Anodising

[Gordon WParticipant @gordonw]

I’m no expert in alloy cleansing, many years ago, trying to clean old castor oil off a BSA Gold Star rocker cover with hot caustic soda left it to long, no rocker cover. I found by accident that washing powder ( the stuff that goes in washing machine) in hot water is a good cleaner for ally, have boiled up and recovered a 50 yr. old carb. recently. Also cleaned a silver soldered brass boiler and a S/S silver soldered displacer, very effective. This stuff is hard on the skin and of course wash afterwards. Hope this might be of use.

[David Clark 13Participant @davidclark13]

Hi There

Check out the digital free copy of Model Engineers’ Workshop.

It has a good article on anodising.

regards david

 

[Ramon WilsonParticipant @ramonwilson3]

Thanks David, Another good article. I think it fair to say I’m now well versed in what to do with all the super help and advice I have recieved. The parts are underway and I hope to be setting up to have a go next week – weather permitting that is!

 

Regards – Ramon

 

 

[ZigFireParticipant @zigfire]

Hi Ramon,

Just one thin I meant to mention, no matter what anodising process you use, the result will ONLY be as good as the finish on the original parts. Anodising will not “cover up” any poor surface finishes. The better the surface finish the better the anodising result.

Cheers

Michael

[Ramon WilsonParticipant @ramonwilson3]

Thanks Michael, Yes I was aware of that – I’m taking care not to get any of the parts so far made scratched or dinged. Nearly there, just the cyinder fins to do today.

 

regards – Ramon

[thomas oliver 2Participant @thomasoliver2]

Try this site for info.on anodising – it is about 33 pages to download, and is commercial but covers the subject adequately. — http://www.focuser.com/atm/anodise/anodise.html

[Ramon WilsonParticipant @ramonwilson3]

Hi again,

 

I now have some results – not great – but  at least something to report.

First off though I’d just like to say thanks to all of you who have responded so far, your input is much appreciated.

 

I finally cobbled together the neccessary items to have a go at this process and have jury rigged a set up using a 20 volt power supply that was made years ago to drive the cross slide milling spindle motor. Control was via a Variac on the input side and a test meter ut in circuit to measure the current. A spot of ‘alchemy’ provided dyes – two greens from Dylon cold water dyes and two from disolving whole tubes of artists water colour into about 300mls each.

 

 

The tank was filled with acid that was mixed several years ago as a pickle though never used. It appears very ‘clean’. Having thought about it I’m sure I mixed this with clean rain water.

 

The cathode is a lead strip about 75mm wide and runs down the side, across the bottom and half way up the other side.

 

The hanging wires are from 1.5 mm ally welding wires bent back on itself and pushed a tight fit into a hole drilled into the test pieces (these were parted off from the stock the cylinder heads were made from – probably HE30 though not certain.

 

The first test piece was cleaned in cellulose thinner dried off then washed in the cold (room temperature) washing soda degreaser.  20 mins or so produce a rather striated effect which I put down to poor degreasing. It did however have a different ‘feel’ to it rubbing it across some wet and dry on a flat surface. It would not however take any colur. After ringing someone I knew who had some experience with anodising I was told to make sure the soda degreaser was hot and to increase the current and time to about 40 – 60 mins. His experiences weren’t very encouraging regarding the colouring however as he had had a similar lack of take up. What he had been able to get to take albeit poor colour though had been acheived by an increase in amperage.

 

The second piece was left in for 50 mins and the current increased. This resulted in a much better part – a smooth and uniform nice grey finish. Dissappointment then to find despite an hour in the dye not so much as a speck of colour anywhere. I mixed up the violet dye as I have read that greens can be difficult but no luck there either.

 

These are the second (left) after treatment and the third part before 

 

I decide then to do as Bernie had suggested and use a 12volt battery to get a much higher current. Left in the same amount of time this did not come out any near as evenly coated as the second and as you can see left a deep pitted hole near the hanging wire.

Despite the much higher current this did not take up any dye either.

 

 

 

The second part will not pass a current across the surface. The third will in areas – passing the test probe over the surface leads to intermittent connection.

 

My thoughts so far are that the current needs to be increased lightly more than the first set up can give. The time could be slightly longer perhaps. The biggest area for improvement has to be the connection between the hanging wires and the parts as I think that the area of contact is too small and probably reduces throughout the process.

 

I’ve bitten the bullet and ordered a decent supply unit which is something that’s been needed for some time but always got by without.

