# Hard anodizing at home?



## nima (Jun 12, 2006)

I was thinking about experimenting with hard anodizing, however, there's very little information on the net. Theres enough on Type II anodizing, but almost none on HAIII. So far, it seems to me that the only differance is that hard anodizing uses a chilled sulfuric acid bath, while Type II is done at room temperature.

Also, how do you mask off parts, like threads, when anodizing? And how do you dispose of spent sulfuric acid? Is it safe to pour down the drain? What plastics are capable of containing sulfuric acid during the process, or do I have to use glass?

Thanks a lot,
Nima


----------



## Protaeus (Jun 12, 2006)

Not sure about anodizing, but I am pretty sure that sulphuric acid needs to be contained in a glass container. Plastic will most definately not cut it. Also, I do not believe that it is safe to pour down the sink. I'd ask the place you bought it from how to get rid of it properly.


----------



## TinderBox (UK) (Jun 12, 2006)

I suppose you need a ph meter and some alkaline to netralise the acid then it should be safe to pour away, unless their are other by products.

regards.


----------



## tebore (Jun 12, 2006)

Just dump tonnes of baking soda in the acid when you're done. Just like a Gr4 science volcano.


----------



## markus_i (Jun 12, 2006)

Regarding HA - no idea. All I've read suggest to keep the temperature down - and as a result of that, increase the voltage.

Regarding the sulfuric acid: for one thing, the acid isn't spend when anodizing, so you can keep on using it. As a container, most common kitchen plastics will do - after all, car batteries are filled with the stuff, and the last time I looked (admittedly a few years ago) they were all made from plastic.

If you have to get rid of used acid, either 
- thin it. With a lot of water. And I mean a lot. Really a lot. Like a bathtub full per small glass of acid. Or, much better, 
- neutralize it. Any alkaline stuff should do in a pinch - basically anything between drain cleaner and baking soda, including dishwasher detergent. Just prepare a solution of your alkali and ___slllooowwwwlllyyyy___ mix it with the acid, in a well ventilated area. Stir well. Occasionally, test the acidity e.g. with a piece of litmus paper. Unless either the acid or the alkali contained any heavy metals (which usually won't be the case if you've used the acid only for anodising - and you'll see it when you're neutralizing), the result should be ok for simply pouring away. Or
- bring it somewhere where it can be properly discarded. Don't know about your country, so have a look around. But essentially any place you can buy the stuff should be able at least to tell you how to get rid of it.

Bye
Markus


----------



## dulridge (Jun 12, 2006)

markus_i said:


> If you have to get rid of used acid, either
> - thin it. With a lot of water. And I mean a lot. Really a lot. Like a bathtub full per small glass of acid.



Sulphuric acid used in anodising is fairly high concentration stuff as I remember - over 50%. If you don't already know how to handle this stuff don't mess with it - you will, at best get some very nasty burns. Strong sulphuric acid will kill you if it gets a chance. Anywhere where the stuff is handled in any quantity should (by law) have a drench shower in order to safely wash the stuff off you. A drench shower makes a firehose look extremely wimpy. If you don't have one - don't handle concentrated sulphuric acid in more than teaspoon amounts.

And never, never, never add water to strong acid. Unless you enjoy the resultant explosion and boiling acid everywhere. This can, and has, killed people. This complicates the issue as you have to handle the acid a fair bit as you can only dilute small amounts at a time. 

And your loacl sewer authority is going to be very deeply unhappy with you - people can be prosecuted for putting nasty stuff in the sewers. I once worked in a lab testing the evidence. Unless very, very well diluted it will not do any favours for your drains.



markus_i said:


> Or, much better,
> - neutralize it. Any alkaline stuff should do in a pinch - basically anything between drain cleaner and baking soda, including dishwasher detergent. Just prepare a solution of your alkali and ___slllooowwwwlllyyyy___ mix it with the acid, in a well ventilated area. Stir well.



*This will kill you. Don't.*

Acid to alkali and remember that considerable amounts of heat will be released therefore stuff is going to boil. Even more heat than the considerable energy of hydration of sulphuric acid as you also have the energy pumped in by neutralisation.



markus_i said:


> Or
> - bring it somewhere where it can be properly discarded. Don't know about your country, so have a look around. But essentially any place you can buy the stuff should be able at least to tell you how to get rid of it.



Making sure the container doesn't leak. 

If you don't know what you are handling don't even think about home anodising. As I remember you are also going to need a large rectified power supply - the only time I anodised anything was about 35 years ago in school and the power supply was basically a large welding set with a rectifier.

