Anodizing

I have designed and constructed an anodizer for for the aluminium air-frames and parts. Over the next few weeks I will begin testing the process and will keep you posted and once I have proven that it works, I will produce a detailed video of the system and post it.

Why

When I think about it, it’s odd that I’m writing an article about anodizing on an RC aircraft website but then again, RC choppers and drones use plenty of anodized parts and even the electric motors in the Rhinos have anodized parts. The first question one of my fellow club members asked when he heard I was anodizing was why? “Well, firstly,” I explained,” anodizing forms a layer of corrosion on the outer surface of the aluminium and this protects the metal against further corrosion. Secondly it changes the properties of the surface and makes it much more abrasion resistant, but, the most important thing to me is that it gives it a great finish.

Just think about those anodized keys on your key ring, pull them out and inspect them, think about it. They’ve been bashing against the other steel and brass keys, in and out of locks, dropped and exposed but they still look great, not worn, not scratched and not dull. Beats the hell out of paint and doesn’t add to the weight.

Above all, I just think it looks hot…

My Method

Finally, I have managed to anodize my first Rhino fuselage, but not without issues. The anodizing system I have built was created without any previous experience in anodizing or any similar process for that matter. I watched the DIY videos on you tube and downloaded and studied the recommended material on the subject. Then it was a case of mentally formulating a process that would suit my needs.

My first consideration was the chemicals; I wanted to minimize the amounts needed. This would reduce the costs and problems associated with disposal. Also safety and floor space were high priorities. I decided PVC pipes offed the best vessels for the bathes I needed. The fuselages would be anodized fully assembled, 70mm high x 50mm wide x about 700mm long. So, I decided 100mm x 1m pipes would do the job.

The process I’ve implemented involves seven baths as follows:

(*Require heating)

Some processes include etching (using Caustic Soda) after degreasing. At this stage I have bypassed that process.

Heating

Three of the steps require heating. To achieve this I have mounted cheap PVC jugs and pumps to circulate the liquids though the jugs. In the case of the bye, it needs to be heated to a particular temperature depending on the colour. For this step I added a temperature control power switch which cuts the power at the set temperature.

Problems

As I stated at the start of this article, I have managed my first success using this method but it has ot been without problems and failures.

Safety and Clean Up

I won’t go through all the standard safety advice as you’ll get that with all the other material you read and see, I’ll just offer some of my added thoughts gained through the stuff ups I’ve encountered . The two bathes that I was determined to ensure did not leak were the acid bath and the dye bath, of course, these are the two baths that did leak. My advice which comes out of these events is make sure you set up in an area which is easy to contain a spill and easy to clean up. Also, keep a large bucket of water handy to dilute any spills, particularly on your clothing or skin which should be protected in any case. Naturally, take every precaution you can, if it can happen, it will.

Pump Problems

I didn’t give much thought to the pumps I use in the system; I simply bought cheap little submersible aquarium pumps. So far the degreaser pump has failed after very little use and still not giving it much thought, I replaced it with one that was bigger and a little more expensive. The problem is that I did not consider that I’m pushing hat degreaser through it and that these liquids are heated, submersible pumps rely on the surounding liquid to keep them cool. Oh well, I now realise these pumps will fail again and so I’m looking for a practical replacement. Perhaps non-submersed pumps offer a better way to go.

Anode and Cathode Distance

The oxidation of the subject part is caused by running a positive charge through the part which becomes the anode and a negative charge though the cathode with the acid solution carrying the charge between the two. I suspect that my anode is too close to my cathode however this requires further research and testing so I’ll keep you posted.

Calculations

I've created the Excel table below to calculate the surface area and the amperage and anodizing time. This table is embedded so it is not interactive. If anyone wants a copy of the interactive Excel sheet, just email me through the site and I'll send it.

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