I’m perplexed by the lack of dye take up at this time but quite impressed by the surface finish on the second piece. I will try inks next and wonder if solvent based dyes would work too

 

If anyone has any furth <

[Ramon WilsonParticipant @ramonwilson3]

 

 

If anyone has any further thoughts to help overcome this problem then I’d be pleased to hear from them.

 

Hope this of interest – it’s certainly taken my mind off machining for a while!

Regards for now – Ramon

[Dave MartinParticipant @davemartin29320]

Ramon,

 

From a quick look/read here, areas I would definitely look at are (a) anodising electrolyte make up and control, (b) ano tank temperature control, (c) current density & control, (d) electrical contact, and (e) using proper dyes.

 

You may find it worth looking at some notes on anodising I posted elsewhere

 

Ti rods can be one of the best methods of making and maintaining contact.

 

Dyes – there are some who swear by clothing dyes and many more who swear at them! (especially their un-reliability)  You will find a small investment in proper anodising dye takes a major unreliability away. You have to remember you’re trying to get the dye molecules down into the honeycomb matrix – so if either (i) the matrix is too fine (ano’ed at too cool a tempeature) or (ii) you have dye moleules that are too big, you won’t get much/any dye in there.

 

Dave

Edited By Dave Martin on 04/05/2010 17:03:09

[Ramon WilsonParticipant @ramonwilson3]

 

Thanks for this Dave.

 

I have printed off your info and have read it through several times. I have several other articles some quite old but yours is much the best description so far.

 

Though I’m fairly happy with the ‘cleanliness’ of the electrolyte – I’m confident it is unadulterated, though it is not mixed with distilled water – it’s obviously too weak – possibly 10 to 1 so this will be improved.

 

Temperature, well that was well down on your recommendation I guess – really cold outside and as you see this was carried out by the door with a fan blowing the fumes away. Would an aquarium heater be of use?

 

The PSU  I have ordered has a current control facility up to 2.5A so given that I only intend to do relatively small parts I’m hoping this will be adequate.

 

I have a small piece of Ti sheet so will try to get a few strips out of it and make up some ally screws

 

The dyes? well as you say all I have read points to hit and miss using clothing dye. As I would like to make a good job of this I shall definitely get the right thing before the next attempt. I certainly won’t have another go until I feel I have all the parameters in the right order!

 

A few questions-

 

What is in the ‘de-smut’ bath? and does this need to be at  higher temperature than room temp?

I see you recommend washing/rinsing in DI water though other articles recommend washing under running water – presumably that’s tap water. Is that likely to have a negative effect? The black container in the pic was filled with rain water the parts well swirled around in it to wash – again is that likely to spoil matters?

 

Finally would aeration from a small aquarium pump be suitable for agitating the acid?

 

Many thanks again and for those possibly expecting something a bit more positive in the results don’t go far – “I’ll be back”

 

Regards – Ramon

[TerrydParticipant @terryd72465]

Of course washing soda can defat but not as much as Caustic soda of course but I assume most users will at least adhere to the normal housewife’s safety standards and  wear rubber (in my case nitrile) gloves.  But then again my gran used washing soda all her life for many purposes and still lived to a good old age.  I’m not so sure she would have had the same luck using the caustic version so much 

 

Terry

[TerrydParticipant @terryd72465]

Hi Dave and Ramon,

 

You are right about the dye problem,  The only dye I have seen reported as working is one  of the older Dylon types others do not work as far as I know.  however the cost of ‘proper’ anodising dyes, inexpensive as they may seem, is prohibitive for very small scale or one off pieces.

 

A good essay on this is in this guy’s experiments (and photographic proof):

 

http://astro.neutral.org/anodise_dye.shtml

 

Here is a quote from this site:-

“The only clothes dye that I have found that works is Dylon Multi-Purpose dye. Other Dylon brands do NOT work. I guess the dye particles are not small enough. Dyes that do not work include the Dylon COLD range and the dylon PURE COLOUR range.”

 

Probably those who swore at the dyes Dave, were using the wrong ones?

 

So Ramon, it may be the type of dye you are using as well as the other factors suggested.  The site above is well worth investigating even if it is a covered with annoying adverts, you can navigate around those  .

I’m not sure if Dylon make these types of dye (Multi-Purpose) any more so it may be worth stocking up if you find a supply at the back of some old haberdashery  store  .

Terry

Edited By Terryd on 04/05/2010 22:19:53

[VersabossParticipant @versaboss]

Hmm, it seems no one mentioned the fact that some aluminium alloys are ‘not suitable for anodising’. I don’t know what HE30 is and if it is ok or not, but know for certain that I can’t use all the alloys my supplier has if the parts have to be anodised later. I suppose  this means also that they can’t be coloured.

