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topic 4723

Chromic acid flakes same as crystals? Copper heater okay?


I am a graduate student working on hard chrome plating as part of my thesis. I have designed a big chrome plating bath - 50 gallons. I have a 2 kW copper sheath reboiler heater lying around in my lab. I was wondering can I use it for heating the chromium bath. I know that chromic acid etches copper but how bad is it? The reboiler heater takes about 4 hrs to bring the temperature to the desired level. Will it ruin the heater if I keep use it for 4 hrs and take it out?

One more thing - can I use chromic acid flakes instead of crystals for preparing the solution? Are they equivalent?

Thank you,


Susheel Yadav
University of Cincinnati - Cincinnati OH USA


A big chrome tank is like the one Kelly AFB had. You could probably put 2 VW bugs in it and have room to spare.

A copper heater will last about 3 hours plus or minus 2 hours.

The form of chromic acid makes no difference. One dissolves a little faster.

Have you talked to your advisor on how you are going to legally dispose of this material after you are through with it? Get your checkbook out, it is expensive!

Has this been passed by the school lawyer. I would expect a very very dim view of it.

What do you have for a hood and an exhaust system. EPA air quality has to approve it before using it and the cost of doing the stack analysis used to be $4,500.00

If it were me, I would try to arrange to buy some tank time from a local chrome plater, Hard chrome is not exactly the same process as decorative, so you will need to find the correct shop. There should be several of each in your area.

James Watts
- Navarre, Florida


Your general attitude about this one is undoubtedly correct, Jim. But . . .

I'm not sure that it is actually illegal to just pull the plug and dump this toxic stuff down the drain as long as he's at the university. I recently did a project for a development lab at a university that was making prototype parts for the military and was shocked to learn that they did not need any sort of permits at all. I spent hours on the phone with state authorities seeking clarification because I didn't believe what the school engineers were telling me, but in the end it appeared that they were right.

Don't anybody read this and infer that they don't need a permit, but this one particular laboratory at one particular university apparently did not.

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

First of two simultaneous responses-- (2000)

Ted, is probably right. Universities are known have their own environmental departments and treatment plants. They are also very responsive and responsible because the university is also liable for lawsuits. Just like some chemicals, there are some nasty students too. Universities are careful. Having said that, Sushil still needs to check into it.

And then again, Ted, agencies probably are a little forgiving to schools because the amount of likely waste they produce compared to a single plating facility. Assume, they do not want to stifle the education.

Mandar Sunthankar
- Ft. Collins, Colorado

Second of two simultaneous responses-- (2000)

School labs are EXEMPT to a lot IF. That IF is the kicker.

I will bet two cups of coffee that a 30 gal tank would not meet the intent of the exception and will bet one cup that it does not meet the exepption requirements. You would have to check the CFR.

James Watts
- Navarre, Florida

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