Nickel, monel metal (a pretty inert nickel alloy), platinum or lead containers are safe enough though I'd replace the lead ones quite often. Lab sinks ued to be made from lead.

A well sealed ceramic sink will handle most nasties but make very, very sure that it is completely dry first.


----------



## PhotonFanatic (Jun 12, 2006)

In addition to the excellent warnings already posted, I'd just like to add that sulphuric acid fumes from anodizing are nasty to anything metallic in your house. So you better have an excellent ventilation system in place, or kiss your fine equipment goodbye!

Now a separate building with ventilation, etc., that might be OK, at least as far as avoiding damage to anything other than your anodizing equipment.


----------



## PEU (Jun 12, 2006)

in a nutshell: don't worth the hassle. 

Even if you manage to be safe based on the previous posted warnings you will need to cool the bath to near 0 degrees celcius and carefully control the current increments of the parts being hard anodized. 

If you pump too much current the part will be ruined in almost no time, look what happened to a commercial shop when they misscalculated the current flowing thru a test NEOCA BL set:







it makes a nice sharpening tool  


Pablo


----------



## jar3ds (Jun 12, 2006)

lol... now we'll have CPF members going into abandoned farm houses to HAIII...

the police will show up thinking its a meth lab


----------



## greenLED (Jun 12, 2006)

markus_i said:


> If you have to get rid of used acid, either
> - thin it. With a lot of water. And I mean a lot. Really a lot. Like a bathtub full per small glass of acid.


(undeline mine):huh2:


****Warning!!!***

 **Do not add water to acid!! The resulting reaction can be explosive. The faster you add the water, the more violent the reaction.*​ * 
Unless you have the proper knowledge, experience, and safety equipment, DO NOT play with dangerous chemicals at home (and take advise from an on-line forum with 2 teaspoons of salt). Stay safe.


*

 As a final note, you can add water to acid, but you need to do it **slooooooowly*** and ***always*** wear proper safety gear, and handle chemicals inside a dedicated fume hood. I do not endorse the use of chemical reagents outside a dedicated lab. *
*


----------



## Galiphrey (Jun 12, 2006)

dulridge said:


> ...have a drench shower in order to safely wash the stuff off you. A drench shower makes a firehose look extremely wimpy....
> 
> And never, never, never add water to strong acid. Unless you enjoy the resultant explosion and boiling acid everywhere...



Hi; just curious--does a drench shower supply water? Is that safe if you have spilled strong acid on you? <I don't know anything about it, but was just curious...>


----------



## dulridge (Jun 12, 2006)

Drench showers

Yes they supply water. A LOT of water. Think 6" water main with a really good head behind it. The idea is to flood acid on you away as fast as possible. The force of the water is painful - I've been hit by firehoses and they don't even come close. You will be spending some considerable time cleaning up afterwards, believe me.

What it is doing is removing the nasties from your person as fast as possible. 

While hydration of concentrated sulphuric acid releases considerable quantities of heat, there is sufficient of a flood to cool it as well as remove it quickly. As in when a vessel of boiling chromic acid (mixture of concentrated sulphuric acid and postassium dichromate - carcinongenic, boiling point 300 centigrade) decides to throw some at you. Reflux condenser decided to break at an inopportune moment throwing the contents at me. Oh yes, and the substance in the vessel being violently oxidised was raw sewage...

A small amount (5-10ml) of nasty hit my face and was trickling down my forehead. More hit me in the chest.

Hesitate and you have no face any more - that has to come off in a hurry. You need to apply a very large amount of water very, very fast. Much of my clothing disintegrated rather quickly, much to the amusement of everyone else in the lab. They were less amused at the effort it took to dry the lab out afterwards.

That was 20 years ago when chemists were real chemists - none of this wimpy analytical machinery - we did everything the hard way - which means using fair-sized samples though far, far smaller than in my uncle's day. He'd say give me a couple of pounds of anything and I'll tell you all about it. In my day a few tens of grammes would do. But I digress in a major manner.


----------



## nima (Jun 12, 2006)

First of all, thanks for all the quick replys, I really wasn't expecting this many, this quickly.

As far as safety is concerned, I have handled dangerous chemicals many times before, and I am moderatly confident in my ability to experiment with sulfuric acid and live to experiment again. I have read the MSDS several times over, and I am familiar enough with the chemical to handle it. GreenLED, I am familiar with the old saying, "Do as you oughta', pour acid into watta'." As far as disposal, I think I am going to slowly pour it into a bucket of ice water, possibly with baking soda diluted in, then slowly pour that down the drain, with cold water running. As my supplier is my local grocery store, they are not going to have any idea how to dispose of it.

