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ted_yosem
Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
finishing.com -- The Home Page of the Finishing Industry

  The authoritative public forum
  for Metal Finishing 1989-2024
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  -----

Restoring Real Mag Wheels by Painting, Plating, Chromating or Clearcoating

none
adv.
this text gets replaced with bannerText
spacer gets replaced with bannerImages

QUICKSTART:

When people speak of "mag wheels" they often mean aluminum alloy. If that is your interest, please search the site using the term "aluminum alloy wheels" plus "strip", "chrome", "powder coating", or whatever.

This thread is about *REAL* magnesium alloy wheels. Early cast wheels were magnesium but went dull quickly, so aluminum alloy wheels overtook them except for racing applications.

In order to build a comprehensive discussion, we merged many threads from 1996 to present -- so please forgive some repetition, a few previously answered questions seemingly re-asked, and items out of chronological order.

We've tried to put descriptive headings in red on sub-topics to make it easier to jump to what you wish to read.

Mag wheel quickly go grey

Q. I have a set of real magnesium wheels produced by a company called Halibrand. When they are polished they look better than chrome/aluminum.

The problem I am experiencing is that "you just have to look at them" and they start to fade and oxidize. At first it was fun using metal polish to return them to their lustrous state but that soon wore off. I subsequently got into a business selling buffs and compounds as I found these worked faster albeit the wheels had to be removed from the car.

My question: Is there some kind of clear-coating process that will withstand the elements but not "dull the shine" of the wheels? Lacquer does not stand up. I have a friend who has a powder coating company so if heat was involved I have access to that technology. The clears he normally uses he is afraid of applying as they tend to dull aluminum and would be hard to remove if a successful shine were not achieved.

Any help would be appreciated. Thanks. - Bert

Bert B [last name deleted for privacy by Editor]
1996


"Engineer To Win"
(Motorbooks Workshop)
engineer_to_win
on AbeBooks

or eBay or

Amazon

(affil links)

A. Real magnesium wheels are no longer produced in great numbers for the reason stated. Most mag wheels still in existence are on early street rods or nostalgia race cars seeing limited use. They have always been a high maintenance item with most early race teams letting the wheels return to their natural dark grey state after giving up on the tedious polishing.

A two-component urethane coating would likely hold up fairly well with a reasonably good appearance; however, I have leaned toward the use of a good quality lacquer for several reasons. While this coating will not hold up as long, it will look much better at thin films, can be easily waxed with auto wax, and ultimately can be easily stripped off with lacquer thinner this on eBay or Amazon [affil links] Warning! highly flammable! when the time comes for the inevitable re restoration several years later. A final thought is to be very careful when power buffing magnesium. Very few shops are set up properly to avoid the potential fire hazards when magnesium dust is present. Good luck!

Bob Anderson
Corporate Marketing Manager - Indiana




Painting / plating magnesium Porsche valve covers & intakes

RFQ: A number of Porsche 928 owners are having trouble with the paint flaking off our magnesium alloy intake manifold and valve covers.

Can anyone recommend someone to re-paint these or plate them with something that will not flake off and take the engine heat.

We currently have 3 people in the process of trying to get this done.

Any help or advice would be appreciated.

Thanks-

Paul Scott
Porsche Owners
1998


Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)


RFQ: The above question concerning the cleaning and painting of Porsche 928 valve covers is the exact question I am facing. I need the same answers. If anyone has the answer, or a link to the answer, I would appreciate it. Thanks in advance.

Dick Mason
- San Jose, California
2000


Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)


RFQ: Same problem but for aircraft wheels.

Mike Leslie
- Mackay Qld, Australia
2001

Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)


A. Your flaking paint is most likely caused by improper cleaning of the magnesium prior to paint. Most painters that prep aluminum use the same low alkaline wash for Magnesium alloys. Magnesium alloys (with the exception of ZK60A) are not attacked by strong alkalies. After a warm water rinse, use a phosphate solution that will inhibit corrosion and improve the adhesion and durability of the finished surface. Use a warm water rinse and then chromate or dichromate the surface depending on the application. The chromate can etch machine surfaces to 60 rms or more but does create an excellent surface prep for paint.

