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Vintage Motorcycle Restoration: Aluminum Anodizing Removal & Repair




Q. Hello. I too have a question regarding 'smut'. I have some 1972 Triumph engine cases that were left to rot in a damp shed for 20 years. They developed what I think is Aluminium oxide ( rust ) , a white powder like substance on parts of them. I thought I read the answer to remove this was Phosphoric acid which is present in Coke-a-cola, so I covered the bad spots with it and left it overnight. I discovered to my horror when wiping off the coke, black 'smut' marks.

So am correct in saying that this is the remaining metal left over within the alloy, that didn't react with the oxygen?

Also, is the only way to clean these parts (de-smut) is by using Nitric Acid which my investigations so far leads me to believe (impossible to get in the UK), or is there any other way to remove them. I can't polish as this part is a rough cast lower case and so the surface is irregular.

I am in the process of making a soda blasting cabinet, but somehow I don't think this will be powerful enough to clean these marks out of the surface, so is this a case for sand blasting? Many Thanks in Advance.

Mike Smith
- Stroud,Glos , Uk
September 1, 2016




⇩ Closely related postings, oldest first ⇩



2002

Q. I cannot believe my luck in finding your web site and forum! I am restoring a vintage motorcycle of extraordinary value. I am not a shop, just a private owner on one heck of a learning curve.

I am currently struggling to figure out how to restore the outside finish on the (4) Japanese aluminum carburetors to the original shine without damaging the castings, ports, fine threads and seats that infest these carbs. None of the motorcycle or auto shops has a clue and tell me I'm wasting my time. They say to just use an aluminum buffing compound and elbow grease -- not an acceptable answer in this situation. I work for a aircraft company so I am familiar with how they restore skins and aluminum components.

I hope there is some sort of dip or applied liquid compound that can deoxidize them. I am doing the restoration in my shop at home, so exotic and dangerous materials cannot be used.

The motorcycle will be used for show display, museum loans, and ... I still occasionally ride it so everything I do has to be considered within these parameters. I have junk carbs to "test" with.

The other question I have is, some of the suspension parts, fork housings and such, have a plastic coating on them that needs to come off without hurting the aluminum. it is worn away in some spots and the aluminum is oxidized . So They need restoring also. How do I get this plastic coating nightmare off the parts?

And lastly. when all these parts need shining up, what is the best way to get a mirror like finish on them?

Wow that's a lot. I appreciate any help you can offer.

With Respect,

Jon B [last name deleted for privacy by Editor]
- Tacoma, Washington



A. Hi, Jon. I don't have hands-on experience with such issues, but will give you some book knowledge until someone who has actually done it comes along.

For plastics, paints and clearcoats -- basically any organic finish -- Aircraft Stripper will remove it with no damage to the aluminum. However, this is methylene chloride based and is very toxic; rubber gloves [on eBay or Amazon], goggles [on eBay or Amazon], excellent outdoor ventilation, and every caution against spillage, splashing, and fume inhalation are mandatory.

For the surfaces which seem to be anodized (hard to scratch and non conductive), you'll want to remove that. In your aircraft company you could use a mix of chromic and phosphoric acid, but in your hobby you would be restricted to an alkali like oven cleaner [on eBay or Amazon]. Unlike the acid, the oven cleaner [on eBay or Amazon] will attack the aluminum substrate as well as the anodized coating, so timing is important. Again, googles, gloves, and care are required. If you do dissolve aluminum, that leaves copper and other alloying materials behind, which appear as a gray-black smut. In an airplane factory this is removed with a "desmut" step, but you won't be able to easily remove it with household products . . . I suppose you can try a mixture of vinegar [in bulk on eBay or Amazon] and salt on your scrap parts; but don't overdo the Easy-off in the first place and you won't get smut.

At some point you do have to do mechanical finishing; you can't do it all chemically. Buffing is the easiest approach, although I suppose you could try a hobby rock tumbler [affil links] since you have spares to play with.