For maintaining 0 degrees, I think a double-boiler design with ice water in the lower half should suffice. Controlling current is a problem I have yet to solve. I don't have access to a lab power supply capable of the necessary amperage. Perhaps a computer power supply, a large variable resistor, and an ammeter? I could just use a low current, and leave it in the for a long time. It seems that thickness is dependant on voltage and time, and speed is dependant upon current. I still have no idea how to mask parts off, but it seems that soldering on lead would work, if no easier method surfaces. Also, I won't be able to obtain a concentration greater than 50 percent, because my source only sells 35%. I don't think this will be a problem, though.

Bear in mind that this is an experiment, and the primary purpose is to gain experiance and knowlege doing something you enjoy, rather than get a nice coating. A coating shop would probably be cheaper, and serve the latter purpose better.

PEU, I think this might be what happened to your light. Kind of a cool effect, possibly a target for a future experiment.


Thanks for the help,
Nima


----------



## dulridge (Jun 12, 2006)

Data sheets are not experience... We are talking about stuff that can kill. Bear that in mind. 

There are significant problems in controlling temperature - just look at any lab supplier's catalogue to see how expensive these are. Then divide by 6-50 for home built equivalents.

But consider just how large the quantities of substances are going to be - and remember that heat output goes up by the cube of volume - surface area (i.e. heat loss) goes up by the square. All that energy has to go somewhere. You do not wish it to go into you. It will if it can (Murphy's Law). There is no way that double boiler solutions will cool it adequately - remember, it is the material in contact with the workpiece that needs to be temperature controlled. 

You are going to need serious temperature control and far more heat removal than you think. This issue is what kills people with meth labs. Do the sums on energy involved and multiply by 10 for minimal safety. All that energy has to go somewhere and it is a lot better if it isn't going into you. Then think really hard about what energies are involved. Then do it again.

And again.

And again.

Then add another factor of 10 for what you haven't thought about.

Then rate your cooling and temperature control accordingly.

This costs.

A lot.

It really isn't worth it. I have worked with industrial quantities of dangerous substances and it is rather more involved than you think. Seriously, don't do it. Your skin costs more than you can afford. Facial scars are not attractive. And that's if you get it right.

Really, really, really don't try it unless it is remotely controlled and you can dispose of the waste reagents safely. And can afford the sort of temperature control solution that can handle high flow rates, small error and highly corrosive materials. It is no use having a bath at 0 degrees C if the workpiece is at 25 degrees C. Unless you agitate the solution violently, this will happen. Again remember Murphy.

Anodising is not hard and is safe enough - but temperature control takes it way out of the stuff you can do at home. And this is speaking as someone whose first degree was in chemistry more years ago than I care to mention.

For torch sized components you are talking about a volume of a litre or two - say a couple of pints. this does make things far easier. 90% sulphuric acid is not hard to get - check with your local lab suppliers - the cheapest grade will do just fine for this - analytical grade reagents can easily cost 500x that for industrial ones. Oleum (fuming (i.e. 110%) sulphuric acid) is dirt cheap as long as you do not attempt to buy anything nitrate at the same time (oleum + nitrates is how you make just aout all explosives). 

Given the War on Freedom (sorry, Terror), be prepared to have the FBI or your local equivalent asking very pointed questions when you buy the stuff. The chemical suppliers do speak to law enforcement - this is how a lot of meth makers get caught (in the UK anyway). I have had to sign all sorts of paper to buy acetone (nail varnish remover). Buying analytical grade stuff will usually stop this as it costs so much, nobody is going to use it to make bombs.

Now find a cooler that will keep the workpiece temperature controlled. The bulk temperature is mostly irrelevant, it is the temperate at the reaction site that matters. This means violent agitation (in highly destructive reagents) to keep the reaction site at the desired temperature. This is hard. Which is part of the reason why lab kit is so expensive. Not all the reason but a big part of it.

It can be done but is likely to cost a LOT and give unsatisfactory results. Chilling chemical reactions is not easy when you have to control the temperature in specific places. Mix in a lot of ammonium sulphate (This is how zero on the Fahrenheit scale was established) with your ice to get better cooling and it still won't be remotely adequate. See the posting above with pics about making knife sharpeners instead of torches.

