Technical & Reference Section > Tech and Restoration
Adventures in Anodising
mivvi:
Hi Avro, Been following this thread from the start and just came back today and was chuffed to see it was a sticky :4_17_5:
I enjoyed the posting of your failures and obviously your successes! I love this kind of work and I work in research myself. So you got me on the track of having a go myself but have hit a brick wall and wondered if you may be able to help? I have everything set up and go through all the prosesses but when I take the piece out of the dye tank and put it into the sealer tank, the dye just falls off? I have tried various voltages/ampage/times but to no avail. Any help would be greatly appreciated. :daumenhoch:
Avro:
If virtually all the dye 'falls off' when put into the sealer then the anodising itself has failed. It can be incredibly frustrating. The blue calipers I did for Sleag40's Rickman were an example of this. Both sets of caliper arms were mounted in exactly the same way, connected to the same power source and anodised in the same bath. Both put into the same dye bath for the same time and at the same temperature. One pair of caliper arms came out lush, the other pair completely failed.
I have recently bought a length of aluminium studding which I have cut to various lengths. These lengths of studding are now my frames from which the parts are mounted. It is a further improvement, all to get the electrical connection as perfect as possible. What I would really like to find are cone shaped nuts that could be used against the part to be anodised (imagine the tapered end fitting into a drilling). This would do away with the small areas where no anodising takes place as a nut has been hard against the object.
I think titanium wire is a must, it was a suggestion made by a member on this forum that was golden. Aluminium just is not up to the job, too prone to deteriorate and too prone to spark erode.
To get going start by using black and seal the part in the dye solution, that is after the dying phase raise the temperature of that solution to 90 degrees for 45 minutes of so without ever removing the item from the solution. It will impact your electricity bill but worth it to gain confidence and experience. Most of my early attempts were done in this way and I did get good results eventually. Back to Sleag40's caliper arms, as one caliper arm was really good I decided to try to match it rather than start both sets of arms from scratch. After 20 minutes in the dye bath it was clear that they were a lighter in colour, this would only be made worse when put into sealer. I quickly decided to do the black trick and left the arms in the dye and ramped the temperature up to 90 degrees, the idea being to force more dye in and seal it in one operation. Worked a charm and both calipers looked identical.
It was only with later attempts that I used the chemical sealer, obviously desirable due to no energy cost. I make a fresh solution after every couple of runs.
Perhaps if you tell me what you are trying to anodise I can give you my times if the items are comparable? I keep a log book of all my attempts with times, amps, volts and temperature.
mivvi:
Hi Avro,
Cheers for your reply, I will let you know where I’m at. The rig is set up at my place of work and its my little my project. I work for a research company and a lot of parts I create need anodizing, so my boss said let’s make a rig up and do it ourselves. (He has no problem with me doing my bike parts either). Probably invested £800 in it so far, after constant failure, my boss has given up on the idea but I am patient and don’t give in easily ha,ha.
I have made a number of frames for suspending the parts, I am using aluminium welding rods to connect the test pieces, all fixings are bolted and have had no sparks or poor connections that I know of so far. I will need to look into the fixings you talk of too, once I get onto doing proper parts! So far I have placed nothing more than a flat piece of 2mm thick aluminium (12”Sq surface area) into the tanks.
The tanks I have are all heated: Degrease, acid wash, caustic acid, Sulfuric/water (Anno tank), dye and sealer tank. I then have De-smut and rinse sprays.
I am going to try and do the high temp dye/seal method you mention. This seems to make perfect sense. I need to order more dye to try this as my sealer tank is quite large and the dye tank is much smaller. Electricity cost is not a problem, as that’s all included in the rent for the workshop we have ;D
Thanks again for your help, let me know if its better to PM you instead of clogging up your thread. :daumenhoch:
Jon1971:
Great work mate. Might need you sometime soon if you fancy a bit of work. A few bits and pieces.👍🏻
Avro:
Anodising is about to re-start at my place. Bigger tank for bigger parts (and an even bigger tank waiting in the wings). Fingers crossed I can repeat my earlier successes.
Here is the new, bigger station:
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The left hand bucket is just water for rinsing the parts, this has to be done after each stage to avoid contaminating subsequent tanks. The middle bucket is a solution of caustic soda, the stuff you use for drains and oven cleaning. It is to clean the parts and strip any exisitng anodising from them. The bucket on the right is a solution of Nitric acid (it is actually a pre-made solution which I further dilute). This super cleans the parts and strips away any impurities from the base metal. The grey container is my new 20 litre anodising tank. It is filled with a solution of Sulphuric acid to a concentration of around 15% made from these liquids:
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All are filled and ready to go; I can not wait!
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