So this is part 2 of how I perform LCD II home anodizing in my garage. If you missed part 1 you can view it here. In part 1 I had dealt with surface preperation and cleaning. Part 2 will demonstrate the remaining steps 3,4 and 5 which will finish the parts off with anodizing, dyeing, and sealing. Enjoy!
This is the step that everyone wants to hear about. If you have decided to skip over reading steps 1 and 2 that I posted yesterday then I would like to reiterate a previous statement of which I said “if you spend 5 minutes completing a project then it will look like you spent 5 minutes completing the project”. However I also said that this is not an instruction guide so let’s move on shall we?
The basic physics that surround anodizing are fairly simple. You take your aluminum part and suspend it in a bath of sulphuric acid and then run electric current through it. There is lots of information out the internet that explains all of this if you care to research it further. The set up I use is based on a 5 gallon plastic pail. Although my set up is small it is easily expandable into larger containers to accommodate larger projects. My 5 gallon bucket has a mixture of battery acid and distilled water in it. I mix the solution 3 parts water to 1 part battery acid (by volume). I struggled with this ratio initially however I have since located documentation which helped me dial it down to the 3:1 ratio. As I previously stated this post is not and instruction booklet and that there are certain safety precautions to be taken. Right now is the only warning I am going to give. AAA = ALWAYS ADD ACID! When mixing a sulphuric acid solution you never pour the acid into the bucket first and then add water. ALWAYS pour the water in first and then add the acid.
With the acid in the bucket I now needed a cathode. A cathode is a metal electrical conductor that will be hooked up to the negative side of the power supply. When anodizing the 2 most popular types of cathodes are lead or aluminum. I opted to build a couple of cathodes out of 6061 aluminum sheets and then gave them a bend to help them hug the sides of my bucket. The size of the cathode is I important. It needs to have at least the same square inch area as the part is that I am anodizing. As far as I know a cathode size in excess of the anodized part is not a factor.
Now comes the anode which is the metal electrical conductor that is hooked up to the positive side of the power supply. The anode is the part that I am anodizing. The anode needs to be suspended in the sulphuric acid solution. To do this a wire needs to somehow be attached to the part. I have been using up my 4043 aluminum TIG welding filler rods to do perform the task. I need to ensure I have good contact between the filler rod and my part in order to obtain a good flow of electricity. I usually end up bending the filler rod to gain a certain thickness and then I force it into a threaded hole of the part. Every situation requires some ingenuity.
There are many different ways to build racks for the anodizing tanks. Mine is not great however I will spare you the details. Improvements can be made with experience. My aluminum 6061 cathode plates are placed into the bucket of sulphuric acid and the negative side of my power supply is wired to them. I then hang my anode (the part I am anodizing) to the rack that sits on my bucket and connect the positive side of my power supply to it.
At this point we need to take a slight detour however this is a good detour. The following information is what spares newcomers from massive amounts of frustration and failure. It has to do with figuring out how much current to run through your bath and for how long. Again I feel like I need to reiterate that this is how I anodize, there are other ways however I know, from first hand experience, that this way works. I use what is called the 720 rule. The rule goes like this. It takes 720 minutes at 1 ASF (amp per square foot) to anodize a part with a 1 mil (.001”) thickness. Now if you are like me I was thinking that I had to run my part in the solution for 12 hours. No you don’t and this is why. This home type system uses LCD (low current density); I am not going to explain this as it is irrelevant. What this means is that I am going to use 6 ASF to base all my calculations from. Why 6 ASF? Again…at this point it is irrelevant for this post, email me if you really need to know. All I will say is that 6 ASF proves to work well for Type II anodizing. So on with the math. If we anodize with 6 ASF to obtain 1 mil thickness then based on the 720 rule we only need to anodize for 720/6=120minutes. That’s right 2 hours. Can you cut that time down? Yes however your thickness will not achieve the desired 1 mil. Who cares if it isn’t 1 mil? 1 mil creates deeper pores which allows for the colored dye to soak in and produces better colored results. Are you still with me? Good let’s keep going. Next step in the calculation is where I need to know how much surface area is on the part I am anodizing. The 720 rule is based on 1 square foot of surface area. If I want to anodize a flat piece of 6061 aluminum that is 2” x 4” x .125” thick I need to add up the surface areas of all 6 sides. I won’t perform the math in front of you however the total surface area of all 6 sides is 17.5 square inches or .122 square feet. Since we require 6 ASF per 1 square foot this would equate to requiring .73 amps of current (6ASF x .122 sq ft) for .122 sq ft. So there you have it. What I need to walk away with at this point is that I am going to anodize my sample part for 2 hours at a Constant Current (CC) of .73 amps for 120 minutes to obtain 1 mil (.001”) of thickness. If you can’t, or do not want to, comprehend this then go to this handy online calculator that will do the math for you. You can even run my sample numbers in it to double check my work.