Rick [last name deleted for privacy by Editor]
- East Greenwich, Rhode Island
2003

Ed. note: This forum was built as a gathering place to share camaraderie with tips, pics, anecdotes, & opinions.
                When discussion is requested by strangers who withhold their names, readers may be less likely to engage.


Self-Etching Primer
self_etching_primer_gallon
on eBay or

Amazon

(affil links)

A. I am a paint manufacturer of over 20 years. Use a good Etching Primer. Use a finishing coat that will resist the range of chemicals in which the painted surfaces are likely to get in contact with. The success rate is 99%

Alvin Low
- Singapore
2005


? Are you talking about magnesium parts that are die cast or thixomolded? We've had issues with thixomolding and have resorted to a prime coat of Tagnite to improve paint adhesion.

bob bruffey
- lawrenceville, georgia usa
January 7, 2011




Chromating of magnesium racing wheels

Q. Hi

I need to chromate some magnesium racing car wheels but I don't know which chemicals to buy. Can anyone help me?

Thanks

TONY THEOPHANE
RED SAIL DESIGN LIMITED
1999


A. Hi, Tony.

Please look in your yellow pages for "Plating Supplies", or in our Chemicals Directory here for those chemicals. But there is a lot more to chromating a magnesium wheel than dipping it into a vat of chromating solution. Read on and, just below, we will refer to some pages here that we've prepared specifically for chromating and other anti-corrosive treatments for magnesium.

But there is environmental liability for proper disposal of hexavalent chrome and its rinse water as hazardous waste (it made Erin Brockovich a household name). So you might be better off finding a Jobshop to do this project for you. Best of luck!

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


A. We do aluminum & magnesium finishing.

For chromating magnesium we use a product called Iridite #15.

You do not want to do this yourself. You would need all the other chemicals like mag soap, etc.

David A. Kraft
- Long Island City, New York


sidebar

A. What type of magnesium wheels are they? Are they BBS? And why chrome? Chrome on mags sure wouldn't look good.

Johnny nova


Hi, Johnny. This isn't bright and shiny chrome plating, but a corrosion protection treatment called chromate conversion coating.

Regards,

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




Anti-corrosion Treatments for Magnesium Wheels

Q. I would like to know which is the best system for corrosive protection of magnesium die - cast wheels and for the final coating of them. I know the impregnation system with thermosetting methacrylate.

I was browsing to search for information related to: Surface treatment for magnesium (I remember an old publication of W.P. Innes, and I got this address.

Thanking in advance

Leonardo Z [last name deleted for privacy by Editor]
2000


Halibrand Mag Wheels
wheels_mag_halibrand
on eBay

(affil links)

Q. I have some old Halibrand automobile wheels I would like to restore the original Dow 7 finish on. They are cast from AZ 91 alloy. They are in excellent condition with minor corrosion. Please HELP !

P.S. They are for a Cobra car project.

Eddie Wilbanks
- Eads, Tennessee
2001


"Magnesium Finishing"
by Dow Chemical Co.
dow_magnesium
is sometimes available on
AbeBooks,
eBay, or
Amazon

... but if not, you can find libraries which have copies on WorldCat.org

(affil links)

A. Hello Leonardo, hi Eddie --

Please see our quite comprehensive on-line article: "Finishing of Magnesium" by Tom Pullizzi which includes the needed info on the Dow #7 process / dichromating sealer, as well as thread 14207, "Dow #7 / Dichromate treatment".

If possible, also try to find a copy of Dow's "Magnesium Finishing" booklet (avail on eBay, June 2024) ⇨
Good luck.

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




The History of Mag Wheels

Q. Do you know where I can get student info on the history of magnesium wheels?

Kellie Argy
- LA, California
2001


Kellie,

A. A very interesting question! Perhaps pick up a copy of a magazine for performance cars, i.e., Hot Rod magazine. Many ads for magnesium wheels. Many manufacturers of this type. Contact them all.

Another thing would be to search the web with "magnesium wheels", see what turns up. Good luck!

