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"Current/Voltage for Aluminum Anodizing"

Current question:

June 19, 2021 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread Aijazullah

Q. Planning of having a anodizing process along with existing powder coating plant.
our requirements will the tank size 6000L x 1000 Wide x 1500 Depth , what capacity rectifier should we look for. i appreciate if you could respond to this.

Nazeer Mohammed
- Manama, Bahrain
^


June 19, 2021

A. The rectifier and chiller are not sized to the tank, you size the rectifier to the surface area you put in the tank. Come back, tell us the surface area and thickness you desire, the kind of anodizing (II or III), and we will advise your requirements.

robert probert



Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina
probertbanner
^




Closely related Q&A's, oldest first:

2001

Q. Hello Folks,

I have been anodizing small parts to build production machines for the company where I work. I started the anodizing process by my own from reading. I have been using successfully a 35 amps/ 12 vdc rectifier. If I want to expand this process to a larger capacity, what would be the rectifier range to get in order to assure enough current/voltage for any area to anodize? I will appreciate also any suggestion of how to get used anodizing chillers.

Thanks,

Reynaldo Arroyo
- Valencia, California
^


2001

A. Reynaldo,

I'm assuming you are doing decorative anodizing, as it doesn't sound like your current power supply is enough for hardcoat. You should be anodizing at 12-15 amps per sq ft of surface area for decorative anodizing, so size your rectifier accordingly (20 volts should be more than sufficient). If you want to increase your load size, you'll also want to make sure your cooling system can handle your needs, as well. If, indeed you want to hardcoat your parts.. you'll need to size your rectifier for 25-40 amps/sq ft (you'll probably need 50 volts, or more). Check Metal Finishing magazine, or PF magazine, there are a lot of used equipment ads in there.

Marc Green
Marc Green
anodizer - Boise, Idaho
^


"Surface Treatment & Finishing of Aluminium and Its Alloys"
Wernick, Pinner & Sheasby
from Abe Books
or

affil. link

2001

A. The required voltage is largely dependent on the distance from the anode to the cathodes. If the spacing you presently use will be adequate for the larger parts, then 12 volts will remain adequate, although it sound low to me and I'd feel more comfortable with an 18-volt rectifier.

The amperage required is proportional to the surface area of the load. If it will be 50 times larger, the amperage should be 50 times higher. As a guideline if you don't have enough data to do the proportioning, figure that you will probably not anodize at more than 20 amps per square foot.

Suppliers of used rectifiers can be found in finishing.com's Equipment Directory.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^


2001

A. Dear Reynaldo

Sizing a rectifier is easy, if you are going into serious production and want to have up to date equipment. For type II you will need 20 to 30 amps per sq ft. at 18-24 volts. For type III it will be 30-40 amps sq ft at 75 volts. Automatic ramp and timer are also essential. Cooling and agitation are extremely important to maintain quality production work. I also highly recommend using aluminum cathodes to save energy and eliminate a lead source

drew nosti
Drew Nosti, CEF
Anodize USA
supporting advertiser
Ladson, South Carolina
anodizeusa1
^


2001

? Drew...20-30 ASF for decorative anodizing? hmmmm..sounds a little high to me.

Marc Green
Marc Green
anodizer - Boise, Idaho
^



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



Which DC Power Supply is right for me?

2004

Q. All right folks, excuse me if this sounds quite elementary, however, I am unable to determine the answer to the questions which are to follow.

First, here is some background information on my shop setup so far. My tank's internal dimensions are as follows : 36" length x 12" width x 18" depth which calculates to approximately 33.7 US liquid gallons per tank.

This tidbit of information brings me to my first question. As a general rule of thumb, is there a maximum amount of aluminum surface area which may be processed in a given tank size? I guess to simplify my question, is there a standard "aluminum surface area to amount of electrolyte" ratio an individual should consider when anodizing or is the sky the limit? Can I cram as many parts as possible in the tank and as long as I maintain an anode:cathode surface are ratio of approximately 3:1? (I realize that tank overflow is a potential hazard. I am searching for a hypothetical answer here).