When you're done polishing, you need to clearcoat it. There are many approaches from simple one-component liquids you "paint" on, like Everbrite [a finishing.com supporting advertiser], which is fine but needs to be redone periodically, to 2-component spray-on automotive clearcoats. Good luck.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2002


A. I did this on my Virago engine sides last year as the plastic coating had become loose and tarnished. I tried various things, but finally stumbled on paint remover [on eBay or Amazon] . It safely removes the plastic film and does not damage the aluminum. I then followed up with standard aluminum polish, and in the last year no problems have surfaced.

Herman [last name deleted for privacy by Editor]
- St. Marys, Ontario, Canada
2002



Q. For Herman in St. Mary's, Ontario, Canada ... what kind and/or brand of paint remover did you use?

Terry Syropoulos
- Oakville, Ontario
2007



probertEthumb Aluminum How-To
"Chromating - Anodizing - Hardcoating"
by Robert Probert

You'll love this book. Finishing.com has sold 880 copies over the years without ever a single return request :-)



A. Thanks Herman.

Hi Terry. People come and go on a public forum, so I don't know if Herman stops by anymore. But it must be the nasty and noxious methylene chloride based paint remover, not caustic based paint remover, to be confident that it will not attack the aluminum. That's why I prefer to look for Aircraft Stripper, which is simply paint remover, but it's labeled so you know it's the type that's okay for aluminum, not the caustic kind.

Regards,

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




Q. Hello
I had my old honda clutch+alternator covers glass beaded. What kind of compound or polish or process is best to get rid of the dull grey and bring back the factory polished or brushed aluminum finish.

Thanks
John

John Donahue
- Worcester Massachusetts USA
December 6, 2010



"How to Restore
Metal Auto Trim"

by Jeff Lilly

on AbeBooks

or eBay or

Amazon

(affil links)

A. Hi, John.

The usual result of glass bead blasting is a matte surface; in fact it's often done for exactly that purpose, so I'm curious why you would specify a finish that delivers the opposite of what you want :-)

Buffing or polishing back from a matte surface to full bright will probably take more than one polishing step. Letter 800 offers pretty exhaustive coverage of polishing aluminum. Good luck.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
December 6, 2010


A. I recently had the need to have a pair of '58 Zenith carbs, and mechanical fuel pump restored for an old BMW I'm doing. They are die cast; not aluminum and were they ugly; dark gray and stained. After glass bead blasting they were put in a vibratory tumbler with filled with ceramic media and water. After about an hour they look as good or perhaps better than the day they were made. The finish is smooth and clean, no blasting evidence. I have to think this would work excellent with aluminium parts.

Stuart Erskine
- Pasadena, California
2007



Q. Hi, I cannot get Easy-off oven cleaner here in Ireland. I want to polish the chassis of my 98 CBR 900 Fireblade. It there anything that you can suggest to remove the Anodizing or should I just sand it off.

Declan Nixon
- Galway, Ireland
July 10, 2008


A. Hi, Declan. caustic soda [affil links] (sodium hydroxide) strips anodizing. Easy-off is just one commercially available form of it. Alkaline drain cleaning products, diluted, can be used as well. All of these materials are, however, dangerous and extremely caustic to human flesh. Don't go near any of them without goggles.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 11, 2008



Q. There are some more questions I need to ask. How dilute should the caustic soda be. How long should I leave it on the chassis. How should I apply it to the chassis?

Declan Nixon [returning]
- Galway, Ireland
July 13, 2008



A. Hi. Note that caustic also dissolves raw aluminum, not just the anodizing. I don't think untrained hobbyists should be trying to strip anodizing with toxic chemicals. So some some hands-on instruction by someone who has done it, and some practice with scrap parts before committing real parts to it, would be a very good idea; please don't use precious parts for trial and error learning. Good luck.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 15, 2008


A. Since this is an in-place strip, I would use a paste made of bicarbonate of soda and the finest scotchbrite pad sold with lots of rubbing. Calcium carbonate from a swimming pool place is a bit stronger. Both are slow but are far more safe than lye. If you must use lye, start out with a heaping tablespoon in 1 gal of warm water. Again, a very fine scotchbrite pad.