BTW, what I know about current control could be written down then comfortably inserted in my eye so read up a lot on it first. And find out about HA3 processes. Anything that needs below 20 degrees C is likely to be rather hard to do. You will need to stir the acid rather strongly so that the temperature at the reaction site is conttrolled. and remember that the materials you are working with would far rather eat the stirring device.

If it needs more than a gallon of sulphuric acid leave it to the people who do it for a living.

At a minimum you are going to need detailed control over current (TIG welder?) and temperature (see above).

Good luck to you, but do be careful. Very careful.


----------



## greenLED (Jun 12, 2006)

:laughing: Yeah, working in a lab can be "fun" like that... :green: We've had our share of "fun" in our lab... usually because people are not paying attention or don't want to admit they don't know what they're doing. 


Dulridge, how does ~5mg of dry material sound for C & N determinations sound? :laughing: Your uncle would frown. I'm glad I'm not "cooking" acid digests any more.


----------



## dulridge (Jun 12, 2006)

I'm way out of date - last did any real chemistry 20yr ago. Probably can do with microgrammes what took me tens of grammes. 

Let's not go into "fun" with potassium hydroxide. Do not scale up reagent recipes without thought. I still have the scars to prove it. Especially when the other ingredient is silver azide (Think bullet primers but rather less stable)

Energy is the key - think about it all of the time and and then think of it again. And again.

Autoanlaysers take all the fun out of it though. Spectroscopy is very boring. At least when they are properly calibrated. I spent 3 months extracting samples into chloroform/cyanide (you can get very high on this mix, but it is best not to try) only to discover that the spectrophotometer gave readings dependent only upon how long it had been turned on rather than the cadmium content in the samples.

This was evidential work because an electroplater had been dumping very, very nasty stuff (pH 5 cyanide solutions loaded with zinc and cadmium) down a residential sewer - 3yr in prison if we could prove it in court. We couldn't.

But I digress again...


----------



## nima (Jun 12, 2006)

How much heat would it generate if run at very low wattage, and would this work?


----------



## dulridge (Jun 12, 2006)

How much heat?

I used to teach this.

In the best didactic manner, I leave this as an exercise for the student.


Or, in other words, not a clue.

It should be easy enough to look up the energy for 4AL + 3O2 -> Al2O3.

Remembering that this only effects the surface layer.

Local effects will confuse this. Remember that what I know about anodising at all is more than 30 years old. I work in SI (basiucally metric) units - these will need conversion if you use other units.

What is your ambient temperature?

What is the mass of reagent?

What is the mass of the workpiece?

What are the specific heats of the reagents (Assume the highest value of the mixture for all of it)?

How much energy are you putting in (joules/sec = watts)?

How many joules do you need to get rid of as a result? How many joules/sec do you need to remove. Add a zero at least.

Now rate your chiller and agitator device. Stirring is very important. Remember what it is stirring in - it must not get dissolved by the reagents. I'd suggest the output from the chiller gets drected at the workpiece.


----------



## HarryN (Jun 12, 2006)

I will not comment on the pros and cons of the setup, but as far as running at low current, this is not usually an option. The H2SO4 will dissolve the AlOx while you are growing it, so you need the rate of growth to be higher than the rate of dissolution.

I think the normal setup is to use Ti connections to the parts.

Surprisingly, many common organics will hold up to cold, concentrated H2SO4 used in HAIII growth than the hot H2SO4 of HAII.

The industrial guys have a lot of tricks and additives to keep poor quality H2SO4 producing decent results, but most people still wish they could obtain better, so it might be worthwhile for a home experimenter to use better quality stuff. I use semiconductor grade acids and cleaners whenever I need something, but that is a bit much for many people. Locally, it is pretty easy to obtain.

Pre cleaning the parts to near perfection cannot be over emphasized. A final rinse with drug store grade IPA is good if you can keep it away from the acid bath. (important)

Some people bubble air through acid baths during ano to keep even out / speed up the reaction. This also ensures that fumes will be very present of course. I would not be in a hurry to throw away acid too quickly, as it is a hobby and will not be used up that fast.

If I were neutralizing 1 - 3 gallons, I would probably use limestone / chalk / CaCO3 (outdoors) before diluting the mixture down the drain. That pretty much ensures it will be non toxic.