Secondly, I am currently in the market for an anodizing rectifier (DC power supply) and really want to make sure that I purchase the correct thing the first time around. Since I find it difficult to believe some sales representatives and feel that they are more often than not, looking out for their own best interests (excuse me if you are in sales, I realize that not all sales reps are the same and I was simply generalizing from my past experiences). I can't afford to make a mistake in this department. As I know nothing about DC power supplies, perhaps somebody can bring me up to speed - a crash course perhaps. In several places I have read that minimal ripple is best suited for anodizing. Often I read that 5% ripple is just right. Can somebody explain to me what "ripple" is and what affect is has in the anodizing process?

I feel that a rectifier with an output range of 0-24 volts and 0-400 amps will be adequate for my needs given my tank dimensions. What is the highest voltage output that one would recommend for type II anodizing? Would anyone here care to advise me on my rectifier output size, knowing my tank dimensions? Keep in mind that this power source is not going to be utilized in your average, everyday garage setup. I will have adequate power to run this unit.

The next question which stumps me is ramp control. I am not exactly clear on which ramps up during the process of anodizing. Is it the volts or the amperage? I currently believe that the voltage does the ramping, however, I just read somewhere that the amperage ramps up. Perhaps it was a typing error - I just want to clarify this. The VOLTAGE ramps up - correct?

Having said that, how does one calculate the ramp up speed?

Last question and this may be really dumb, bear with me. I have looked at many different used DC power supplies on the internet. It seems to me that most of these units are simply big boxes without any means of control (no dials, gauges or knobs - just electrical hookups). Would an industrial sized rectifier normally come with a control of some sort or is this commonly a separate purchase? If indeed that two are sold separately, which makes up the bulk of the overall cost, the power supply or the controller?

Thanks to all who have aided me in the past and to those who will direct me today. Without you people my journey to understand the previously understandable would have been far too great a task! Cheers all!

daniel degueldre
Daniel DeGueldre
   anodizing shop entrepreneur
Ste. Anne, Manitoba, Canada
^


2004

A. Whew! That's a lot of questions. I'll try a few of them

-You can pretty much crowd as much work into your tank as you want. Shielding isn't much of a problem in anodizing, but stay a few inches away from the cathodes.

The maximum voltage you will need for type II will probably never be more than about 19 volts.=, maybe less.

400 amps is plenty for your size tank.

You can ramp up manually over a period of about 5 minutes. Most T-II won't require any ramp up at all.

Ripple isn't a major concern in anodizing. 5% or 10% should work okay. yes you need voltage/amperage control. I suggest you buy from a reputable manufacturer of plating rectifiers. they will help you select what is correct.

The biggest problem you're likely to have is cooling. Budget at least as much for a chiller as you do for the rectifier.

jeffrey holmes
Jeffrey Holmes, CEF
Spartanburg, South Carolina
^


2004

A. Hi Daniel,

I've been reading the questions that you've been posting for a while now and it sounds like your shop is almost ready to go. It seems like you want to make sure that your setting things up correctly and that you are willing to do a little research to make sure that you don't make any errors that are easier to avoid in the beginning - that is a very good thing.

That being the case, and I'm sure that someone (probably Ted) has said in the past in response to one of your letters, trying to learn EVERYTHING from posting questions on the Internet CAN work - but it is a lot more efficient to crack a book for a lot of the information. Get a copy of "The Surface Treatment and Finishing of Aluminum and Its Alloys" by Wernick, Pinner and Sheasby and you will agree that it was the best investment that you could make. It will more than pay for itself (and the time it takes to read it all the way through - it's about 1000 pages) just in preventing mistakes.

