Any chemists out there? (Anodising question)

[greasemonkey]

I'm in the process of backdating an SC. The window surrounds and trim all have the black anodising (anodizing) finish. I would like them to be 'silver'.

My questions are - is there a way of removing this black finish and will the metal underneath be OK to polish.

I have spent ages on the trims under the rear windows (various grades of wet and dry and polish) and the result is fairly good. However, there will be no petrol left by the time I finish the window frames as it takes soooo long.

I have read some posts here that state using oven cleaner (Sodium Hydroxide) I used it neat and left it on for 15-20 mins but absolutely nothing happened.

Your help would be appreciated.

[peon77]

I would suggest finding someone to trade. I wish I could find some one local with black trim to trade. but if that doesn't work. Easy off oven cleaner is what is used to remove the anodizing. IIRC It has to have lye in it.

[1990C4S]

De-anodizing and Polishing Aluminum - RCNitroTalk

YMMV. I have no idea if this works....

[dw1]

There 's LOTS of information on removing anodize finishes & polishing, just search "wheel polishing" or related terms here. There also good info under "fan polishing".

Yes, oven cleaner will work, but you have to use the correct kind. The Easy-Off in the yellow can ("heavy duty") is what you want, not the stuff in the blue can ("low odor"). The stuff in the blue can, like most other non-industrial oven cleaners, won't do a darn thing. The Easy-Off in the yellow can will, because I've done it.

Oh, and don't leave it on too long or you can discolor the metal; it's better to use it multiple times than to leave it on for a long time. (You can probably guess how I know this.)

I've also had good luck just polishing off the anodized finish with a good fine industrial polishing media, an appropriate rotary tool, and a lot of patience.

[ghost1001]

I was in the same process; here are my thoughts and experience.

I removed all the trim and took the glass out. I then stripped the paint (mine was painted over) and anodizing off with a “fine” wire wheel on the bench grinder. This works well but then you must refinish the surface.

I tried “easy off” oven cleaner and that did not work. Wayne recommends using lye in the 101 projects book for stripping anodized wheels.

I also noticed that the trims on the car are made of different alloys. Now I am not sure if this is due to later additions or if the pieces are manufactured using different processes. The majority seems drawn or extruded, the exception being the metal trim on the exterior under the rear quarter windows. This appears stamped and I think is a slightly different alloy than the rest. It did not finish as well in my experience.

I think that even if you found a chemical means of stripping the anodized finish you would only be halfway home. I think you may still need at least 600 grit wet sand and polish. I achieved a very nice raw aluminum finish, but yes it is lots of work. To see details and pictures follow the link in my signature.

Kevin

[BGCarrera32]

I would look for a plating/annodizing company that perhaps does small or short run type work and helps out the motorsports crowd. Ask them to strip off the annodizing for you...the Easy Off oven cleaner trick is a royal pain.

You'll also keep your nose free of nasty chemicals and free up time to do other enjoyable tasks like waxing the car

[Soterik]

Originally Posted by BGCarrera32

I would look for a plating/annodizing company that perhaps does small or short run type work and helps out the motorsports crowd. Ask them to strip off the annodizing for you...the Easy Off oven cleaner trick is a royal pain.

You'll also keep your nose free of nasty chemicals and free up time to do other enjoyable tasks like waxing the car

I second this reply...

Another pelicanite is in the process of doing this with his wheels. He works in a fab shop so he has access to buddies who are subcontractors for him. He's had wheels stripped by some anodizers, and they required him to first strip off all the paint (170 grit blasted) so it wouldn't contaminate their chemicals. Note that the process of dipping the wheels and pulling out the anodizing does further strip material from the wheels, but this is what you "want" to do.

He's then polishing the wheels before re-anodizing, and then painting.

It's truly a lot of work the first time around on this as he's tested various grits, polishing methods and compounds, fabbed up a 5 lug tool to mount the wheel onto for polishing on a huge lathe, etc. He's reproducing the RSR finish on the first set of wheels, and based on results thus far it looks like they are going to come out about perfect...

He's going to backdate his window trim next, and plans on doing the same thing.

I believe I can get him to post.....

You may want to look into some anodizers that work in the airplane field, as the guys my buddy found do a lot of work for Boeing.

cheers,
Eric

[dw1]

Originally Posted by BGCarrera32

I would look for a plating/annodizing company that perhaps does small or short run type work and helps out the motorsports crowd. Ask them to strip off the annodizing for you...the Easy Off oven cleaner trick is a royal pain.

You'll also keep your nose free of nasty chemicals and free up time to do other enjoyable tasks like waxing the car

I also strongly agree. The yellow can Easy-Off stuff may work, but it does stink. If you go that way, be sure it is in a well-ventilated area.

Locally, there was a chrome/anodizing shop who would do this kind of work (and did a lot of work for bikers, including some work for OCC) but they are no longer available. There is another shop in my area, but they are "industrial" focused, and will do application of anodized finishes, but not stripping. Bottom line: chopper builders might be a resource, as well as custom paint & bodywork shops. Not that they can do it, but they might give you a good source.

[911pcars]

Sounds labor-intensive doesn't it? It is. And that's besides the labor to R&R the items from/to car.

