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Respirator recommendation for acid copper

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November 16, 2021

Q. Hi there- I'm an advanced hobbyist/ artist using a basic copper acid watts formula.
My bath is 40 gallons however in constant circulation. While the room has some ventilation I'm concerned that this winter gasses may build up more than usual.

Other than covering the tank when it's not in active use- Are there specific respirator filters I should be looking at? I understand that the sulfuric acid is not particularly volatile but I worry it might be slightly vaporizing?

In particular I've noticed a difference in the oxidation of finished copper items- exposed to the air in the studio they darken much faster than similar items kept at my home.

Any suggestions really appreciated!

Raphael Lyon
- Brooklyn New York

"Electroplating Engineering Handbook"
by Larry Durney
from Abe Books

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November 2021

A. Hi Raphael. It is true that plating shops tend to be very corrosive atmospheres, so I don't at all doubt that copper darkens quicker than in your home. You should probably try for some sort of local exhaust. Plastic exhaust ventilation systems are available, although very expensive, but even something as casual as a 4" round flexible duct for a clothes dryer connected to a small fan would help somewhat, and something in between would be great.

On the other hand, I don't think a respirator is needed. I'm no epidemiologist, but 50+ years in the plating industry tells me that if there is any excess morbidity even among those who work all day every day in the foul environments of old fashioned plating shops, it's not by enough to be obvious. Gloves and goggles seem much more important.

Luck & Regards,

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

November 17, 2021

Q. Thanks Ted! Yes definitely to the goggles and gloves. !
I have a window in the space and ventilation can be improved with a fan. I still wonder if I shouldn't be wearing a half mask 3M style respirator with an 'acid gas' filter when I'm pulling items in and out of the tank or polishing them with vinegar and peroxide. There's definitely some odors involved.

It's confusing to me how acid gas, which I imagine is responsible for corrosion, is even formed in the air -- but maybe just some of it diffuses off the tank surface?

I also have a zinc sulfate tank for zinc over copper plating too if that makes a difference. I zinc plate then heat in a small kiln to get a brass surface.

Anyway, good to know it's optional at least for the acid zinc.

Raphael Lyon [returning]
- Brooklyn New York

November 2021

A. Hi again. Two sources of "fumes" would be

• hydrogen bubbles which form on the metal during pickling & plating, which then race towards the surface and entrain some solution with a ginger-ale or champagne effect;
• vapor pressure / volatility of the solution evaporating into the air. In this case, the vapor pressure of sulfuric acid is quite low, but that of hydrochloric acid (which might be used in your acid zinc plating) is quite high. If that is the case you are probably smelling the zinc plating tank more than the copper plating tank.

You can certainly wear a respirator if you wish, but professional platers rarely do, and even then mostly only when doing chrome or cadmium plating.

A general principle of industrial ventilation is to try to exhaust as near as practical to the surface you are exhausting because the more the fumes mix with room air, the more air you need to exhaust to get rid of them. If you can hinge your tank covers along their back edges such that when you uncover the tanks the covers are vertical and comprise foot-tall (or so) walls at the back edge of your tanks, and you connect 4" dryer flex ducts in their centers, with 4" square computer fans somewhere in those ducts, or a kitchen exhaust fan on the wall, you can probably do a marginally effective exhaust ventilation job on two tanks for under a hundred dollars.

Luck & Regards,

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

November 17, 2021

thumbs up sign Thanks Ted! Always a font of information.

Raphael Lyon [returning]
- Brooklyn New York

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