smd4

Is it possible to lightly polish clear anodizing without going through it? Would it even be noticeable?

FBinNY 

If you mean to clean it of something like dried oil or tar, then yes, if you're careful


If you mean to make it shinier, then absolutely not.

smd4

Thanks.

KerryIrons

Try a wax/polish. Even furniture polish. There are a number of polish/cleaners available designed for stainless appliance fronts.

Mr. 66

Instead of polishing the anodized I'll use car wheel cleaner, spray on and rinse off, and a very light brush to remove the muck that water alone did not.

t2p

I use Mother's Mag and Aluminum polish on a large number of items

might work for your application

smd4

Thanks everyone. I don’t want to remove the anodizing. I don’t think I’ll be able to get the shine I’m looking for unless I remove it.

masi61

which specific part are you considering removing the anodizing from?

smd4

I don’t want to remove any anodizing. I was wondering if it might be possible to get a higher shine on some of my standard DA 7700 parts to more closely match the 25th Anniversary parts I have (brakes and RD). There’s nothing wrong with the standard finish; it’s pretty well polished as is, so it’s not worth the risk for a modicum of improvement.

masi61

If the defect in the clear anodizing does not go all the way to the raw aluminum, it might be possible to use several grades of heavy cutting rubbing compound and working up to a fine grade polish which could the be waxed with a high grade wax like pure carnuba wax.

if the defect does indeed go all the way through though, I have noticed that Shimano clear silver anodized parts can get some strange white tendrils of corrosion that seem to travel under the clear anodizing. When that happens your serviceable vintage 7700 part is more user grade and not show quality anymore. Yes, this is kind of a shame. To perfect these parts to the 25th anniversary level of polish, the cranks would be the easiest to strip the anodizing and put a mirror polish on. The brake arms, the aero brake levers, the shifter paddles & pivoting parts of the front and rear derailleurs would be much more difficult to polish back to perfection due to all the rivets, bushings, locking pins, etc… that make the contours of the part much more convoluted. Any amount of road rash can make ugly that formerly lovely part.

I think there is a component restoration service in Australia that will do mirror polishing on 7700 bits but it is expensive and I believe the results could be variable, not to mention that mirror polished raw aluminum needs to be freshened up with metal polish whenever it is ridden in the rain for example. If you enjoy polishing parts and have the time for it then it is possible to keep your vintage parts looking jewel-like.

What would be really cool is if said restoration company could make a titanium bolt kit and also a kit with stainless hardware for the pivots & slip pins and such that substitutes circlips at the pivots and would permit a full teardown & rebuild by the average weekend mechanic.

FBinNY 

FWIW- Anodized parts vary greatly in luster, from a satin finish to a fairly high shine.

The degree of shininess depends on the metal BEFORE anodizing and the degree of etching when anodized.

Getting a shiny end result calls for polishing the part, then using minimal etch when processed.

smd4

That’s pretty much what I thought, but I wanted to confirm with you guys.

SJX426 

The 7402 crank set in my stash has an issue with finish. The solution appears to be simple to strip the ano and polish.
P1030625 on Flickr

maddog34

Anodizing 101.

What is Anodizing?

Anodizing is an electrochemical conversion process in existence since the 1930s. Several metals are capable of being anodized including aluminum, magnesium, titanium, and tantalum. Anodized aluminum is used in many applications due to its low cost, aesthetic qualities, and ideal mechanical properties.

Unlike most protective coatings, anodizing permanently changes the outer structure of the metal. When aluminum is exposed to air it naturally develops a thin aluminum oxide film that seals the aluminum from further oxidation. The anodizing process makes the oxidized surface much thicker, up to several thousandths of an inch thick. The hardness of the anodized aluminum oxide coating rivals that of a diamond, enhancing the abrasion resistance of the aluminum. The added depth of the oxide layer improves the corrosion resistance of the aluminum, while making cleaning the surface easier. The porous nature of particular types of anodizing makes it possible to dye the aluminum a variety of colors, making it more attractive.

Anodizing typically ranges up to 5 mils thickness.The three most common variations of aluminum anodizing include chromic anodizing (type I), sulfuric anodizing (type II) and hard anodizing (type III).

• Chromic anodizing utilizes a chromic acid electrolyte and yields the thinnest coatings, only 0.02 to 0.1 mils thick (0.5 to 2.5 microns). 50% penetration into the substrate and 50% growth over original dimensions occurs. Chromic anodizing has the least effect on fatigue strength and is less corrosive, thus ideal for complex and difficult to rinse parts. Excellent for coating aluminum castings, most chromic anodized parts are used in military and aerospace applications and are more functional than decorative in nature.
• Sulfuric anodizing is the most common method of anodizing, utilizing sulfuric acid to yield coatings up to 1 mil (25 microns) thick. 67% penetration into the substrate and 33% growth over original dimensions occurs. Due to its permeable nature, sulfuric anodizing is excellent for color dyeing and provides a base for primers, bonding agents, and organic coatings. Sulfuric anodizing provides corrosion resistance and is very durable. Typical applications include architecture, aerospace, manufacturing, automotive, and computers.
• Hard anodizing (a.k.a. hardcoating) utilizes a higher concentration sulfuric acid electrolyte at a lower temperature resulting in a tough outer skin with excellent abrasion resistance, corrosion resistance, color fade resistance, dielectric strength, and surface hardness (Rockwell C-Scale up to 70). 50% penetration into the substrate and 50% growth over original dimensions occurs for a total thickness of 0.5 to 4 mils. Hard anodized metals have heightened surface roughness. Common uses include non-decorative food packing equipment, photocopier paper rolls, and exterior applications such as building storefronts and windows.

so.. IF you want to be brave, you can clean up the part in question a bit,. but working too much in one area or another could have you removing the entire coating and then dealing with occasional oxidation.. I've salvaged a rather disgusting looking pair of chain rings recently, and a very ugly, but FREE, 105 triple crank set also comes to mind... the crankset took the better part of two DAYS to refinish/polish.... i'd try steel wool, 0000 grade, first... with a bit of penetrating oil(PB Blaster)... work a backside area as you learn.... it won't take much to go right thru to bare aluminum, so be gentle... bike parts are typically anodizing type #2... THIN... my "Refinishing" used 400 grit, 1000 grit, then 0000 steel wool/light oil... that 105 crank had some nasty scratches that needed removed too...