Any question answered...

Has anyone renewed their British passport recently?

What's the go? How long does it take? Do you post it off or can you just ask them to send you out a new one before the old one expires?

Hmmm caustic soda crystals is natriumhydroxide pellets as linked too.

I planned on dumping them in the solution, your solution with the brush is more foolproof.
Catch is though that my gxp cranks have an attached steel axle and as per tester it runs into the pressed cavity between aluminium and steel which is hard to rinse out so just keeps on dissolving the alu from the axle.

I can do a middle ground; keep away from axle and do the ends to save myself from sanding the whole thing.

I'll have an experiment at the weekend to see. Many thanks for your comment too

I did the fast-track, £70 more than the normal fee, got it back within 3 days of the brief processing appointment in Victoria.

caustic soda crystals is natriumhydroxide

ah I did not know that!

It's the method that I've used many times and I haven't completely dissolved a bike part yet...
With the race face cranks I linked to, it was easy since both arms can come away from the axle.

I actually have a set of Sram SX mtb cranks that I'm going to remove the anodising from, but these have the drive side arm attached to the axle like yours.
My plan is to leave the anodising on around the axle/crank interface since it wont be visible when installed on the bike.

Previously I used a large tupperware box that the crank fits in. I filled it with the caustic soda solution to a depth of about 10mm and sat the whole crank arm in it and used to brush to coat it then rinse and repeat.
I'm going to use the same method for the sram cranks but make sure that none of the solution contacts the axle/arm interface. I think if I'm careful it won't be a problem.
Once the cranks are polished and installed, it won't be visible.

fwiw before I ever tried to remove the anodising on anything of value, I practiced on old headset spacers just to get a feel for how quickly the reaction happens.

Good luck!

edit - if I get round to doing my own cranks over the weekend, I'll take some step by step photos

Do you have to show up in person to get it done?
For my Aussie one I just did the online thing and it arrived (a long fucking time) later.

Fast-track you need to go in person to an office in Victoria, whole thing took ~45 mins, I'd booked 2 hours out of my work diary so I had a pint in the pub opposite afterwards...

There is/was a decent craft beer pub near that place. I went there after my citizenship interview thing. Not in any rush so will have a look at the non fast track option.

Yet again lording your high cost lifestyle over us.

Beware; the steel axle is also visible from the drive/outside, the dark gray ring as per image.

As tester pointed out this interface is only pressed, so get any caustic soda in there it'll dissolve the aluminium round the axle which you don't want.

I believe your method with the brush to be quite smart and will use it in conjunction with wetndry where I don't want the caustic soda to end up.

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I applied for a new one after my old one expired during COVID. Didn't pay for fast-track but got it back within 2 weeks.

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very good point, I don't have my cranks to hand and had forgot about the axle being exposed on the other side! Softly softly approach should do the trick. Do post up your results when its done :)

You know that I have no interest in your overly-flavoured craft lager....

natriumhydroxide

aka sodium hydroxide/caustic soda/NaOH/lye

Can we please stop calling it natrium though? I think no one has called it that since the olden days when we thought stuff burned because it contained phlogiston.

Tester is from the olden days though.

Just done mine via normal route took about 2 weeks, you have to send old one before they will send new one

I'm not the one who called it Natrium. To be fair to Rodolfo, he's obviously a forrin, a lot of them don't have vernacular names for the elements.

I guess that would've been a good time to do it :D

I thought you might like that. Which is why I left the best bit out.

It's actually called "CASK" and has 10, yes 10, ale taps.

Yeah, so it has to be timed right.

I've got my BLUE (hahahahaha fuck Brexit) Aussie one though so actually, fuck it. Can do it any time I guess. Cheers peeps

Did it online, posted my old one back, fresh one arrived 3 weeks later.

Edit: this was in July/ August time

aieaie, dutchman in berlin. very forrin.

that´ll be one for next weekend though; work calls so i wont be fizzying off anodising this weekend unfortunately..