Not sure how factory-correct you want to adhere to. One option to consider is to powder-coat the pieces. You have a choice of many colors, some can replicate the anodized look and will provide longer service life than anodizing. One owner applied a "titanium" finish that looked great (to me). YMMV.

Sherwood

[boston914]

Electoplating is a coating that is applied onto the surface of a metal.

Anodizing is a "chemical conversion process" which alters the surface of the base metal.

My understanding of the anodizing process is that the surface of the base metal is oxidized, which changes the appearance. (as opposed to applying a coating of a different metal)

A traditional anodizing process creates a "matte" finish on the metal.
Pigments are added to the chemcials during the process to create a color finish.

I believe that a chemical stripping process would be the best to prepare the metal for a different finish. This job should be done by a professional as the chemcials used in this process are nasty!

[911pcars]

Let's be realistic. Any attempt at anodizing at home as a DIY project has got to be serious, especially considering the dimensions of the trim pieces (e.g. door frame). If you insist on doing this, farm it out to a proven vendor.

Sherwood

[mkc1962]

I buy alot of unique auto restoration type stuff from a company called Eastwood. www.easwoodco.com. Though I have never bought any, they offer an anodize removal solvent that is supposedly water based. You might want to check it out.

EW Anodize Remover 16 oz Trigger style Spray

[mkc1962]

As for the repolishing. If its aluminum and you've got it clean, the proper buffing compounds, buffing wheels or bobs, and lots of time will make it look like a mirror. If its Stainless, unless your going to remove it dont even bother. A 3/8" corded drill with some home made mandrels will suffice. But to do it right, one really needs a shaft buffer. Obviously protect the areas you do not want to have buffed or scuffed, And do wear glasses or goggles. Trust me, buffing compound on the eyeball hurts. let me make this part clear. Metal buffing compounds, are not the same as paint compounds. They do not come in easy to use liquids, and even with the proper compounds, lots of work/time is needed. Most Metal buffing compounds are found in stick or very heavy past form. And NOT found at local parts houses. One more thing. When you place a certain compound on a wheel or bob, you need to dedicate it for life to that compound. That being said, If you need a certain size to acces a certain area, buy atleast 2, one for the primary rough buff, the 2nd for the finish buff. Think of it like you would when buffing out a old paint job. You use one pad for you heavy creme, then another for the polish creme, then another for the final finesse. Pad and buffs get contaminated, and you dont want try to do finish work with a grit infested pad. When you get things the way you want them. There is a products known as Zoops...www.zoops.com . Easily wipes on and will keep that part looking like new for years.

[boston914]

Originally Posted by mkc1962

I buy alot of unique auto restoration type stuff from a company called Eastwood. www.easwoodco.com. Though I have never bought any, they offer an anodize removal solvent that is supposedly waterr based. You might want to check it out.

EW Anodize Remover 16 oz Trigger style Spray

I have been out of college for a long time but I do have a degree in Chemcial Engineering. I have worked with and around chemicals for many years.

You should be very cautious about using this, or any other chemical products.

The term "water-based" is misleading. In this context, the products are called "water based" to differentiate them from "solvent based" products.

Acids and caustics are "water based". They are aqueous solutions (which means that waterr is one of the components).

Sulfuric acid (battery acid) and sodium hydroxide (an alkaline caustic) are "water based" but are highly corrosive.

Besides the risk of a chemical burn using these solutions, toxic fumes can be generated during use.

Again, I suggest that you use a professional to strip and/or re-finish your parts.

[jpnovak]

OK a little chemistry lesson.

Anodizing is a thin layer conversion of the base metal to its oxide. for example, in aluminum trim this is aluminum oxide. This can be done by chemical or electrochemical methods. The oxidation process is just a transfer of electrons out of the metal. They can be transferred to another molecule (chemical) or an electrode (electrochemical). Electroplating methods (racks and acid baths) are commonly used to get a uniform surface treatment. The bath is usually held at cold temperatures and pH 2 (highly acidic). The smoother the surface during electro-oxidation the smoother the finished anodized coating. This is why polishing is important prior to bright and clear anodizing. The current used during the electrochemical process can change the effective pore diameter. This is what gives a very fine pore (factory finish) or coarse pore (RSR-like)).

Once the anodizing (oxidation) is complete other metal impurities are added to give color. These impurities (dopants) bond within the aluminum oxide crystal lattice and shift the optical properties that give it color. You can also impregnate dye molecules into the pores provided you seal them up afterward.

To answer your question. Yes, a strong basic solution (lye, oven cleaner, etc) will chemically strip the oxide layer leaving the base aluminum behind. Of course, the same caustic chemicals will etch and pit the aluminum if the reaction is not stopped after taking off the oxide layer.

Be effectively "reversing" the voltage one can also electrochemically strip the oxide by reducing it to the parent metal. This takes more energy the oxidation.

I am not aware of the current best practice for industrial anodization. However, if you want good results I would recommend sending the parts out. I certainly would not want to build a tank full of sulfuric acid that would hold the trim. And I have relatively low standards for safety.

here is a good link to the practical aspects of anodizing aluminum.

Anodizing Aluminum

[greasemonkey]

Thanks guys, as I value my eyes/body slightly more than my window frames, I think i'll ship them out to be done as it looks either quite dangerous or VERY time consuming.

Thank you all for your input - this BBS is amazing.

Happy new year.