Bill Hemp
tech svc. w/ chemical supplier - Grand Rapids, Michigan


A. I found this question in my ongoing search for a good way to protect my 16 x 13 Halibrand magnesium wheels. I've written some small articles that deal with the history of Halibrand Engineering and American Racing Equipment magnesium racing wheels. While far from being the definitive text on the subject, it's a start, http://roadsters.com/wheels/#Halibrand

Dave Mann
- Portland, Oregon


thumbs up signThanks for the link, Dave -- excellent article!

Regards,

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




Remove Corrosion from Motorcycle Case

Q. Does anyone have an idea on how to remove the corrosion from a magnesium motorcycle case and leave it bright? I am restoring an old BMW and the case halves are sandcast which is rather rough so it is hard to polish and very time consuming. I've used naval jelly on the aluminum which works fine but it won't touch the magnesium -- actually makes it worse. Any suggestions?

Dan Logan
- Portland, Oregon, USA
2002


A. Magnesium is very difficult to keep bright as you'll read above, which is why today's wheels are usually cast aluminum even if still called 'mag wheels'. Despite being difficult to polish, I think Mothers Mag & Aluminum Polish this on eBay or Amazon [affil links] is probably the best approach.
Best of luck.

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




Q. I RECENTLY PURCHASED A DATSUN 280-Z IT HAS A SET OF CROMODORA MAGNESIUM WHEELS. THEY HAVE BEEN PAINTED, WHICH IS FLAKING OFF. WHAT IS THE PROCEDURE TO POLISH THEM SO THEY WILL LOOK NEW AGAIN. IS THERE SOME SPECIAL MATERIAL TO USE ON A BUFFER?

Thank you,

Steve E [last name deleted for privacy by Editor]
- Osceola, Nebraska
2002


Cromodora Magnesium Motorcycle Wheels on eBay (affil link)]

A. Steve,

Quite a few people ask similar questions about aluminum and mag wheels.

Anyhow, I phoned up the local experts in Surrey.

They remove paint with paint remover BUT often use the Aircraft Stripper because often the paints (on good rims) are painted using a 2-component polyurethane paint.

They also shot peen if necessary. Then they apply a 2-component Polyurethane paint over the finished rims. They did it for us on a 7 year old car which showed signs of salt attack. Superb job.

freeman newton portrait
Freeman Newton [dec.]
R.I.P. old friend (It is our sad duty to
advise that Freeman passed away 4/21/12)





Q. Advice on restoring and polishing Mag Wheels?

Hi actually I do not have a bike, but a 73 Plymouth Roadrunner. Mopars are as timeless as a bike! I have some deep dish mag wheels Ansens 15x10 they are very dull and have blemishes scratches, etc. I have read the VERY useful advice from the folks here (some smart ones I might add). I guess the procedure would be about the same but advise on sanding how to wet or dry ? And polishing till the black is gone?

Thanks for the post,

Robert M Foster
- Marshall, Texas
2003




Need "gold" chromate finish on cast magnesium

RFQ: I have a number of automotive related cast magnesium parts (part of a BMW racing motor). These parts include a manifold casing, valve cover, timing cover and oil pan. These parts all had a gold iridescent finish on them (near as I can describe looks like gold cad plating). I have been told that this is either a Dow 1 dichromate "gold" process or Iridite #15. It is important to get these pieces refinished correctly and unfortunately gold paint doesn't quite work. Looking for someone who both knows what the process is and where I can get it done.

21365-1  21365-2

Mark McClelland
- San Carlos, California, USA
2003

Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)





I have real mags that are a nightmare

Q. I own a 1929 Ford roadster that has American Racing turbo thrust 5-spoke wheels that are real mag. These have been on the car since the late 50's and a real polish problem that takes hours to clean/polish. My son-in-law said I need to have them pickled. Is this something I can do, if so what is required? ANY HELP WOULD MAKE MY DAY. Thank you.

Gary Willey
- Tigard, Oregon, USA
2004


Microcrystalline
Museum Waxes

museum_wax
on eBay or

Amazon

(affil links)

A. The problem is that magnesium is highly reactive and acid dipping (pickling) will not make it less so. You could clearcoat or lacquer the wheels, and it would help but not be a permanent solution unfortunately -- but if you can have a proper chromate pretreatment done first it might work.