Checking the descriptions in my catalogue, I find the following alloys recommended for anodising:

AlMgSi1, AlMgSi0,5

AlMgSiPb

AlMgç,5Mn0,7

Unsuitable or bad are:

AlCuMgPb

AlCuBiPb

For some alloys I see no recommendations. It seems the alloys with copper are the bad ones.

I hope that this is of some help

Greetings, Hansrudolf

[TerrydParticipant @terryd72465]

Hi Ramon,

 

I just noticed from your post that you used Dylon cold water dyes.  These are the ones that apparently don’t work.  Here is a link which I posted before that may help,

 

http://astro.neutral.org/anodise_dye.shtml

 

Best regards

 

Terry

[TerrydParticipant @terryd72465]

Hi again Ramon,

 

Sorry about the multiple posts but you might like to look at the proper dyes available here for not too extortionate a price:

 

http://cgi.ebay.co.uk/Anodise-Dye-30ml-Concentrate-Anodising-Anodizing-/110528094928?cmd=ViewItem&pt=LH_DefaultDomain_3&hash=item19bbfce2d0

Regards,

Terry

[Ramon WilsonParticipant @ramonwilson3]

Hi Terry thanks for these links. Had seen them before – have looked at so many on the subject and on dyes but have forgot to bookmark most () so this was a timely reminder.

 

The power unit from Maplins has arrived and I have ordered some dye from the link above to see if that improves matters. If that doesn’t work then I will try some of the Carswells stuff and if that doesn’t work then It’s going to remain ‘au naturel’ !!!.

At this rate it would have been cheaper to visit the guy up the road but then I suppose all I would have is two or three green bits to show for the outlay.

 

Managed to get my little old Burgess band saw to wend its way through this piece of Ti sheet tonight. Lain under the bench untouched for years it’s about 2mm thick and isn’t it bloody tough!

 

Hansrudolph- I have checked out HE30 – it appears this is a discontinued spec and it is now listed as ‘6082’. The anodising properties are given as good. I was aware that not all alloys will take hence test pieces cut off the stock the parts were made from but thank you for your thoughts on this.

 

It’s a ‘holiday’ week this week so time is a bit limited – I keep sneaking in the workshop but not for long

 

Regards for now – Ramon

 

 

[TerrydParticipant @terryd72465]

Hi Ramon,

 

At least you will have the experience and some expertise i anodising and have the kit to do more in future, which would not be the case had you visited the ‘guy up the road’.  At very least you have something to sell if needs be.

 

I have every confidence in your success

Best regards

Terry

[Ramon WilsonParticipant @ramonwilson3]

Hi again,

 

Had another go today with the new set up but still using the original acid in the ano tank. This time the tank is placed in a larger one filled with water which is heated with an aquarium heater (24 C). The ano tank has an ‘agitator’ made from an ali tube drilled with smallholes and fed by a small aquarium air pump and the test piece was suspended on a piece of titanium strip. A milli-ampmeter really needs to be in circuit as the amp meter on the unit is too ‘coarse’ to get a reading on – back to the test meter then though if the parts get larger or the part count goes up then the current will need to increase relative to the surface area

 

A 50 min dose at 15 volts followed by a lengthy soak in the dye (I confess I forgot about it for an hour or more) – correct anodising dye that is, from the ebay link you posted Terry – saw this result.

 

Not anything to write home about I agree and nowhere near as good as hoped for but you have to agree it is green   At this stage it has not been sealed in a steam bath and is much shinier than the pic suggests but importantly, no, it doesn’t rub off  

 

The dye is a very drab green. This is from the correct dilution though I did keep a small amount at twice the strength but it’s not really the shade wanted. However it is helping to show that the system is working. The more ‘correct’ (and more expensive) green can be got later.  I intend to change the acid out for 4 to 1 for the next attempt and see if that improves matters.

 

Assembly of the ‘Racers’ is now awaiting a successful outcome of this – I’ll keep you posted.

 

Regards – Ramon 

 

Edited By Ramon Wilson on 14/05/2010 23:11:07

[TerrydParticipant @terryd72465]

Hi Ramon,

 

 it’s good to see some progress.  It may be a mucky green but at least you now know that your process works and the only major problem is the dye colour.  I think that’s the real achievement, that you made the process work.

 

Glad to be of help with the link.

 

Well done 

 

Terry (with admiration)

[Ian S CParticipant @iansc]

Just been doing some reading up, if you can’t get the dye to take increase the currentthat increases the size of the pores in the surface alowing penetration of the dye. Ian S C

[Ramon WilsonParticipant @ramonwilson3]

Thanks Ian,

 

Yes from what I have read too that and an increase in di-electric strength is what is probably required. I shall do one step at a time – acid strength first then increase the amperage.