In the case of my demonstration trigger and receiver I calculated out the total square inch surface area to be 31.58 sq. in. which results in a target current flow of 1.32 amps for 2 hours in order to achieve a 1 mil anodized coating.
So let’s get back to the anodizing. I have my part suspended in my bath, my wires hooked up and I am ready to flick the power on. But wait…what exactly am I powering up? Yes you need a power source. I use an ASTRON VS-50M 15 volt 50 amp DC power supply that I was able to pick up used. Some people use manual battery charger and some use car batteries. I cannot comment on these methods. Using a controllable power supply allows me to abide by the 720 rule. If you haven’t already done the math you will note that a 50 amp power supply limits me to anodizing a part no larger the approximately 8 square feet (720 that one). On my power supply I always max my voltage and allow it run where it wants. The power supply is capable of providing 15 volts and typically runs around the 13 volt mark. It is the current I limit. Since the ammeter on the power supply is not accurate enough for me to dial in small current I simply install my DVOM in series with my positive wire which allows me to control the currently accurately while I monitor it with my meter.
So there you have it. The anodizing process is under way. I have set my timer for 2 hours and things are starting to bubble. Since it is now a waiting game I will take this moment to mention a few things that relate to the anodizing tank. First one is temperature. I anodize with my sulphuric acid temperature at 72 degrees F. If the mixture is a bit cold from sitting in the garage I have a 150 watt aquarium heater that I use to bring the temperature up. I should note that the anodizing process creates heat and why wouldn’t it? If you think about it and you anodize a part that is 8 square feet it would require 48 amps of current for 2 hours. That’s a lot of current which will start to create a lot of heat. You need to keep the heat under control. Some set-ups use ice and others use cooling towers. In my case I use nothing because all my parts are so small that the temperature in the bucket only ever rises a few degrees. When only using a few amps to anodize the heat is not a factor.
Next thing to bring up is the agitation. I have read that some people use aquarium pumps to agitate the sulphuric acid bath while the part anodizes. I figured I have a huge tank of compressed air sitting in the corner so I wasn’t going to waste my money on a pump. I took some ¼” plastic air hose, the stuff used for pneumatic cylinders, and created my own set of 4 air jets. I hooked them up to a regulator and have myself a very low pressure, low volume agitation system. Do I need to agitate? I don’t know I just do. I believe there are many others that do not.
While we wait for the part to anodize I thought I would mention that anodizing stinks. If you have ever smelled a sulfated car battery then you will know what I am talking about. I have a ventilation fan in my garage that I run. I am not sure I would ever anodize in my house. Apparently there are products available that eliminate the odor however I have no experience with them.
As the parts anodize you will start to see the aluminum part change color along with the wire it is suspended from. The part goes from a shiny metal to more of a dull grey. This is good. If it doesn’t it is possible that the part has a bad electrical connection.
Throughout the 2 hours of anodizing I occasionally check the amperage and tweak my current to ensure that I maintain the calculated current required.
So 2 hours has passed and this is where all the hard work starts to pay off. This is also where the fun comes in. After 2 hours of the part sitting in the bucket having electrons forced through it it can now be taken out and rinsed with distilled water from the spray bottle. And that is it! The anodizing process is complete. From here the part can either be dyed and sealed or just sealed.
