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Anodising


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Anodised Aluminium is that very hard and often beautiful coloured finish you find on Aluminium components you buy. It is a hard wearing, scratch resisitant and corrosion proof finish, ideal for the marine environment.

Anodising is fairly easy to do. It does however, require a large quantity of Sulphuric Acid and thus reguires some caution and clear thinking. To colour a component is also very easy to do, however, the colours themselves are derived form quite expensive and very toxic metalic dies. The biggest issue wiuth these dies are disposing of the stuff once it is finished with. So I choice to leave colouring alone and stuck with the natural silver finish. Which in all I did, looked very good anyway.

The term "anodise" (ize) comes from the fact that the electrical current is connected as positive to the component being processed and that in electrical terms is called the Anode. The cathode is the Negative connection. What takes place is a Crystaline structure of Aluminium oxide builds up on the surface of the Aluminium. This structure is a microscopic matrix of capillaries. The longer the time, or the stronger the electrical current, the thicker that matrix becomes. By the way, the surface grows or increases in size. We are talking very very small of course, but the component does not shrink in other words. Important to understand if you are making a component to fit into another.

At the point of where the component is removed from the bath and washed, the process of colour follows by simply dipping it in the bath of dye. So if anyone does wnat to colour, that is where that part of the process occurs. From that point, it is then dropped into a bath of boiling water. The matrix closes up and locks the dye, or in our case, simply locks the matrix up and the finish is created. By the way, this finish is also no conductive.

There are several, in fact dozens of different standards of finish. Each is achieved by a slightly different process. Many from variances in Acid types used. We will be looking at just two easily obtained standards. Type 2 and type 3. Type 1 uses Chromatic acid and is not something easy to play around with. The T2 & T3 uses Sulphuric Acid. Great caution is required with handling of this acid. But it is cheapo and easy to obtain. I obtained it from a Marine/Auto Electrician that supplied new Batteries and the Acid comes in about the right strength right out of the container. However, a strength of 10 through to 30% can be used.

There are three variables used to obtain the T2 & T3 finishes. Electrical Current, Time and temperature. Variances in these three determin the thickness and the actual size of the crystal structure grown, which ultimately results in the components "toughness" at the end of the process.

The only other things you need will be a Tank large enough to fully emerse the component/s and the more difficult part, a bath of some kind that you can bring water to the boil in that will also fully emerse the component. That was actually the hardest part I found when anodising the mast spreaders for my rig.

Then finally, a Power supply. Preferably one you can observe and vary the current with. The larger the component, the more current you require. So if you are anodizing a large component, it can really take some current. I varied from a small self made PS of about 10A for small components right upto a welder for the large stuff. A welder works very well by the way. You can't actually over supply Current as such. What does happen is that the more current supplied, the fater you heat the bath of acid. For the types of finish we are after, we require the bath to remain cool. The cooler the better. That's the hard part of the bath. Some instances require the bath to be cooled and so you may need to sit your acid bath inside another larger container that has cool water circulating. Keep the acid cool causes a faster and thicker hard wearing oxide to be biult up. Allowing the acid to get too hot can cause some of the structure to close up and worse, the fumes from acid are dangerous. In fact I should add here that good ventialtion is required and a fan is pretty much essential. You don't want to breath acid fumes and you certainly do not want to have acid fumes around your workshop, acid it will corrode the surface of metal parts very quickly.

the next chapter I will get into the actual set up.

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Pictures?? Do I get extra credits :wink:

 

Set ups can vary from a very simple plastic lunch box to very elaborate Lab type environments. What ever you set up, you have to ensure one important aspect throught out, and that is your safety. You will be using Electricity, Acid, Alkaline and Boiling water. And if you are like me, the more dangerouse thing you may have to deal with, is the wife! Especially if you use the Kitchen to boil the water, or her pots, pans and other utensils. All these process will pretty much ruin the looks or her lovely kitchen ware. So if you don't want to create WW3, it could pay to go buy some cheap stuff from The Wharehouse or similar.