It has, for example, detailed sections describing the effects that voltage, amperage, ramping times and the manner in which the power is turned off after anodizing is done have on the finish. If you already have a copy, check out pages (fifth edition page numbers) 380, 387, 398, 421, and 969-971. I checked my notes and those pages should have some really relevant information to some of your questions.

Good luck!

Jim Gorsich
Accurate Anodizing Inc.
supporting advertiser
Compton, California, USA

accurate anodizing banner
^


2004

thumbs up signThank you so much for that Jim. I have already indeed looked into purchasing this pair of text books. It is without a doubt an investment as much as it is an aid I'm sure. Unfortunately, as dollars are spread thinner and thinner every day while purchasing equipment and supplies, these books are forever pushed to the back burner. To date this entire operation has been built on our own dollar, no bank loans or grants have been issued here. This of course calls for strict budgeting as I am sure you can imagine.

You were correct in assuming that my shop was nearing completion. It may be for this reason that I procrastinate on purchasing these texts. I realize this may in fact be my downfall as I to believe that no single resource should ever be one's sole center for knowledge. For this reason I have been dabbling within our local libraries and speaking with others in the field. I must admit, however, I do find www.finishing.com to be a tremendous help and even perhaps a crutch. Should I find myself misunderstanding something I read or confusing something I hear, I can always come here and have myself straightened out. For that I am very appreciative - you have no idea the progress that I have made here in the past few months. Though I realize I have many more struggles ahead I am willing and able to overcome them - particularly if Ted and people like you are behind me! Cheers all!

daniel degueldre
Daniel DeGueldre
   anodizing shop entrepreneur
Ste. Anne, Manitoba, Canada
^


2004

A. Hi Daniel,

I can definitely understand not wanting to drop the full price on the book - the $500 typically asked for it is pretty steep. However, every once in a while you can find it on sale and it becomes a lot more affordable (not to long ago I picked up a copy of the 5th edition through the ASM website for $200).

That being said, if my notes are correct you may want to look at questions 51573 and 12130 - the first deals with sizing a chiller and the second deals with sizing a rectifier.

Also, if you haven't yet, you may want to check out the "100 Q and A" at the Anodizer's Plaza reached through the "WWW links of interest" link on the home page. It has some very informative and interesting information that helped me a lot before I bought my copy of "The Surface Treatment and Finishing of Aluminum and its Alloys".

Good luck,

Jim Gorsich
Accurate Anodizing Inc.
supporting advertiser
Compton, California, USA

accurate anodizing banner
^

----
Ed. note Nov. 2013: Unfortunately, "Anodizer's Plaza" is long gone.



April 14, 2009

Q. Mr Daniel DeGueldre I have been experimenting with anodizing, and just like you I want to open an anodizing business in Malta. What do you plan on anodizing when you'll open your shop? Do you think it is worth the money invested? and is there enough work to keep you going?
Every one can feel free to reply.
Thanks in Advance.

Alan Vassallo
- Malta
^


2004

Q. Regarding anodizing rectifiers big and small, can somebody set me straight on what exactly constant volt/amp control is? Secondly, what makes it so important?

Thanks so much everyone and please excuse my ignorance.

daniel degueldre
Daniel DeGueldre
   anodizing shop entrepreneur
Ste. Anne, Manitoba, Canada
^



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



" Rectifier needs for large scale type II anodizing "



September 25, 2012

Q. A few associates of mine and myself are researching the possibility of getting into large scale industrial anodizing. I myself am a novice in the anodizing world so I apologize for my lack of knowledge.

My question, from what I can tell from a little research does not have a straight forward answer. So if someone would help me in the right direction I would very much appreciate it. We plan to have some sizeable tanks manufactured for our purposes. about 240"L x 48"W x 72"D with the intentions of packing anywhere between 10 to 20 18 ft by 6 in pieces at a time to be anodized. My question to all you knowledgeable anodizers out there what size rectifier would be needed for a process like that? Any information would be helpful.

