Authoritative Answers, Fun, & Aloha -- no cost, no passwords, no popups
(as an eBay Partner & Amazon Affiliate we earn from qualifying purchases)

Home /
Site 🔍
pub     mobile?
Metal finishing Q&As since 1989


Calculating cooling needed for aluminum anodizing

(to provide context, hopefully helping readers more quickly understand the Q&A's)

Our "Intro to Anodizing" quickly explains the different types of anodizing including Type 1, 2, and 3.

Q. We are in the process of building a new line for anodizing, and we would like to know if we can calculate the amount of heat that is generated in the anodizing tank, so that we can get the right size cooling system.
So if we anodizing at 24 Volt x 300 Amp = 7200 Watts. How many of the Watts are used for heat generation?
On our current line the cooling system is way too large.

Poul Slot Mikkelsen
- Vildbjerg Denmark
December 2, 2021

A. Hi Poul. If this is Type II anodizing, operating at about room temperature, then essentially 100% of the Wattage added must be removed. However, "duty cycle" is also a factor. The tank is empty some portion of each hour, plus you start the anodizing process at lower voltage and current. Further, when people say they anodize at a given current, they are usually talking about their maximum amperage; sometimes the racks aren't full or they're anodizing smaller parts.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey
December 2021

Disambiguation: Please see also --

Topic 51573, "Hard anodizing chiller sizing"

Topic 58129, "Cooling of home/D-I-Y anodising baths"

Closely related Q&A's, oldest first:

RFQ: I'm looking for a place to get a cooling system for my anodizing solution when I anodize large load the tank starts to get really hot; the cooler has to be able to handle 55 gals of liquid and keep it at 70 degrees + or - 2 deg

Thank You

Larry Frey
machining - blueball , Pennsylvania

Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)


A. With some exceptions, chillers are sized by the load. A quick way that is fairly close, is to consider that the entire amperage of your biggest load is all going to heat.

Volts times amps = Watts

Watts times 3.412 = BTU's

BTU's divided by 12,000 equals tons of chilling capacity

A 55 gal tank will take somewhere between a half ton and a ton, depending on your load and power supply.

The heat exchanger is a more difficult calculation for size.

Best to have a professional do that one for you.

James Watts
- Navarre, Florida

A. Dear Larry,

Without being rude, why is your tank so small? One reason you're heating up so quickly is because the ratio of work to solution is too great.

You could try running your rinse water thru a coil in your anodising tank before it enters the rinse, otherwise you are going to have to "make something" out of a refrigerator.

I would suggest that you look to a larger tank, nothing less than 200 gallons.


John Tenison-Woods
John Tenison - Woods
- Victoria Australia

A. We used lead pipe (that we made) in bath for cooling. I don't know the calculations but we obtained better results than with any other stuff.

mustafa demirci
chrome plating - turkey/istanbul

A. Hi. All of the responses sound good! But I agree mostly with John that the tank should be bigger. Then it may be that if it is loaded infrequently, just cooling with a lead pipe and the city water that feeds the rest of the line may be enough. There could be a 3-way valve that sends the water through the tank when the tank exceeds 70 degrees, and bypasses it when the temperature is lower than 70 degrees.

But don't forget a backflow preventer if connecting to city water. Good luck.


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

Multiple threads merged: please forgive chronology errors :-)

Which type of Mil A-8625 anodize coating requires refrigeration coils?

I need to know which type of MIL-A-8625 / MIL-PRF-8625 [on DLA] anodize coating requires the use of refrigeration coils, is it Type I, Type II, or Type III? Thanks for your help.

Marilyn Pitts
- Hindsville, Arkansas

Hello Marilyn. Type I operates at over 100 °F so cooling might not be required. Type II probably requires cooling since the operating temperature is about 68 to 70 °F., so no heat is lost to the environment whereas substantial heat input can be generated by the anodizing current. Type III operates at 28 to 32 deg. F., so it always requires refrigeration.

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

Q. Can someone tell me how to calculate the cooling load for an anodizing bath?

Gap Dewalagama
- Sunshine, Victoria, Australia

A. That one's easy, Gap. The rectifier voltage x the rectifier amperage = watts of heat input that must be removed. But that would be for a 100% duty cycle (assumes the tank is never empty, never ramping up, and always operating at full voltage and amperage.

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

A. ...Andmultiplydivide Watt-Hours by 3.414 to get BTUs.

Tom Gallant
- Long Beach, California, USA

A. And add to that the heat carried in by parts plus the heat transferred in through tank walls and surface and agitation air, which can be considerable in hot weather.

jeffrey holmes
Jeffrey Holmes, CEF
Spartanburg, South Carolina

A. Jeffrey is right for Type III, of course, and sometimes secondary sources of heat input and outflow can be significant. But no calculation ever takes everything into account (it's always a rounded-off estimate), and if this is 68 - 70 °F (room temperature) anodizing rather than hardcoat anodizing, those factors become much less significant. The anodizing tank is never full 100% of the time, and I personally never encountered a problem designing cooling systems for room temperature process tanks based just on the anodizing or plating rectifier wattage input.


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

none is made possible by ...
this text gets replaced with bannerText
spacer gets replaced with bannerImages

(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

Chemicals &
& Software

About/Contact  -  Privacy Policy  -  ©1995-2024, Pine Beach, New Jersey, USA  -  about "affil links"