The power supply I briefed apon above, has to be a DC supply. In other words, you need a Positive + and a negative - lead. The positive will connect to the component and the Negative will connect to the Cathode which is simply a flat piece of scrap alloy lying in the bottom of the tank. If at all possible, a current meter is awesome help. iot helps you maintain a constant current through out the process. As the Oxide biulds, the current drops away and the PS needs to be wound up to compensate. When you first switch on, the current will be very high and the PS will need to be low, or you will blow something. As the gas biulds, the current drops away quickly and you then need to wind up to maintain the current at a steady supply. If you use a Welder, you need to go to Tricky Dicky and buy a big mother Bridge Rectifier Diode or a couple of grunty single Diodes and put them in your supply so as you get DC. Some of those modern little Inverter welders are already DC and you can buy them quite cheap now. It is not essential, but a rule of thumb is 1A of current to every 1-2 sq centimetre area of component.

Next is where. The first essential you need is ventilation. Whether that be a Window or a fan, it needs to be good. The fumes that come off the Acid solution is choking and not good for you. You need to ensure that an open window does not allow access by some Kid or Cat or other small animal. The other concern is easy access around everything. You do not want to trip over something causing you to spill or fall into a tank.

Safety clothing is essential. You need eye protection. A splash with acid or Sodium hydroxide is not nice in the eye and could cause severe damage. A face mask is also helpful. The fumes are actually very fine droplets of acid in the air. Even with extraction, your head over a tank means you can still inhale the stuff and it is very choking. Gloves are essential. Don't even think for one moment you can cheat and get away without them. They need to be good chemical resistant gloves. Forget those cheap Nitrile or rubber disposable. Proper chem gloves are essential and they need to be long. Up to the elbows if possible. An apron is the next. A plastic or PVC one is what you need. it must be waterpoof and acid proof. No matter how careful you are, it is quite surprising how easy it is to get a small splash on clothes and you never knew till next time you wear it and find a hole clean through it. The important part though, is protecting you from an accidental spill.

If possible, have a hose nearby that you can wash yourself with lots of fresh water should something nasty happen. Battery Acid is at least fairly safe. It is not instantly burning and it does wash away quickly. But it does start to bite in a few seconds. Alkaline solutions of Sodium Hydroxide is a whole nother story. It bites like hell and it takes a fair amount of flushing to get the stuff off your skin. Never underestimate this stuff. I place it as a far more nasty substance than the Acid you are working with.

Just in case you happen to get pure Sulphuric Acid, be careful with that stuff. It is dangerous and you need to treat it with a lot of respect. I sugest the already mixed stuff from the Auto sparkies. But what ever, there is one rule to always obery. When diluting, you always mix A to Z. In direction of alphabet in other words. In our case, A to W, or Acid to water. Droping water into a high strength acid will often result in a bummer of a day.

Containers can be anything. Plastic of course. Well actually, they can be Lead, SST or Aluminium, but plastic tends to be cheap and easy to work with. Something with a lid is helpful. That keeps your fume problem in control. The container needs to be big enough and deep enough to be able to completely submerse the component.

When I anodised my Mast spreaders, the Acid bath was easy to make. A simply made a long wooden box and lined it with a heavy weight polythene plastic. But the hard part was how on earht I was going to Boil the components. I ended up using a long metal pipe standing on end. I welded a cap on one end and then dropped the component down the pipe once the water was boiling. A Gas cooker underneath was my heat source.

 

If you did want to explore colour. This is the range that can be covered. The advanatge of Anodized colour is that it is hard wearing and a finish you simply can not achieve with any form of paint coating.

 

Next installment I will go into the doing it

colors.jpg

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Pictures?? Do I get extra credits :wink:

 

Set ups can vary from a very simple plastic lunch box to very elaborate Lab type environments. What ever you set up, you have to ensure one important aspect throught out, and that is your safety. You will be using Electricity, Acid, Alkaline and Boiling water. And if you are like me, the more dangerouse thing you may have to deal with, is the wife! Especially if you use the Kitchen to boil the water, or her pots, pans and other utensils. All these process will pretty much ruin the looks or her lovely kitchen ware. So if you don't want to create WW3, it could pay to go buy some cheap stuff from The Wharehouse or similar.