Waxing is not totally labor-free but is a lot easier than mechanical polishing, so I think frequent hand application of museum wax ⇨
would make for less frequent polishing.

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




Need a shop to service my mag wheels

RFQ: Need to know of a local shop in northwest Indiana or southwest Michigan that can polish and chrome a set of Harley stock mag wheels.

Sam Reihl
hobbyist - South Bend, Indiana, USA
2004

Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)


Halibrand Mag Wheels
wheels_mag_halibrand
on eBay

(affil links)

RFQ: I also have a pair of Halibrand magnesium 12-spoke spindle-mount wheels in need of corrosion protection. Is there a company that will, at some reasonable cost, apply a protective coating for the individual consumer such as myself for such a low-volume application?
Coating should maintain the color close to the natural color.
Thanks - Lonnie

Lonnie C [last name deleted for privacy by Editor]
- Great Falls, South Carolina
2006

Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)




Q. I am looking for the specifics of restoring various race car parts. I need to know the cleaning process for the magnesium, as well as the dichromating sealer to go on the cleaned magnesium. Any help greatly appreciated.

Thanks,

Vaughn Bright
plating shop - Virden, Illinois, USA
2006

Ed. note: We appended your question to this thread, Vaughn, where it's already answered. But if anything is unclear, feel free to follow up :-)



Dietz number for magnesium make up of wheels

Q. I am taking a welding class and this is all a precursor to finishing and painting wheels. Most aluminum alloy wheels are made up of magnesium - what is the Dietz number or specific type of magnesium?

Brett Kevin Brand
- Philadelphia, Pennsylvania USA
2007


A. The vast majority of "mag wheels" are actually aluminum alloy. Most commonly, for North American cars & light trucks, alloy A356 (strontium-modified) cast by the low-pressure die-casting (LPDC) process.
A356: Al 91.1-93.3(wt%), Cu max 0.2, Fe max 0.2, Mg 0.25-0.45, Mn max 0.1, Si 6.5-7.5, Ti max 0.2, Zn max 0.1, Other, each max 0.05, Other, total max 0.15.

Alcoa produces forged wheels of Al 6061-T6 (to my recollection), mostly for heavy trucks.
Al 6061: Al 95.8-98.6(wt.%), Cr 0.04-0.35, Cu 0.15-0.4, Fe max 0.7, Mg 0.8-1.2, Mn max 0.15, Si 0.4-0.8, Ti max 0.15, Zn max 0.25, Other, each max 0.05, Other, total max 0.15.

Magnesium wheels are usually die-cast, probably mostly by the high-pressure die-casting (HPDC) process. Quantities are small in comparison to aluminum. The alloys are given in ASTM B94 and are mostly variants of AM60 & AZ91. E.g.,
AM60A: 5.5-6.5% Al, 0.13% Mn min,0.50% Si max, 0.35% Cu max, 0.22% Zn max, 0.03% Ni max, balance Mg.

AZ91D: 8.3-9.7% Al, 0.15% Mn min, 0.35-1.0% Zn, 0.10% Si max, 0.005% Fe max, 0.030% Cu max, 0.002% Ni max, 0.02% max. other (each), balance Mg.

Also, a UK site mentioned an RZ5 alloy used for wheels in both Formula One and Superbike competitions.
RZ5: Mg 94.05, Zn 5.62, Zr 0.19, Ce 0.10, Nd 0.03 (wt%).

Now, please explain 'Dietz number' and its relevance to magnesium, finishing and welding; I suspect it's not the kerosene lanterns & Wyoming coal mines found by googling.

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.





How to clean and remove oxidation from magnesium intake manifold

I have an intake manifold that is made out of magnesium that is suffering from some corrosion and oxidation blemishes. Does anyone know the best way to clean raw magnesium without discoloring or ruining the finish? I tried to use lemon juice on an inconspicuous area to see if it worked, but it barely did anything. I contacted Orison Aircraft Company and they didn't have any products that would be able to remove the oxidation and pitting in the finish.