----------



## tvodrd (Jun 12, 2006)

Interestingly, a few years back, the best "professional" drain cleaners were concentrated H2SO4! A quart of it was pretty heavy. Specific gravity of it was way over that of water. I don't know if 0degc is typical of commercial baths, maybe colder? :shrug: IMO, the guy doing the dirty work estimates the total surface area of the parts and sets the current accordingly, or maybe the voltage determining the current is set as a function of the observed current. :shrug: 

Larry


----------



## markus_i (Jun 13, 2006)

Regarding those (partially angry?) responses to my post: from what I know about anodizing, you don't use concentrated or even 50% H2SO4, but roughly 50% diluted battery acid (at 37%, i.e. roughly 20% H2SO4 in the bath). The acid is only there because it's cheap, widely available, doesn't contain other metals (like CuSO4 would), provides mobile ions and is less dangerous/easier to handle than alternatives.
Yes, concentrated H2SO4 is nasty. Battery acid is at most a nuisance (at least as long as you're wearing eye protection and don't intend to wear the clothes you're working in outside the garage).

I'd just like to know what would have happened if we had been discussing PCB etching baths - my favourite is still HCl + H2O2 ;-). Seriously - I consider HCl (standard over-the-counter stuff) to be much nastier than (battery acid-strength) H2SO4. Adding H2O2 doesn't make it less dangerous - and the dissolved copper adds a nasty twist to the environment, you can't just dump it down the drain (at least not as private individual - if you are a mining company, things are apparently different). Just don't try this inside a room, wear a lab coat, eye protection and have the garden hose handy.

Nevertheless, good luck with your experiments, and keep us informed about the outcome (not entirely void of self-interest: we intend to build a home, and maybe I'll find some space for an anodizing setup there - and maybe a chance for experimenting with other electrolytes).

Bye
Markus


----------



## cy (Jun 13, 2006)

worked in a production plating shop for 3 years while attending school. 

I did setup a full sized anodizing tank once, but that's not normally done. once a vat is setup, you pretty much leave it alone. 

yes hard anodizing at home can be done, but due to amount of gear necessary. one must really be motivated to do so.

extensive cooling coils has to built-into tank. plus you would need the support rinse tanks and cleaning tanks. lower temp has to be maintained in hard anodizing or acid would attack buildup of anodic layer. VS std clear/color anodizing's much thinner anodic layer.

you would also need a massive DC power supply to deliver the 75 to 150+ amps needed to hard anodize. then you would need titium racks to hold parts etc, ets..

much better to send your hard anodizing needs to a proffessional plating shop...


----------



## TranquillityBase (Jun 13, 2006)

*nima*, it looks like they've beat you to a pulp, in light of your question for open forum discussion. 

I too was searching for information about HA, and had similar results, much info on type II, little to none for type III (home brew style) I did buy a kit for type II, as a starting point (haven't set it up yet) 

What I have learned over the past year, about HA or type III (through observation, in the shop that HA's my stuff, asking numerous questions, and internet searches) is this;

Lower temperatures, yes, the shop uses a chiller unit for the HA bath, and all the anodizing tanks have air agitation (temperature uniformity is important)

Higher voltage, yes.

Acid solution for the HA bath is not exactly the same, there are additive/s to keep the parts from burning (not sure what this is, but the net has the answer) You will find technical data on this subject. Don't give up.

My anodizer uses *aluminum racks for both type II and type III*. The racks are stripped of the coating, in an acid tank, after every run (type II and type III are dielectric)

I hope my tiny bit of info helps you, and please don't give up on your quest. If you see it through to the end, and need test pieces, I will send you various parts for testing/learning purposes, *FREE, I'll even pay for the shipping.*




*===============================================*
*Part masking*

*I use a brush on masking agent, that I purchased from Caswell plating, it's the same stuff my anodizer uses. There are other methods of masking off areas on a part, but the 'Mask-It' will cover most, if not all of your needs. *

*Good luck,*

*TB*


----------



## Tritium (Jun 13, 2006)

Must the acid be sulfuric or can another acid be substituted such as Citric Acid for the HA process? The reason I ask is I have extensive semiconductor fab experience so handling dangerous chemicals, amperage and voltages are "normal" to me and I have tubs and chillers obtained from the Fab surplus market (I knew I should have grabbed an old ventilated wet sink) as well as a large quantity of food grade anhydrous citric acid. I have been toying with the idea of setting up a shop to do work for the "Flashlight Community".

Thurmond


----------



## greenLED (Jun 13, 2006)

Markus, I'm sorry if my post came across as being angry. That was not my intention at all. There are very skilled and knowledgeable people on this forum, but there may also people who do not have the knowledge and/or expertise and decide to play with potentially dangerous chemicals without learning and following basic safety measures. My post was directed at the latter.