The power supply I briefed apon above, has to be a DC supply. In other words, you need a Positive + and a negative - lead. The positive will connect to the component and the Negative will connect to the Cathode which is simply a flat piece of scrap alloy lying in the bottom of the tank. If at all possible, a current meter is awesome help. iot helps you maintain a constant current through out the process. As the Oxide biulds, the current drops away and the PS needs to be wound up to compensate. When you first switch on, the current will be very high and the PS will need to be low, or you will blow something. As the gas biulds, the current drops away quickly and you then need to wind up to maintain the current at a steady supply. If you use a Welder, you need to go to Tricky Dicky and buy a big mother Bridge Rectifier Diode or a couple of grunty single Diodes and put them in your supply so as you get DC. Some of those modern little Inverter welders are already DC and you can buy them quite cheap now. It is not essential, but a rule of thumb is 1A of current to every 1-2 sq centimetre area of component.

Next is where. The first essential you need is ventilation. Whether that be a Window or a fan, it needs to be good. The fumes that come off the Acid solution is choking and not good for you. You need to ensure that an open window does not allow access by some Kid or Cat or other small animal. The other concern is easy access around everything. You do not want to trip over something causing you to spill or fall into a tank.

Safety clothing is essential. You need eye protection. A splash with acid or Sodium hydroxide is not nice in the eye and could cause severe damage. A face mask is also helpful. The fumes are actually very fine droplets of acid in the air. Even with extraction, your head over a tank means you can still inhale the stuff and it is very choking. Gloves are essential. Don't even think for one moment you can cheat and get away without them. They need to be good chemical resistant gloves. Forget those cheap Nitrile or rubber disposable. Proper chem gloves are essential and they need to be long. Up to the elbows if possible. An apron is the next. A plastic or PVC one is what you need. it must be waterpoof and acid proof. No matter how careful you are, it is quite surprising how easy it is to get a small splash on clothes and you never knew till next time you wear it and find a hole clean through it. The important part though, is protecting you from an accidental spill.

If possible, have a hose nearby that you can wash yourself with lots of fresh water should something nasty happen. Battery Acid is at least fairly safe. It is not instantly burning and it does wash away quickly. But it does start to bite in a few seconds. Alkaline solutions of Sodium Hydroxide is a whole nother story. It bites like hell and it takes a fair amount of flushing to get the stuff off your skin. Never underestimate this stuff. I place it as a far more nasty substance than the Acid you are working with.

Just in case you happen to get pure Sulphuric Acid, be careful with that stuff. It is dangerous and you need to treat it with a lot of respect. I sugest the already mixed stuff from the Auto sparkies. But what ever, there is one rule to always obery. When diluting, you always mix A to Z. In direction of alphabet in other words. In our case, A to W, or Acid to water. Droping water into a high strength acid will often result in a bummer of a day.

Containers can be anything. Plastic of course. Well actually, they can be Lead, SST or Aluminium, but plastic tends to be cheap and easy to work with. Something with a lid is helpful. That keeps your fume problem in control. The container needs to be big enough and deep enough to be able to completely submerse the component.

When I anodised my Mast spreaders, the Acid bath was easy to make. A simply made a long wooden box and lined it with a heavy weight polythene plastic. But the hard part was how on earht I was going to Boil the components. I ended up using a long metal pipe standing on end. I welded a cap on one end and then dropped the component down the pipe once the water was boiling. A Gas cooker underneath was my heat source.

 

If you did want to explore colour. This is the range that can be covered. The advanatge of Anodized colour is that it is hard wearing and a finish you simply can not achieve with any form of paint coating.

 

Next installment I will go into the doing it

 

 

Nice stuff! why is it so hard to get these colors wheels? I have always liked the Bright blue colour but so many Anodisers will not do it.

 

 

Also? Do the local rossers think your running a p lab doing all this? :wtf: :lol:

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The colours are all heavy metals like Chromium which creates Green. Very expensive to buy if you can buy them. But also very toxic in this liquid form and difficult to dispose of the residues. You can't just tip them down the drain. The sealing is done slightly differently aslo, using some chemical which I currently forget the name. Something Acetate. So once again, another nasty which is in a tank of boiling water. For me and the very small amoutn I did, it just wasn't worth the hassles. If someone wants to look into that, there is heaps of info on the net about it all. It's easy enough to actually carry out the process. I did try a dye myself once, just to see if it would work. But ordinary dies don't seem to. I believe they have to be an Ionic compound, but never really investigated further. This is another reason why colours are limited in range. Their is really only that lot in the pic.

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