It's quite ugly and annoying...I'd love to get it cleaned off before I put it on my car. Here are pictures of it:

magnesium intake manifold, view 1  magnesium intake manifold, view 2  magnesium intake manifold, view 3

Thanks for all your help and suggestions!

Stew Freeman
Car Buff - Wooster, Ohio
December 6, 2009


simultaneous replies

A. You need to find a shop which can do chromic acid pickle and chromate on magnesium. It's not a back yard job.

jeffrey holmes
Jeffrey Holmes, CEF
Spartanburg, South Carolina


A. Try hot (90-100 °C) 25 gm sodium carbonate this on eBay or Amazon] /25 gm trisodium phosphate this on eBay or Amazon [affil links] /1 lit water solution (5-15 minutes immersion).Rinse well with water and then with pure alcohol or acetone this on eBay or Amazon [affil links] Warning! highly Flammable! .
Hope it helps and good luck!

Goran Budija
- Zagreb,Croatia




Q. Hi. I operate a small vintage race motorcycle restoration business I hope you may be able to help, I have a few sets of 1970's era cast magnesium motorcycle wheels which need stripping and refinishing do you have a product for chromating magnesium? If so what colour finish does it leave the casting?

Kind regards

Bruce Rigby
motorcycle restoration business - Brisbane, Queensland, Australia
April 22, 2011

Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)



"Magnesium Finishing"
by Dow Chemical Co.
dow_magnesium
is sometimes available on
AbeBooks,
eBay, or
Amazon

... but if not, you can find libraries which have copies on WorldCat.org

(affil links)

A. Hi, Bruce. We have an article online here that explains the various approaches to magnesium finishing: "Finishing of Magnesium".

Dow's "Magnesium Finishing" handbook is a great reference ⇨
but it is out of print and hard to find.

Good luck.

Regards,

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




Chrome Plating of Mag Wheels

Q. Can real mag wheels be chrome plated? I have a set of 15 inch x 4 inch American Racing magnesium 12 spoke rims.

Real magnesium wheels before plating 0003-1a   Real magnesium wheels after plating 0003-1b  

As anyone knows with these rims, the polishing required to keep them shined is a full time job. Has anyone had success or experience chroming or nickel plating them? Thank you.

wikipedia
Pacers Auto
Scott Snizek
Pacers Auto, Inc ⇨
West Hempstead New York USA
December 20, 2018


A. Yes, magnesium can be chrome plated. It may take some effort to find a shop which does that as the demand must be very small.

I can't say for certain, but the highly reflective wheels in your second photo, I'd wager are highly polished and buffed magnesium and are not chrome plated. They may have a clear lacquer coat to keep them shiny longer.

jeffrey holmes
Jeffrey Holmes, CEF
Spartanburg, South Carolina


Sharkhide
sharkhide_protectant
on eBay or

Amazon

(affil links)

thumbs up sign  Yes the wheels in the second photo were highly polished and would stay like that as long as they were attended to with Mothers Mag & Aluminum Polish this on eBay or Amazon [affil links] or White Diamond metal polish this on eBay or Amazon] .

I also had success with a product called Sharkhide ⇨
which is used as sealant coat for aluminum pontoon boats. But to be fully sealed the wheels would have to be polished, then fully sprayed with Sharkhide so no areas were left exposed. That means the wheels need to be unmounted. The coating acts as a clear sealant and a buffer to the environment. I did a test on a polished magnesium timing plate starting from a gray color and after polishing and sealing, it was left untouched in the environment for a month. It was rained on it plenty of times. The uncoated portion grayed up and the rest remained polished.

Scott Snizek [returning]
Pacers Auto, Inc - West Hempstead, New York USA




Lamborghini Magnesium Wheels

Q. Hello,

I have a Set of Magnesium Wheels. I have repainted them, but after some time the paint become bubbles (I think you know what I mean).

Now I give them to a professional paint stripper; they removed all the paint to bare metal.

I heard that a coating with Alodine 1200 or Bonderite M-CR 1200 is a good base for the following painting, but I am not sure.