The dye process is quick, easy, and highly satisfying. At this point the pores in the anodized part are opened right up ready to suck in whatever dye color you choose. The process I use involves the same kettle I used in the SP Degreasing process that I outlined in part 1. I dye all my parts in a colored solution heated to 140 degrees F. DO NOT heat the dye too hot as the pores in the part will begin to seal and the dye will not take. Once I have brought my dye temperature up to 140 degrees F I pour it into a suitably sized plastic container and then suspend the part into it. The maximum amount of time a part can stay in dye is 15 minutes. After 15 minutes the part will no longer take on any more color and all you are doing is wasting time. However 15 minutes is the maximum were as there is no minimum. Dyes will color to a different shade depending on how long the part is submersed in it. I have found that with my darker colors like the browns, grays, and dark blues they benefit from only 2 -4 minutes otherwise they get too dark. The reds, greens, and brighter blues work nicely in the 8 minutes range where as the violets, yellows and oranges can handle the full 15. It comes down to experience and the shade of color I am trying to achieve. That is all there is to the dyeing process. It is over fairly quickly.
I shot the following video while I dyed the Electric Blue receiver. The video is meant to show how dye time affects shade. I’m not sure the footage captures the affects all that well, it is what it is. The video is just a bit over 2 minutes long. The first minute shows the effects every 15 seconds, the last minute shows clips of the remianing 5 minutes.
Sealing of the part is the final step to the anodizing process. Sealing closes up the pores created by the anodizing process and locks the dye in. The process is pretty straight forward. I suspend the part into a pot of boiling water for ½ hour. That’s it. After half an hour the pores are shut and the dye is locked in. I take the parts out of the boiling water and straight to a white polishing cloth and not a spec of color is evident on the cloth.
When I first started to set up for anodizing I had read through the process and realized that part of the challenge was to collect all the equipment you need to do it. There are places on the web that will sell you complete start up packages that include everything you need. One of these places is Caswell Inc. and they have 2 warehouses located in both the US and Canada. If you check out their site you will be able to find the complete kits and supplies you may need. I am not going to give Caswell Canada top praise as I have run into minor issues with them however they have always provided me the supplies I have ordered in a timely manner therefore I can’t really complain. I will continue to use them.
I did not start with a complete kit instead I opted to piece mine together my way. There are not a lot of “hard to find” items that you need. The following is a quick run down of my equipment;
- Battery Acid; purchased from a local automotive parts supplier in a 20L box for around $28 (I think)
- Power supply; my Astron VS-50M was found online used. I paid approximately $180 including shipping and had it sent to me from the other side of the country.
- Dyes; $13 per color purchased from Caswell Canada. The dye comes in 4 oz bottles in the form of a concentrate. 1 bottle is added to 2 gallons of distilled water. Dye lasts a long time and can be used over and over.
- Distilled water; purchased from an industrial supplier and bought in 20l box quantities for around $7. I go through a lot of distilled water when initially setting up my tank and dyes. I must have used over 150 liters by now.
- SP degreaser; purchased from Caswell Canada for $26. It comes in powder form that gets mixed into distilled water. 2lbs worth will make 4 gallons
- Aluminum de-oxidizer and de-smut; $23 for 1 quart from Caswell. 1 quart gets combined with 2 gallons of distilled water.
- Heater for my anodizing tank; $35 for a 150 watt aquarium heater purchased from a local pet supply store
- Aluminum hanging wire; not sure of the price on this one. Aluminum wire can be had from any welding supply store. I use TIG filler rod however the wire can also be had in spools for MIG welders. Not a lot of money
- Cathode; like I said earlier either 6061 aluminum or lead can be used. I used 6061 that was picked up from my local metal supplier. More then enough cost me around $25. Lead sheets (used for roofing?) can apparently be had at your local hardware store, again, unsure of the cost.
- 1500 watt kettle; $10 on sale from any place that sells home small appliances.
- Electric hot plate; $25 from a small appliance store
- Other items like plastic containers, digital timer, thermometer, spray bottle, dish soap, scrub pads, etc, can all be sourced locally.
I think that is it for supplies however I am sure I have missed something. If you want clarification then send me a message.
Some people dedicate a certain area to set up their anodizing line. This has a huge benefit off being able to work more quickly and in a more organized manor. I have to prioritize what equipment takes up my space and right now anodizing is not at the top of that list. My whole set up is portable and all the equipment gets stored in a plastic bin and kept on a shelf in the garage. The only portion of the entire set up I keep in my basement are the dyes simply because I have space there to sacrifice.
And there you have it. My methods fully exposed. My fingers hurt from typing all this. I need a break…I’ll be in the garage.