Also, I know cooling is going to be most my battle, but rectifier size is where I am at a loss. I'm just looking for some idea before I call a rep from a major company.

Josh Price
- Atlanta, Georgia, USA
^


September 25, 2012

A. Hi Josh. It will probably be closer to 10 pieces than 20 if you figure two 54" high rows, with gaps between the 6" high pieces.

You should probably figure 18 volts and 18 amps per square foot for the rectifier sizing.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^


September 26, 2012

Ted,

Thank you for your response. You are absolutely right, I should have figured 10 pieces. Figuring for 18 amps per square foot helps a lot, thank you again.

Q. I have a related question, and once again excuse my lack of knowledge. The pieces I have in mind look like this ] pretty much bracket shaped with the top and bottom "legs" being 2" and the longer part being 6" roughly by 20 feet long. When dipping say 10 of these I know you should hang them either like [ or with the opening opened up to prevent bubbles forming as they would if the piece opened down. (hopefully that's not confusing).

My question is if dipped with opening up will the inner sides of the piece be less anodized than the outer sides? Or is that insignificant because the piece is positively charged so the reaction is attracted all over the piece?

Also if the insides of the piece will be equally coated is it possible to keep uniform quality dipping two parallel racks simultaneously?

That is a lot of questions, any response would be helpful.

Thank you

Josh Price
- Atlanta, Georgia, USA
^


September 2012

A. Hi Josh.

I would rack them like this --

]    
   [
]    
   [
]    
   [

Anodizing is an insulating coating which therefore tends to be rather uniform.

But people with no anodizing experience trying to design an anodizing installation would be a serious mistake. You should retain an anodizing consultant, and the sooner the better because the most important decisions are made early on. I did plating and anodizing line installation consulting for over 30 years and in many cases I felt more like a damage-control specialist than a designer because people had traveled a path of no return for too long before seeking help :-)

Good luck,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^


September 28, 2012

Q. Ted

Thank you again for your quick response, and great advise. Since we are walking in unknown territory we are definitely planning on contacting a consultant in the very near future. The questions I have posted are for a vague understanding, and I really appreciate your help.

I was also wondering with, with all of your consulting experience do you have any suggestions on who or what firm you would lean toward if you we're to contact a consultant?

Thank you

Josh Price
- Atlanta, Georgia, USA
^


September 28, 2012

A. Hi Josh. Advertiser support is what makes this site possible, and we have at least two world-class anodizing consultants listed in our Consultants Directory.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^



October 23, 2013

Q. My question is for hard anodizing, what is the mechanism of supplying the amperes, like we have to supply at one time or by gradually? Like 2 amp to 5 amps for 5 min then increase? So kindly provide the amps supply mechanism. And for hard anodizing why we choose the amps mechanism instead of voltage?

Aijazullah Tajir Attari
- Abu Dhabi, UAE
^


probert book
Aluminum How-To

"The Chromating - Anodizing - Hardcoating Handbook"
by Robert Probert
(How good is it? Finishing.com has sold over 700 copies without a single return request)

October 25, 2013

A. Hi, Aijazullah. Ramp control for anodizing can be as complex as you want to make it. I've been to shops which use very complicated digitally controlled voltage/amperage profiles in their belief that it makes for hard anodizing that is better in some fashion, and that may be.

But the basics are simple: Ohm's Law tells us that I=E/R, that is, Current equals Voltage divided by Resistance. The hard anodizing film is a very good electrical insulator; that is, it creates a very high Resistance. If Resistance is very high, we need a very high Voltage to drive Current to continue to build the anodize film. However, when you start anodizing, Resistance is very low, so if you apply a high Voltage, then a very high Current will result and the parts will fry/burn. So you must slowly ramp up the voltage, in proportion to the thickness of the anodizing to maintain a reasonable current throughout the cycle. Or, more simply, just control the process with constant current.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^


November 11, 2013

Q. Hi friends,
Yes I understand that for hard anodizing we have to apply the amps gradually; I want to know what is the meaning of gradually? Considering an example like I have to supply say 20 Amps for a set-up, then how should I start it with how many amps in the beginning and then at what interval shall I need to increase the amps?