Can someone give me help for a good but as easy as possible way to prevent the rims from corrosion and the paint from getting bubbles again?

The problem is I am from Germany and maybe it is tricky to find all chemicals here in Europe?

Markus Goerlich
- Langen, Germany
October 27, 2017


A. Hi Markus. It is true that chromate conversion treatment with hexavalent chrome, like the examples you mentioned, can be a good preparation process, however, chromates specifically tailored for magnesium would be better than what you mentioned which are tailored for aluminum. Due to RoHS and other toxic reduction programs, you may not be able to buy or do such hexavalent chromating these days. Not quite as good, but still worthwhile, might be a trivalent chromate conversion coating such as Alodine 5200 (I don't know for sure, but I suspect there may not be any trivalent chromates designed for magnesium).

Regards,

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


A. Try phosphate finish. According to Russian sources you can use 0,3 gm sodium silicium fluoride/ 30 gm manganese monophosphate/1 lit water solution/ temp. of solution 95-98 °C/15-20 minutes immersion. Hope it helps and good luck

Goran Budija
- Cerovski vrh Croatia


Q. Hello Ted,

Do you mean this:
BONDERITE M-NT 5200 MU AERO
It seems that is only in big packages available

Do you know PreKote?
https://www.aircraftspruce.com/catalog/cspages/prekotesurface.php

Markus

Markus Goerlich
- Germany
October 4, 2022


A. Hi Markus. As you can see on this page, Dow wrote a whole book on the surface treatment of magnesium. Finishing.com's Tom Pullizzi wrote a fairly complete summary of magnesium treatments back in 2000.

But in short, the products you mentioned are fairly similar non-chromated products from two major suppliers, and either should be okay. It is true that it gets harder and harder to get small packages of such products, but you might inquire of a local distributor of such metal finishing products.

Luck & Regards,

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


So I get BONDERITE M-CR 1201 AERO , but I don't get Alumiprep 33, this was suggested from another forum for magnesium rims.

What can I use to remove the corrosion? I removed the old coating with soft stripping, then glass blasting. But do I need something else before I spray on the 1201 Bonderite?

Markus Goerlich
- Germany


A. Hi Markus. Even though you stripped and glass blasted the rims, that was a while ago, and magnesium is a very active metal which oxidizes a bit immediately, but additionally as time goes by. The other forum was apparently suggesting a pretreatment in Alumiprep 33 (now apparently renamed BONDERITE C-IC 33) this on eBay or Amazon [affil links] , which is a phosphoric acid based cleaner/pretreatment for aluminum, perhaps on the basis that the acids in the Bonderite M-CR 1201 (probably formerly called Alodine 1201 this on eBay or Amazon [affil links] ) may not be reliably strong enough to dissolve that oxidation depending on the time elapsed since blasting, etc.

It is difficult to proceed with book learning or internet learning to processing a set of rare magnesium wheels when that metal's traditional finishing steward (Dow Chemical) decided to abandon the field, leaving us with only "magnesium is sort of like aluminum in some ways, so the chemicals designed for aluminum processing will have to be tried", and because the supplier of those chemicals is a multi-billion dollar megacorp uninterested in selling an individual a small quantity nor in their success in treating their rare magnesium wheels with this product designed for aerospace aluminum.

Moreover, it is also generally understood that "your mileage may vary". So at this point I would suggest that you try to chromate treat (Bonderite M-CR 1201) some scrap magnesium of the same grade as your wheels if you have any available; and if not, then bite the bullet and treat ONE of your set of wheels and paint it, then see what you learn from actually doing it. If it looks good, and you can't pull any chips of paint off with duct tape, proceed with the others.

Apologies that perfect instructions are unlikely to be forthcoming in an age where old magnesium wheels get ever rarer, formerly available products are no longer made for environmental reasons, multi-billion dollar megacorps have bought up all the old small suppliers, then dropped support at the drop of a hat. Sorry about what happened to the magnesium finishing industry, but there are still jobshops specializing in finishing of magnesium, and you might want to rely on them rather than doing it yourself.

Luck & Regards,

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




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