James Watts
- Navarre, Florida
July 15, 2008




Q. I AM IN THE PROCESS OF RESTORING A 1977 HONDA XL 125 AND NEED TO REMOVE THE OXIDATION OFF THE ENGINE AND OTHER ALUMINUM COMPONENTS. WHAT CAN I USE THAT WILL RESTORE THE PARTS TO ORIGINAL LUSTER?

Jerry P [last name deleted for privacy by Editor]
- Wellborn, Florida
 




A. Hi Jerry. We attached your question to a similar posting where it was already answered. But you won't get to full brightness chemically. You'll need to do some buffing.

Regards,

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



Q. What would you suggest to restore cylinders, between fins?

Ed Jorgensen
- Aldan, Pennsylvania USA
September 1, 2012



A. There is a company in California that uses water and baking soda to blast the aluminum. It comes back looking absolutely AMAZING! Like it was brand new. I saw a clip on a television show where someone sent parts for restoration and the end result was the best I have ever seen. It removes every speck of grease, grime and oxidation. I am beginning the restoration of a 1965 Ducati 250 and will be sending them my engine case, cylinder, head and carb for this service. I don't remember the name of the company but Google should point you in the right direction. Good luck and happy restoring!
Tom

Thomas Crawford
- Chicago, Illinois, USA
January 1, 2013




Stripping anodize from Yamaha R1 before polishing

Q. I am getting ready to POLISH the frame on my 1998 Yamaha R1 and I was wondering what is the easiest method of removing the clear coat / anodized silver coating over the aluminum? I tried a small area and sandpaper seems like such a task. I was told or actually heard that OVEN CLEANER is a way to remove the coating over the aluminum?

Thanks in advance,

Matthew Silva
- East Prov, Rhode Island, USA


A. If it is anodized, the best stripping medium is chromic-phosphoric acid, but only an anodizing shop would have that. The problem with oven cleaner or any other caustic solution is that it attacks not just the anodized film, but the aluminum as well, so timing is important. You may be able to strip the anodizing yourself with oven cleaner, but I probably wouldn't :-)

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



Q. I have also been told that Oven Cleaner will "do the job" in the absence of a commercial product. I understand your concerns but am wondering what sort of damage caustic solutions can cause to aluminium and how quickly this can occur. What sort of problems are you specifically warning against?

I suppose from the point of view of a "do-it-yourselfer" I would like to know what readily available substance would remove this coating as safely as is possible.

Obviously after removal of the anodising the surface would be prepared prior to buffing (Wet & Dry.) Would this help to remove any damage caused?

Aaron Hunt
- Perth, Western Australia, Australia
 



A. Hi Aaron. Any caustic solution like oven cleaner attacks raw aluminum almost as readily as it attacks the anodized film. Yes, it is possible to remove an anodized film with caustic & careful timing, and some commercial shops operate with caustic as their anodizing stripper rather than using chromic-phosphoric strippers. But if left on too long, it's busy eating the aluminum. There is actually no "limit" to how much it can attack aluminum. In fact, a common metal finishing process to make complex hollow parts is to machine a solid mandrel/mold out of aluminum, electroplate it, and completely dissolve the aluminum mandrel away in caustic, leaving the plating as the object.

"Safely" is a problematic term; oven cleaner is fairly nasty stuff. Don't forget the goggles! But in industry, and even wearing full protective gear, no shop would let you near the stuff until you had passed a haz-mat training course; so when you ask what a consumer has to do to work with it "safely", you can see the problem.

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



Q. I saw Aircraft Stripper. It claims it won't damage or stain the aluminum. However it probably works good for paint, but is it strong enough to remove the anodise coating?

Marty Leblanc
- Dieppe, New-Brunswick, Canada
 



A. Aircraft stripper will pull off a lot but it seems to be very patchy. I'm finding this out right now. I still end up sanding A LOT!