Aijazullah Tajir
- Abu Dhabi, UAE
^


November 13, 2013

A. Hi Aijazullah. As I said previously, the answer can be as complex as you want to make it. If you want to make it complex, the answers depend on the alloy being processed, what temperature you can truly hold at the work surface, which additives (if any) you are using, and several other factors which take many pages of graphs and tables to present. Jim Gorsich described on what pages in the industry's most important reference book to find all those charts and tables and research answers to your particular situation. On top of that, some specialists have implemented additional proprietary current-time profiles they use which they feel are superior, and which they can't be expected to share.

But on the other hand, I think you may not be taking the time to carefully read and truly understand the very simple and important concept that has been explained, i.e., that in lieu of complex current-time profiles you can simply anodize at constant current. Hold your 20 Amps per square foot from start to finish and see how your hard anodizing works; then try again at 30 Amps per square foot. Good luck.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^



October 24, 2020

Q. Hi, I have been anodizing using a fairly robust, but small scale setup. I typically do not ever do parts larger than about 100 square inches. I have just set up a new system and a new constant current power supply with 10A, 30v capabilities. I'm using around 12% acid concentration derived from battery acid at 3:1 distilled water to acid. My question or problem is that I do not seem to be getting enough volts for the amount of amps I want to use, and my volts seem very low if compared to 720 rule. I have reduced acid concentration slightly, removed cathodes, and still find the volts seem low.

I would love lots of input regarding the volts/amps relationship. I do understand electricity, and current, and how its derived: volts x amps = watts, etc. But I am having trouble understanding the variables here, if the watts are a factor, how the voltage affects the outcome of the anodic layer properties, etc.

I have a part running now, are these parameters OK? 44 square inch, 6061 T6, 5 amps and 18v. I think the volts should be higher.

Thanks very much, and I have enjoyed the good info here!

Jason Brown
- Laguna Hills, California
^



We'd like to give credit for this graphic explaining Ohm's Law (A = V / Ω) but see it on many websites without info of whose work it actually was :-( ohms law
October 2020

A. Hi Jason. Electricity can be hard to understand and visualize because it is invisible and rather abstract.

Amperes is the flowrate of the electricity, actually the number of electrons traveling past a point in a given time period, analogous to the flowrate of water; Niagara Falls would be analogous to very high amperage, the amount of Pepsi flowing through a plastic straw would be analogous to very low amperage.
Voltage is analogous to water pressure; it takes strong pipes and high pressure pumps to provide water to sinks & toilets near the top of skyscrapers, even if only a slow drip of water is wanted, whereas a duct tape patch can hold on an above ground pool even if it holds thousands of gallons.

Although you may understand some aspects of electricity very well, I think you have your understanding of Volts and Amps interchanged based on your question. Voltage does not come into play in the 720-Rule, which is simply Faraday's Law of Electrolysis with a couple of constants related to aluminum factored in. I'd suggest that you review our introduction to Faraday's Law as a starting point for a deeper understanding of it. Your operational parameters sound fairly right. 5A for 44 sq in. equals 16.36 ASF, and that's the number for your 720-Rule calculation. The 18V seems somewhat higher than you ought to need for 5A but maybe not outrageous especially if your meters aren't precise ... but you can't independently control it (voltage and amperage are tied together by resistance).

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Aloha -- an idea worth spreading
finishing.com - Pine Beach, New Jersey
^

Remaining questions on rectifier sizing for anodizing? Please see also --

Topic 14061 "Anodising rectifier and power requirements"

Topic 0967 "Increasing Type III (Hardcoat) Anodizing Capacity"

Topic 23398 "Rectifier size (current, voltage) for Chromic Acid Anodizing"



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