant - Poulsbo, Washington
(Don is co-author of "Plating on Plastics" [on Amazon or AbeBooks affil links]
           and "Plating ABS Plastics" [on Amazon or eBay or AbeBooks affil links])
2005

A. You said same alloy, same customer, different housing, no problem. How about the casting process and practice? Is it a fact that both parts are cast in the same way? Or could it be that one is cast in a permanent metallic mold and the other is sand cast? Or one needs a mold release because it's hard to eject and the other one ejects beautifully? Also, your suspicion of a cutting fluid contamination makes sense if it's not used in the part that gives no problem.

Guillermo Marrufo
Monterrey, NL, Mexico
2005

 Thanks to both of you for your advise. Our QC manager talked to the customer about the molding/machining process and we incorporated a hot DI and alcohol submersion procedure. End result; the parts were accepted. Once again, thanks a lot guys.

Randall Fowler - Fowler Industrial Plating, LLC
Cleveland, Tennessee, USA
2005

A. It is usually not possible to pick the best coating, Rasitilo, without considering the full host of circumstances & conditions. But nickel may as a general rule be more appropriate than platinum because, among other things, platinum is a precious metal more costly than gold, whereas nickel is not a precious metal. Some magnesium cell phone housings have been electroless nickel plated.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006

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A. Whatever you do, it needs the blessing of the customer before you spend money on the fix.
If it is less than 0.003" on the diameter (0.0015" per side), I would choose EN because it is very uniform and would require little or no grinding. For chrome, I would not use less than 0.015 per side as your grinding setup needs to be nearly flawless in alignment to the original grind. Chrome dog bones on the ends and you will have quite a bit of grinding to do. Your grinders must be familiar with grinding chrome or they will use the wrong wheel or take too deep cuts and the chrome will probably peel.

James Watts
- Navarre, Florida
May 1, 2009

A. Depending on the overall geometry of the part, how much metal you need to build-up and what your tolerances are, it might be possible to selectively brush plate that ID, perhaps even do it to size as-plated (no grinding or machining). The process is versatile and permits the deposition of a variety of metals whose chemical and mechanical properties can be selected to match or come closer to those of your base metal.

Guillermo Marrufo
Monterrey, NL, Mexico
May 8, 2009

A. Don't forget that magnesium is not aluminium and only in some physical properties (mechanics, melting point, etc.) are the two metals similar, but their chemistry is quite different. For this reason, performance finishing methods are different. On the market, there are some technologies able to offer 1000 hours, or more, of salt spray resistance (Tagnite, Keronite, Anomag, SweetMag).

Aurel Crisan
- Montreal, Quebec
May 26, 2011

A. Hi Chris. Years ago Atotech offered their MagENta process. They might still, or their competitors might offer one. You're doing nickel boron rather than nickel phosphorous, but still the SDS or tech data sheet might offer a hint.

Other than that, we appended your question to a thread where Trevor Crichton seems to offer an authoritative answer to prepping the magnesium, but it does require fluoride. Good luck.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
January 2019

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November 2019

A. Hi Neil. I'm certainly not going to tell you it can't be done; it cam. But it is very difficult from at least four different perspectives which might discourage a nobbyist:

first, it requires dangerous chromic acid and fluorides in the pretreatment cycle;

second, magnesium is such an active metal that you can't directly electroplate it, but must do an immersion plating of zincate on it first;
third, you can't plate acid copper onto the zinc because they are incompatible -- you must either use dangerous copper cyanide, or add the complexity of electroless nickel plating between the zincate and your copper;
fourth, the plating must be thick and pore-free or the magnesium will rapidly corrode because copper is so much more noble.

If you want to proceed anyway, you might get to a technical library for a copy of ASM Metals Handbook Volume 5, which has a 22-page chapter describing the difficulties and the solutions. Best of luck.

Regards,

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