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Left copper waterblock in vinegar too long?

post #1 of 3
Thread Starter 
So I ended up leaving a copper waterblock in vinegar+salt (so basically hydrochloric acid) for 18 hours. I'm getting conflicting results on google, where some say copper is a noble metal and will not dissolve. Others say that oxygen dissolves in the bath and that will corrode copper after the tarnish is removed.

All I know is that one block was left in for 4 hours longer than another (14 hours total), and on the one that was left in longer looks "powdered". I'd take a pic, but I'm away from home at the moment.

EDITMight have answered my own question:
Quote:
Any oxygen from air dissolved in the solution (or any hydrogen peroxide you add) will oxidize some of the copper on the bare metal surface in the solution. And this oxide will be promptly dissolved in this acidic solution

Edited by dr/owned - 3/30/13 at 9:19am
post #2 of 3
Does the powder come off? Is there any visual defects in the copper?

I haven't taken chem in a year, but remember a lab we had just like this. We took pennies and put a salt vinegar mix on them and observed how quickly they were cleaned. Then we let them.sit overnight until next class and they all turned green because they oxidized.in fact it sounds very similar to this http://www.chem.umn.edu/outreach/card-saltvincopper.html

So it has oxidized and you have a copper oxide layer on top. You might be just fine cleaning it off, but not with water, just a soft cloth. Not sure, though.

Edit: regarding your google results, both are not technically right. I'm on my phone so I can't give you a detailed explanation, but oxygen does not "dissolve" it is a gas, and the cooper did not dissolve either, the vinegar mix made it susceptible to reacting with the oxygen and moisture in the air. What I'm stumped on is whether it is a good idea to remove the powder as that is the copper oxide layer that built up from reacting with the air. So when you remove it, it will probably just come right back or it may not now that it's removed from the vinegar and does not have a catalyst (if the vinegar is a catalyst).
Edited by Dmz96 - 3/30/13 at 9:27am
    
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CPUMotherboardGraphicsRAM
Intel Core i5-3570K 3.4GHz Quad-Core Processor ASrock Z77E-ITX Mini ITX LGA1155 GALAXY GeForce GTX 670 4GB G.Skill Ares Series 8GB DDR3-1600  
Hard DriveHard DriveCoolingCooling
Western Digital Caviar Blue Corsair Neutron GTX 240GB Swiftech H220 Corsair AF120 
OSMonitorKeyboardPower
Windows 8 OEM Asus VE228H 21.5" Ducky Shine II (Purple) Silverstone ST55F-G (550watts) 
CaseMouseAudioOther
Caselabs Mercury  Cyborg R.A.T. 7 Albino Bose IE2 Earbuds TripTCC Backplate 
Other
Modeler's LEDs 
  hide details  
Reply
post #3 of 3
Thread Starter 
Unfortunately, rubbing does not remove whatever is going on with the surface. It looks like the "powder" is a highlighted contrast of the CNC tooling marks. I'm guessing some copper was removed, but probably not enough to make a cooling difference.

Remember that fish breathe underwater because oxygen dissolves in water. Same thing must happen with vinegar. It was oxidizing while under-vinegar and then the vinegar was removing it.

Moral of this story: don't leave your blocks soak overnight.
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