Anodising

[Julian M]

Hello everyone!

I run my own small engineering company in hertfordshire england. Most of the parts we machine are out of aluminium and the majority of these parts are black/red/clear anodised. We decided for this reason to get our own anodising equipment. The equipment has just been installed and i was wondering if anyone out there would be kind enough to share some pearls of wisdom. We will receive training from our equipment supplier but any other help would be gratefully received ie jigging up,safety etc

Julian

[chola]

Hi Julian,

Well seeing as no one else has had a go I'll chime in....

Firstly I don't know much about anodizing (in fact I cheat and spray paint alloy parts in clear tinted paints! but I'm only after the look not the hard wearing properties), but I actually found some very good links on this site.

www.mini-lathe.com

Try here http://www.mini-lathe.com/Anodizing/...g_aluminum.htm

Hope this helps, there is some very funky stuff on there, can;t remember exactly which one but one has some parts that have been anodized a few different colours!

Colin

[Julian M]

Originally Posted by chola Hi Julian, Well seeing as no one else has had a go I'll chime in.... Firstly I don't know much about anodizing (in fact I cheat and spray paint alloy parts in clear tinted paints! but I'm only after the look not the hard wearing properties), but I actually found some very good links on this site. www.mini-lathe.com Try here http://www.mini-lathe.com/Anodizing/...g_aluminum.htm Hope this helps, there is some very funky stuff on there, can;t remember exactly which one but one has some parts that have been anodized a few different colours! Colin

Thanks for this colin, i had a look on ron newman's site which is very good. Theres an anodising guide on there for $25 which i might get. What i need now is a UK based supplier of all the chemicals and dyes. Endless hours on the internet no doubt. Thanks again

Julian

[chola]

Hi julian,

Glad to be of some assistance.

I've also heard / read somwhere that plain old food colouring can be used as a dye! You know, the type people use to colour the icing on cakes and stuff! Very inexpensive as well, but I cannot vouch for this, again having not done any anodizing.

Could the people supplying you with all the hardware not provide the dyes or at least some contacts for this stuff? Maybe try Ebay for the dyes??? Just a thought - you may find a supplier local to you on there.

As far as the safety aspect goes, I think (again from the research I've done), that just general good safety practices are in order (the usual things like the cleanliness, use rubber gloves, eye protection, perhaps some kind of mask and good ventilation - you will find a lot of the safety info will be written on the containers that the various chemicals come in), the other key point I've picked up is to keep everything extremely clean (especially the actual parts to be anodized), so I would imagine a dedicated area would be an absolute must.

Again i've only read this information on other sites, but I'm sure you will come across this as well in your quest for more knowledge. I did a fair amount of research for a friend who owns an engineering shop over here in Australia and is looking to get into anodizing as well.

Thanks.

Colin

[Julian M]

Originally Posted by chola Hi julian, Glad to be of some assistance. I've also heard / read somwhere that plain old food colouring can be used as a dye! You know, the type people use to colour the icing on cakes and stuff! Very inexpensive as well, but I cannot vouch for this, again having not done any anodizing. Could the people supplying you with all the hardware not provide the dyes or at least some contacts for this stuff? Maybe try Ebay for the dyes??? Just a thought - you may find a supplier local to you on there. As far as the safety aspect goes, I think (again from the research I've done), that just general good safety practices are in order (the usual things like the cleanliness, use rubber gloves, eye protection, perhaps some kind of mask and good ventilation - you will find a lot of the safety info will be written on the containers that the various chemicals come in), the other key point I've picked up is to keep everything extremely clean (especially the actual parts to be anodized), so I would imagine a dedicated area would be an absolute must. Again i've only read this information on other sites, but I'm sure you will come across this as well in your quest for more knowledge. I did a fair amount of research for a friend who owns an engineering shop over here in Australia and is looking to get into anodizing as well. Thanks. Colin

Thanks for the info. The company that supplied and installed the equipment
also supplied and installed the chemicals we needed that is nitric acid, sulphuric acid , metal cleaning salts, caustic soda, black/red dye. However there customer service isnt great so we would like to find our own supplier, but this isnt easy. Ive found a place local to get causic soda, but the acids/dyes im waiting for a quote from a company in switzaland.

Apart from this the actual anodising is going really well. Ive attached some pictures for you to see. If your friend needs any practical advise please let me know i will try to help with my very limited knowledge.

Thanks again

Julian

[martinw]

Dear Julian,

I was looking into anodising a few years ago and stumbled on this MOD document...

http://www.metroplating.co.uk/pdf/DE...AN%2003-25.pdf

I also found a really, really good American website, but I can't find it right now. Sorry.

Best wishes

Martin

[Geof]

What do you have to do about waste treatment for the spent chemicals and the wash water that may be either strongly alkaline or acidic and contain metal salts?

