Some newbie questions...

[kiwijetpilot]

Hello from one of the far-flung reaches of the known world! It's a nice day here in New Zealand.

I would very much like to try LCD anodising, but as I live outside the USA and it appears that Caswell do not ship most of the components internationally, I am probably out of luck.

So - two questions.

First, does anyone know what is actually in the LCD chemicals, or is that a trade secret? Maybe I could make up my own.

My little line consists of 15 gallon "fishboxes" which are very thick polyethylene. I want to be able to do bigger pieces. My plan so far, given that I can't obtain the LCD stuff, is to use a degreaser, followed by a rinse and then an etch/desmut product available here called Metalbrite. Then a rinse and the anodise bath, followed by another rinse, dye, hot seal.

My second question is power supplies. There seems to be at least two schools of thought on this, with you guys being constant current devotees, and other sites saying constant voltage is better ("what the professionals use"). Is there any hard evidence either way? And for my 15 gallon tanks, any idea how big a supply I will need?

I'm intending to use my line for doing a lot of custom car parts, so no doubt I will have to learn more about cast and welded items, but the two questions above will do for now!

Thanks for any info you can give me.

[sswee]

The chemicals are not that difficult. Which ones do you need to know about? Caswell's products are great, but if you cannot get them, there are work arounds. The dyes are the only one I recommend not trying to get around. This comes from first hand knowledge.

On PS, again from first hand, CC is the way to go. I started out with CV. It can be done without a doubt but needed more attention during a run. Another benifit to CC for me was more consistant results. After switching to CC, the only problems I had were related to cast material. Alot of automotive parts use very poor material for castings. As for size, it will depend on what the largest part you intend to run. You will need to caculate the surface area.

[Fibergeek]

Welcome Kiwijetpilot.

Regarding power supplies:
It would be more accurate to say that there are two (and only two) camps on this issue; those who understand electricity and those that don't. The fact that CC has a provable mathematical basis (Faraday's Law and Ohm's Law) and CV doesn't makes this a non-issue.

[kiwijetpilot]

Thanks for the help guys.

Regarding chemicals, all the ones that can't be shipped, so that would be the anodise and chrome stripper (PROD ANSTP1G), Aluminum De-Oxidizer & De-Smut (PROD ALDEOX2, and Anodizing Sealant LT (PROD ALSELT1.

My main problem is that I don't know how critical the chemistry is to success. I would have thought that a variety of commercially available alternatives in NZ would do the job, but without knowing exactly what the stuff is, it is hard to know what to get.

For example, the makers of the Metalbrite product I mentioned insist that it will clean, de-ox and desmut... but does it do it well enough? I guess I'll just have to experiment. Expensive mistake if it doesn't work, though.

Regarding power supplies, is it true then that big plants work with constant voltage, or do they in fact use constant current? I'm still trying to get my head around this one.

[Fibergeek]

I will address electrical issues, and leave the chemical issues in the capable hands of Sswee. All are encouraged to join in of course.

Do a search in this forum (button at the top of the page) for CC. You will find many threads that will help explain this.

The only way an anodic coating can be formed using "voltage anodizing" is by mimicing CC by manual adjustment of the voltage to control the current. "Voltage anodizing" is an oxymoron since it attemps to violate Faraday's Law. This has nothing to do with the scale of the operation, the physics is the same.

[sswee]

As for the chemicals, the anodise and chrome stripper is Potassium Fluoride, the DeOx/DeSmut is a mix of sulfuric and phosphoric acid, the Sealant LT I am not familiar with because I use the regular sealer which is nickel acetate.
At this time I do not use the stripper because I physically strip the parts by blasting, sanding and polishing or a combination depending on the look I want for the part.
The DeOx/DeSmut can be substituted with common lye (sodium hydroxide). It can be usually found in most drain cleaners here. Start at about a 10% solution. The problem with this solution is it is not as predictable on the results as the Caswell product. You need to test times and concentrations for best results. It will also take the shine out of a polished part if left in too long.
I am not familiar with Metalbrite. Do you know the ingredients?
As for sealing, I have had good luck with boiling to seal. I haven't been able to see a visual difference between the parts that were boiled to seal and the ones that I used sealer on.
One thing you haven't said anything about that is important. The water to mix any of your tanks and for rinsing between tanks needs to be RO or distilled. Rain water can be used.
If you can swing it, the Caswell plating manual has a load of information in it. You can get a hardcopy or online version. Between it and the guys on the forum, it didn't take long for me to get good results.
If I missed anything or wasn't clear, just let me know. Best of luck. SS

[kiwijetpilot]

OK, it turns out the Metalbrite is mainly phosphoric acid, with some hydrogen flouride and a surfactant thrown in. I guess I need to know if that will strip previously anodized items.

I plan on farming out the cleaning side to a local bead-blaster, so I won't be using a dedicated chemical stripper either. I might end up using a product called Carbon Off, which is Phenol and Methylene Chloride, with some detergent, corrosion inhibitor and water thrown in.

I'll invest in a manual, the more you read, the better!

Thanks for all the info,

Simon

[M_D]

Traditionally anodizing has been done by controlling the voltage, but now many commercial anodizers use CC instead. If you go with a CC power supply you will be ahead and won't regret it.

As far as chemicals go, the most essential one is sulfuric acid for the electrolyte. Then you need something to clean the part so water will sheet, scrubbing with dish soap and warm water until the water sheets over the entire surface will do the job in many cases, although it is time consuming and tedious work. It is much easier to immerse the part(s) in a solution and let it do the work though, and on complex parts with difficult places to physically reach, it is the only way.

A stripper or etch solution (such as sodium hydroxide/lye) can be used to deoxidize parts, as can bead blasting, sanding, machining, or other method that leaves a new surface. The de-oxidizer/desmut solution, in my opinion, isn’t enough to thoroughly deoxidize some parts in a timely manner, but it does an excellent job of removing the smut left after etching or stripping. That smut is a layer of various metals found in the alloy, that is left behind after some of the surface is “eaten” away by the chemical(s) used to strip, etch, and deoxidize. As sswee said, there are work arounds that can be used. Having certain chemicals can save a lot of labor though.

[kiwijetpilot]

Thanks.

I spoke to a guy today who has been in the anodising industry for 30 years. He said that he used to use a vibratory tumbler to desmut, or just warm soapy water after the etch. he would then rinse and re-etch for a couple of minutes.

He also mentioned the need to vigorously agitate the anodising bath with compressed air - he said that it helped cool the solution, as well as preventing localised defects. Makes sense to me.

So, to summarise - it doesn't really matter how you clean/etch/desmut, as long as you present a clean piece of aluminium, with no oxidation, grease or smut, to the anodising bath?

The guy mentioned above also said that automotive alloys (which I will mainly be working with) tend to have a very high silicone content, and are very difficult to desmut properly. Anyone had any experience with these alloys?

There is a company over here working on a new chemical desmut for these alloys, but it isn't ready yet.

Thanks for all the help!

[sswee]

Sounds like you are headed down the right path. I am still trying different things on cast automotive parts to see what works best and consistantly. The cast parts I've done so far were polished to mirror shine, degreased, etched, DeOx/DeSmut. And after anodized and dyed some had discolored areas under the anodize. The dye color was even and deep over the entire part. It appeared like the material was trashy and not mixed to an even consistancy. I'll let you know if I find something that works on a regular basis. SS