Technical & Reference Section > Tech and Restoration
Adventures in Anodising
Avro:
I have six days off work and had planned a spring clean and BMX restoration/build work. I needed the down-time after a hectic few weeks at work and was looking forward to it. My hopes were dashed this morning with a recorded delivery letter from my landlord to leave; two months notice given. I have often wondered if a casual view of my kitchen would instill visions of a meth lab but I have no knowledge of the landlord being in the flat of if he/she is a Rad member (giggles). Truth is I am a private tenant who dare not ask why.
Two months will fly by I know so I will have to look for a place asap, but also look to progress threads I have posted here. This may seem odd to some but the whole BMX thing has become a retreat, an indulgence and something I have enjoyed.
Therefore my hand was forced and, notice the leave letter in hand, I thought lets have a go at those pedal cages! I had already atempted to anodise the cages, my first ever attempt, and the results, were not too shabby. Some very rudementary lessons learned and a lot of experience gained along the way. Since my last post in this thread I had decided to put a lot more effort into preparation work, being that any paint job, or similar work, will always reflect the preparation time put in.
So here goes. This is actually my third attempt with the cages. To recap, the first attempt had the cages arcing with the suspending wire and eventually falling to the bottom of the tank due to erosion. The second attempt was very encouraging although patchy and revealing of underlying finish issues.
I stripped the cages again in caustic soda solution and desmutted for good measure. I then decided to prepare the metal more aggressively than before. I bought a palm (mouse) sander and a plethora of papers to begin the refinishing process, I also bought a plethora of wet and dry papers to work towards a finished patina. I used the papers from p80 to p120 to p240 with the palm sander until most of the scratches were gone or very faint. Deeper scratches, and one cage had several that would have to stay; they were either too deep or traversed stampings. Once a consitent patina was achieved with p240 I moved on to hand sanding with wet and dry, lubricated with water and a tiny amount of fairy liquid. The hand sanding went from p400, to p800, to p1200, to p2000 and finishing with p2500. Hours or work but goal orientated. I decided to leave the cages at p2500 and not polish; thinking this finish looked very consitent and acceptable (deep scratches excepted that to remove would have destoyed the cages).
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Avro:
....so I then connected both cages to a length of aluminium wire and then dipped in to caustic soda solution until a uniform brown/black appearance was evident. Then they were dipped into a nitric acid solution (desmut) where the impurities are removed and the metal surface returned to a uniform aluminium lustre (more dull than what p2500 delivered). Throughly rinsed in de-ionised water and then into the anodising bath.
15 minutes in and the voltage has ramped up to 16.6v maintaining 1.17amps
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30 minutes in and voltage at 16.3 - 16.6v maintaining 1.17 amps
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1 hour in and 14.9v (close to optimum) at 1.17 amps; really good fizz from both cages.
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1 hour 15 mins in 16.9v holdign 1.17 amps; suspect one cage connection has eroded and therefore concluded the experiment although, given surface area estimates, still with in tolerance.
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oldschoolace:
Love thread like this, keep it coming :daumenhoch:
Avro:
...ok I am having terrible trouble putting pictures where I want them, the system of uploading pictures and then attaching seems out of whack. I will have to give up on the progression of the anodising process, complete with power outputs for the anooraks (like me). I have tried several time now and I just give up. The way you attach a photograph, and the order you upload it, makes no sense. Grrrrrrrrrrrrrrrrrr. May have to try the third persen route and use a hosting site but meh...cross.
Avro:
....sorry for the lack of progress photographs, I like to see them so assume others do. The end result is 'puffs out chest, praised mathematics and chemistry, clears throat and declares 'SUCCESS'.
'puffs out chest a little more' the black colour is completely uniform. It is also very hard. I had previously anodised some brake calipers and they looked good but truth is I managed to scratch off the black surface with my nail on the edges of the casting. The coating on the cages is solid, like it should be given it is similar to sapphire.
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These are as they have dried out of the final rinse in de-ionised water. Once polished they will look like new. Sorry to sound so triumphant but I am thrilled. I guess I knew it was all about the preparation, and that is where all the time is. It makes no sense financially but the sense of 'omg' is high, at least when you first see the part out of the rinsing water.
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