Steel Charlie

So the recent acquisition of the LeMond reopened my search for cheap ano stripper. Buried in the google search pix was a youtube thing some bike guy made stripping a chainring with ZEP Industrial Purple Cleaner and Degreaser Concentrate. Impressive! HomeDepot and $12 got me a gallon of it.
First in was a chunk of black seat post that I had chopped off some time ago just for this purpose. Used a pill bottle for the bath and tossed in the piece. Took 10min to produce the result in the pic. I was like WHOA ! Went out to the bike and snagged the stem cap, bar clamp, and seat clamp. Same pill bottle got the cap and bar clamp. The 3T anodizing was a bit tougher/thicker and those pieces took about 30min each. the seat clamp went into a small plastic cup thingie still using the same fluid I started with. It only took about 10min like the seatpost.
The stripper threads always have some caveat about too long so I'm gonna toss the post piece back in the bottle and leave it overnite just to see. I'll let you know tomorrow. So here's the pix - none of the parts have been anything but just brushed off after the strip

dddd

Did the anodizing go away to where you could use metal polish straight away, or did it just bleach out the black dye from the anodized surface?

Either way, you're off to a good start. I have bought zero-offset seatposts that needed "bleaching" using oven cleaner, but recently I've been buying the generic brand UNO posts (not genuine Kalloy afaik) that are offered in silver with just a painted-on logo that I remove using Gumout spray cleaner applied for ten minutes to a cloth blotter strip wrapped around the post at the logo and sealed with plastic wrap (it is a stubborn paint and I want to protect the silver ano finish, so no abrasives).

unworthy1

That's impressive and should be much safer to use than lye (or even lye-containing oven cleaner). I was warned that Castrol Super Purple cleaner could "etch" aluminum over time so never left any pieces in that stuff for long. But now if I WANTED to strip off anodizing...wonder if it works as well as this ZEP Purple?

dddd

I bought a pair of Nuovo Record derailers where someone had soaked them in some kind of degreaser(?) that left the alloy black, and have been wanting to know how to replicate this.

Anybody know how, which chemical has the effect of producing the durable dark-grey tone?

unworthy1

Interesting! I know when you soak (any color) aluminum in lye there's a black residue left on the metal, but that rinses off with water, maybe a little scrubbing. Perhaps if you let it air dry it might become "permanent"? I don't know and would only experiment with something I didn't care about. Otherwise never seen this effect, you can get dark oxides on steel and ferric metals with an acid-soak (phosphoric for one)...not what you are describing, tho.

icemilkcoffee 

Very nice results. But have you put the bolts back in there yet? I worry about the threaded holes being eroded by the solvent.

Steel Charlie

Not in the strip long enough for that to be a problem.

UPDATE
I went ahead and tossed the stem in the stuff. Used a cut off sport drink bottle for the bath. Took about 1/2hr and came out like the bar clamp. OK by me. I put the seatpost piece back in the pill bottle and the stripper. After an hr it was still fizzing pretty enthusiastically so I had to assume that it was after the aluminum since there was no black left to burn. The metal looks fine after up to the 1/2hr I've seen but long term may not be a good idea. Cannot find a downside to just a bit of attention to the process as the results are just way fine IMO. Pretty much TabA/SlotB AFAIC.
Charlie

oneclick 

Might have been oxalic acid, if he tossed them in whole; aluminium in contact with steel will turn a dark grey in such a bath.

unworthy1

Just a slight hi-jack, but when you dissolve the anodizing (artificially thick aluminum oxide layer) that has color from added dye, you remove the coating WITH the dye/color and the resulting aluminum is said to be "raw" so can be polished. It's also the nature of aluminum that on exposure to air (even briefly) there is a natural aluminum oxide that forms, it's the same stuff that makes "anodized" coatings but is quite thin and has no color. Assuming this ZEP cleaner has something caustic (a base versus acid) as well as strong surfactant (detergent) then it's doing what other caustics (lye and oven cleaner) will do: it will strip aluminum oxides (thicker coatings take longer) and the question I have is: same for paint and powder coating? Or do they just get made "dull"? (wondering cause that 3TTT clamp piece looks like it might have been a painted finish, not anodized)
I'm going to make the same test with Castrol Super Purple and will report back what that stuff does.

Steel Charlie

No the 3TTT stem was anodized with screened logos. It all came off. And yes it is a caustic solution. I haven't tossed any big paint into it but caustics eat organics (like skin) and that would include any oil based paint at any rate. I don't know that I have any powder coated something small enough to test. It's in a plastic bottle and I had it in a couple other kinds of plastic containers that seemed to ignore the Zep as would be expected.

BTW while searching for the strip I noticed that there were a number of DIY anodizing links too so that is out there as well tho I had no interest in it.