James Nebel
- Fairbanks, Alaska
 




Hi, Aircraft Stripper is methylene chloride, which is a strong solvent, but still a solvent. So it removes clear coats and other organic finishes quite readily, but it's not the thing to use to remove anodized coatings. For that, chromic-phosphoric acid is best, as previously mentioned, and oven cleaner is probably second best.

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




Multiple threads were merged: please forgive repetition, chronology errors, or disrespect towards other postings [they weren't on the same page] :-)



thumbs down signI made the mistake of using the local car wash on my 08 sportster and it tarnished/etched all of my aluminum parts on the bike. It sucks. Stay away from the car washes and their recycled water. The only thing that cuts it better is a product called Mr. Buffer -- it seems better than most.

Dave Jeffus
- Wasilla, Alaska
December 18, 2008




Harley V-Rod swingarm damaged by oven cleaner

Q. I recently bought a Harley Davidson V-Rod with an aluminum body. I got some plastic stuck to my hot pipes during a ride and used a small bit of Easy-Off Oven Cleaner and razor to successfully remove it. In the process I accidentally sprayed a few droplets on the aluminum swingarm and put some "whitish" dots on the finish that will not come off. I was wondering if there is a product or process to remove them without disrupting the surrounding finish too much.

Thanks,

Anthony Martinez
Student/Teacher - Los Angeles, California, United States
2003


A. You really should not have done that. The oven cleaner would not damage chrome or steel, but the aluminum is damaged (not stained). Perhaps the damage can be mechanically polished off. Otherwise you have to either live with it or replace it.

Jon Barrows
Jon Barrows, MSF, EHSSC
GOAD Company
supporting advertiser
Independence, Missouri
goadbanner4
2003




Uglied up my Harley with oven cleaner

2004

Q. Ok! I've really done it now! A few years back I was using oven cleaner to de-grease and clean my bead-blasted aluminum Harley parts (cases, rocker boxes, cam cover, etc.). Well I went to clean up the bike today and sprayed oven cleaner on those parts and they all turned BLACK! (oxidation? Tarnish? Or whatever the reaction is called or spelled). Not a nice black either... This black is all streaky and did not want to rinse or wash off! It did not affect my polished aluminum parts...

When using oven cleaner in the past these parts would come out really clean with a flat, light grey finish that I liked.

Apparently the stuff I used today had something in it to cause the blackening that the stuff I used in the past did not have.

Question? What can I use to reverse or otherwise restore these parts to the natural aluminum finish, Without removing or re-blasting them or am I screwed?

When y'all are finished laughing, ideas for a solution will be appreciated...

L(DUH!)J

Joe Merola
Aging Biker! - Stumptown, West Virginia


A. I've used oven cleaner for years to strip clear and colored anodization off my aluminum car parts to prepare them for re-polishing and re-anodizing. It shouldn't hurt raw polished aluminum, but if they were anodized, then yeah, you're screwed. The parts will have to be re-polished (use the oven cleaner again first to make sure all of the anodizing is off) then re-anodized if you don't want to keep polishing them by hand. BTW, aerosol cans of carb cleaner is my degreaser of choice. Some brands can harm some paint finishes, but it is generally harmless and cleans parts fantastically.

Kelly Opfar
- Orem, Utah
2004


A. Be very careful when re-polishing and re-anodizing aluminum. If there are no critical features (threads or assembly fit features) then you will probably be okay. Anodizing is not just a coating. 1/2 your anodized thickness actually penetrates the material and removing anodize actually removes material that may not be able to be built back up in the re-anodize process.

Thomas J luniewski
- Minneapolis, Minnesota
2004



Q. Hi, I buffed out aluminum parts on my bike. They have a nice shine but you can see the white haze. Look at it from one direction looks good, another direction you see the haze. Does anybody know how to get rid of that nasty haze? Thanks --Dave

Dave Merhib
- Cherry Valley, Massachusetts
November 24, 2013




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