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Hardcoat vs. regular anodize

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I need to know the difference between Regular anodizing vs. Hardcoat anodizing. Are the chemicals interchangeable? Etc.?

Thank you.

Gary W. Schooley


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In anodizing, the electricity converts aluminum metal to non-conductive aluminum oxide, while simultaneously the acid is dissolving the coating. The process is thus self-limiting because the oxide impedes current flow and when it reaches a certain thickness the current flow cannot build a coating any faster than the acid dissolves it.

So, in simplest terms, hard anodizing involves a higher voltage rectifier and lower temperatures of about 0 degrees C. This allows more current to flow, for a heavier build, while reducing the acid attack on the coating.

They both employ sulfuric acid of about 10 to 12 percent concentration.

There are proprietary extra ingredients that can be added and which purportedly build a better coating or allow the hard coat process to operate at higher temperatures.

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


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I have 30 years of experience in anodizing and I have found 16-18% Sulfuric concentration works best.

Raymond Hendrix
H&H Equipment

Troy, Tennessee



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Thanks, Mr. Hendrix, I'm sure you're correct. My 10-12 percent, while perhaps approximately correct by volume, was not really the correct answer, and I appreciate your catching the error. Some published values in the reference books include, by weight, 15 percent and 185 g/l.

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

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You mentioned additives that allow hard coat to be run at higher temperatures. What are they, where do you get them, and how high a temperature will they let you run at? Is any other special equipment needed?

Terry Burgess
Consolidated Metal Technologies


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Terry,

There are several companies that offer an additive. Check out the list in the Metal Finishing Guidebook or similar reference. It does take a higher voltage and it does not produce a true hardcoat, but one with some of the properties such as a little less hardness, a little less wear. In some cases this will suffice for real hardcoat. Companies like Metalast that have a excellent additive will not sell it alone and it takes special equipment to operate it and it is a licensed product.

Most allow you to "hardcoat" in the 45F range vs 32F. Some are higher.

James Watts
- Navarre, Florida


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Dear Sirs :

We are about to initiate an important aluminum operation in Peru (South America) and the only missing piece in our project is the anodizing plant. We haven't being able to contact directly manufacturers of these plants or second hand sellers and we would highly appreciate if you could recommend us where to turn for this information.

As extra information, we would be processing 300 tons a month.
Thank you in advance for your help.

Manuel Tirado C.
- Peru


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Dear Manuel Tirado C.

In our Equipment Directory at www.finishing.com/equipment you will see a good number of suppliers listed. You may also wish to consider having the system designed for you so that you can have portions of it supplied or fabricated locally. In that case, I can design the plant for you.

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

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Dear Manuel Tirado C.

H&H Equipment is a supplier of new and used anodize equipment.

I have 30 years of experience in anodizing. We can supply you with equipment and arrange for installation.

If I can be of further assistance, email me.

Raymond Hendrix
H&H Equipment

Troy, Tennessee

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