----------



## kromeke (Jun 13, 2006)

I've sent out parts to be hard coat anodized (type III) at work. The part I was anodizing was small, but the anodize shop had a minimum. If I recall it was $140 minimum order and all of our parts were under the minimum (in other words, I could have had more parts and it still would have been $140). I selected this particular shop because they would do mil-spec with dichromate seal. A lot of shops don't do the dichromate seal, because the EPA regulates dichromate. The only reason for the dichromate seal was because the customer specified it. We later got the spec changed on the part to a chemical conversion coating because type III anodize was way overkill for the part in question. 

I used AM Metal Finishing for my job. Keep in mind, this was a year ago and my part was very simple (stamped aluminum bracket, and nothing on it was masked off). There is also a Nickel acetate seal, and boiling water seal, in addition to the dichromate. Nickel acetate is more common. 

The parts I got anodized were very dark green in color(very dark, almost black). We did not have them dyed, I believe that the dichromate seal colors it dark green.

If you can get your part done for less than $200, that is very cheap in my opinion. The chemicals involved are nasty, and anodize shops do this every day. They know what they are doing. Look up MIL-A-8625 for more details on mil spec anodizing. It goes into more detail.


----------



## yellow (Jun 13, 2006)

I thought the main difference between "normal" and HA is:
more POWER (read: Amps)

where homemade anodizing might work with just a few Amps, HA would need some more (10+ at least?)


----------



## dulridge (Jun 13, 2006)

Tritium said:


> Must the acid be sulfuric or can another acid be substituted such as Citric Acid for the HA process? The reason I ask is I have extensive semiconductor fab experience so handling dangerous chemicals, amperage and voltages are "normal" to me and I have tubs and chillers obtained from the Fab surplus market (I knew I should have grabbed an old ventilated wet sink) as well as a large quantity of food grade anhydrous citric acid.



This is highly unlikely to work. the actual reaction is oxidation - aluminium going to aluminium oxide which happens naturally anyway. For this, you need a potent oxidising agent to thicken the extant oxide layer. Citric acid is not a potent oxidising agent as it is a weak acid, dissociating only mildly in water. What you are likely to do is electrolyse the water. Bubbles of hydrogen and oxygen are a bad thing to have on the workpiece. I'd try it though, just to see what happens. If it starts gassing - it isn't going to work.

The organic component might well introduce confusing factors.

Other strong acids might well work but aluminium chloride would be troublesome if you used hydrochloric acid.

Nitric acid would probably dissolve aluminium metal - almost all metal nitrates are very water soluble. I don't know if this is so though. Nitric acid is more expensive than sulphuric and the burns from it are rather nasty. Much nastier than the same concentration of sulphuric acid. Since it's almost impossible to make explosives without it, sales of nitric acid tend to be watched closely.

This may, or may not be a problem where you are.

Phosphoric acid might work but will cost a fair bit more than sulphuric.

Those are the common strong acids.


----------



## cy (Jun 13, 2006)

besides min costs of a run. hard anodizing has special masking and racking requirements. 

most cost effective way to hard anodize is with custom racks like larry custom built for his little lights. most folks don't realize extend masking/plugging plays in hard anodize proccess. 

this is why don's latest designs with separate ground path is so important. cost to anodize per part with special masking requirements could be $10 - $15 VS $1 - $4 per part if no masking/racking is required. 

a major factor against doing this at home is the ever present acid cloud. in time this cloud will corrode every piece of metal it reaches. imagine every piece of matal in your garage being attacked by acid.


----------



## David_Campen (Jun 13, 2006)

> discussing PCB etching baths - my favourite is still HCl + H2O2 ;-).


Heh, I used to sell unstabilized 50% H202 to a scientific glass shop where they were mixing it with hydrofluoric acid to etch tungsten.


----------



## cy (Jun 13, 2006)

for safety sakes generally I don't mention acid types and uses of. at a plating shop, one would be exposed to reagent grade acid/chemicals on a routine basis. 

think in terms of activating metals and strength of chemicals required.

due to hazardouse nature of chemicals used, epa regulations plays a large part of costs.


----------



## Sawtooth (Jun 18, 2006)

Here is an interesting site I found awhile back. I know it is not HA (i.e. type III) -- it is
type II, but it gives some info on both. And there are starter kits for type II anodizing...


----------



## Sawtooth (Jun 18, 2006)

Oops. Here is URL:

http://www.focuser.com/atm/anodize/anodize.html


----------