 

Electrics are not my strong point I’m afraid – I do know how to wire a plug – that kind but I think I’m learning

 

I noticed however that to increase the current that the volts needed to increase – the ammeter on the unit not registering such a small amount. There are varying recommendations from 3 to 6 amps a square foot – the part shown worked out to 27 milliamps though it was not possible to check the actual current on this one.

 

It’s a garden day today but I hope to get back on to it tomorrow – thanks again

 

Regards – Ramon

 

Edited By Ramon Wilson on 15/05/2010 13:40:34

[Les Jones 1Participant @lesjones1]

Hi Ramon,

                    I seem to remember in the distant past reading that to get the anodising thick the voltage had to be increased during the process. This is because the anodising is a partial insulator so as it builds up the voltage required needs to be increased to keep the current constant. You should be able to verify this by watching the current as the anodising progresses. If it decreases (With the voltage constant.) then my memory is correct. If it does not decrease I must be talking rubbish.

Les. 

[Ian S CParticipant @iansc]

One thing that increases current is to move the electrodes closer, and or enlarge it. Hook up an ammeter in the line, and have good heavy cables- if they start to get warm a bit more copper won’t hurt, just don’t over load the power supply, I,v done that. Ian S C

[Ramon WilsonParticipant @ramonwilson3]

Thanks Ian and Les for your continuing input.

I have had a little further success today which bears relation to your suggestions.

I began as said by changing the electrolyte. The 4 to1 that I had in store was not quite enough so had to add some of the 10 to 1 – at a rough calculation it worked out about 6 to 1 so I added a bit more neat acid and this new mix appears to have done the trick.
I also added the test meter in circuit and this was a big improvement in being able to monitor the current . I noticed this did not drop at all as the time increased though this did happen on that initial jury rig set up. I think that this is probably due to the better and constant contact of the Ti hanger strip as opposed to the ali ones used previously which were obviously anodising at the same rate and probably reducing the contact area.

 

The second test then was at 12 volts and a consistent 30 ma for a 50min duration. Using the ano dye as for the previous test the take up of colour began immediately though quite faint,  the result below (centre piece) was after 20 mins in ‘hand hot’ dye – a much better colour take up and nowhere near as drab as expected.

 

The third piece on the right was done exactly the same but was dipped into Parker green ink. The take up of colour was virtually instantaneous and the result you see was no more than five seconds exposure! I sealed this one in steam but notice this has caused very faint blotching however the parts look much better ‘in the hand’ than the pics allude to.

I must admit that despite the green actually being closer to a blue I was really surprised with the colour absorbtion of the ink. This was neat ink and I think perhaps too strong so will try diluting it and see if a longer soak provides a more deeper and uniform finish.

 

The big thing is that the process now appears to be working quite well and just needs tweaking. I shall do several more test pieces to be certain before any of the Racer parts but must admit with the bottom ends of them all assembled I’m itching to get the tops done and try them out – “ahh patience laddie”

 

Regards for now – Ramon

[Ramon WilsonParticipant @ramonwilson3]

Hi again,

 

Well after a few more test pieces I finally bit the bullet and did what I set out to do and have to say am very pleased with the results.

 

I did the smaller ‘DC Rapier’ head first using the initial green dye from Terry’s ebay link. As you can see the previous test piece gave a different hue. I think this was due to when transfering the dye into a glass jar I noticed there was quite a bit of sediment in the bottom of the bottle so gave it a real good shake. Typically the shade of the test piece is more the shade I was after however the finished item looks okay in situ on it’s crankcase.

 

The cylinder off the Racer was done in ‘Parker’ green ink and has this lovely bluey green shade. However despite using the same current and very careful timing both in the ano bath and the dye the second cylinder came out a lighter shade. It was put back in the dye for a further 15 mins but no increase in colour occured. I’m surmising that this is due to the gradual depletion of the dye as each part is done. Though it did not occur to do so at the time, the amount of dye available was insufficient to do two parts at once but that is how I would do it the next time if I wanted to get two parts or more the same shade.

 

Whatever I have had an enjoyable time learning how to carry out this process and it has added another dimension to the making of small I/C motors and bodes well for the future. That OPS marine can now finally have a red head!

 

I would like to thank all who posted on this thread either in reply to my questions or to ensure I was armed with the right information. Your input has not only kept me motivated but ensured a safe and successful outcome. Thanks indeed.

 

Tomorrow then sees the final assembly of the Racers and hopefully a test run (or two!)

 

Regards – Ramon

 

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