I looked into setting up an anodising facility at our plant. We currently process about 1500 kg of aluminum parts through anodising per month and when our anodiser mentioned the possibility of being closed down I had a brief period of conniptions. Equipment needed to meet the waste treatment requirements in our area would cost as much or more than the installed cost of all the anodising equipment. Basically we would have to neutralize and treat everything so the water we discharged was virtually drinkable.

If you have not even looked into what is needed in your area I suggest you do just as a safeguard against unpleasant surprises.

Regarding the comment about food dyes yes they work. Years ago I was teaching a chemistry program to electronic engineering students and this was one of the laboratory experiments I developed; anodising and colouring with food dyes.

[Julian M]

Originally Posted by martinw Dear Julian, I was looking into anodising a few years ago and stumbled on this MOD document... http://www.metroplating.co.uk/pdf/DE...AN%2003-25.pdf I also found a really, really good American website, but I can't find it right now. Sorry. Best wishes Martin

thanks for this martin this document is very thorough as you would expect from the MOD. some useful information on ph testing of the seal, and jigging

[Julian M]

Originally Posted by Geof What do you have to do about waste treatment for the spent chemicals and the wash water that may be either strongly alkaline or acidic and contain metal salts? .

As far as spent chemicals are concerned we havent had to replace them yet. I probably should look into it thou, ready for when we renew our solutions. Thanks for the advice

Julian

[martinw]

Dear Julian,

There are other MOD Defence Standards which give loads of information.

There is a really good one Def Stan 03-2 on cleaning and preparation of metal surfaces. It's a "dry as dust" read, but stuffed with knowledge.

Other matters

1) try the website www.finishing.com

2) you can get chemicals at..

http://www.lpchemicals.com/

3) another link that may point you in the right direction as regards chemicals and other "stuff" is a list of laboratory supply companies

http://www.liv.ac.uk/Chemistry/Links/labsupplies.html

Best of luck

Martin

[chola]

Hi Julian,

Nice pics, very professional looking set-up. Thanks for the offer of info for my friend as well, I will pass it along to him.

The disposal of spent chemicals can be a bit of a concern at times, however also consider that there may just be a company around your area that specialises in just that, similar to the guys that pick up and dispose of acids, used oils and brake fluids for the automotive industry...your mechanic has to get rid of the stuff somehow!

Good luck with it all and please post some more pics when you get a bit done. Even a nice little 'how-to' would make for good reading.

Colin

[Julian M]

Originally Posted by chola Hi Julian, Even a nice little 'how-to' would make for good reading. Colin

Hi Colin

Heres a 'how to' using my limited knowledge.

Firstly:Jigging is a really important part of the process. Simply to hook a length of aluminium wire thro a hole in the part to be anodised is generally not enough. The reason for this is that the anodised layer that is formed on the part is an insulator, this layer forms between the part and the wire and breaks the connection between the two. You can however use wire successfully if you force the wire into the hole tightly, or bend the wire thro 2 holes in the part in such a way to create a spring loaded effect. Both methods prevent an anodised layer being formed between the wire and part.
A prefered method of jigging is to use an ally bolt in a thread its 100% reliable.


Cleaning the part: The first tank is heated to 40degrees celcius, and contains aluminium cleaning salts(minco cleaner) and water. There is also about 14volts running thro it. The part is dipped into this to form the anode connection and left for about 3-5minutes. This process chemically scrubs the surface (the part fizzes which is good to watch). After this the part should be 'chemically clean'

Rinse in clean water tank: If there are no water breaks you know its clean.

Etch Tank: contains caustic soda solid and water at room temp. This process is optional it gives the part a matt finish and is good for giving a uniform surface finish to the part. Leave part here for about 3-5minutes depending on size of part. This solution basically eats away at the part so if you leave it too long it will disappear!! Etch can also be used to strip preanodised parts.
After this rinse tank again

Desmutt tank: Contains nitric acid and water at room temp. This tanks removes smutt created by etch tank. 3-5minutes. Rinse tank again.

Anodising tank: Contains 10% sulphuric acid and water at room temp. Connected to the rectifier set at 12-18volts. The part becomes the anode and is left for 20-40 minutes. The longer you leave it the better the dye will take to the part if required. The tank is air agitated using an oil free compressor. Agitation keeps the solution's temp down, and keeps it moving. During the anodising process the surface of the ally is converted into anodise
a byproduct of this is a dark gas which can effect the surface finish on the part so the air agitation moves this gas away.
Rinse tank again.

Dye tank if required: Powder form dye in water. Heated to 60deg celcius. Leave part in for about 20minutes. The anodised layer is porous so will absorb dyes

Hot seal: water heated to 80deg celcius. Leave part for 20minutes. This process closes the pores of the anodised layer thus sealing in the dye and making the layer harder.

Its quite good fun really, a nice change from engineering!

julian