Author Topic: Copper in pbw turns dark?  (Read 448 times)

Offline trapae

  • Brewer
  • ****
  • Posts: 304
Copper in pbw turns dark?
« on: April 07, 2019, 06:16:40 PM »
 I left my copper immersion coil soaking in PBW for a couple days and many of the coils turned dark kind of blackish. Any one with more chemistry knowledge than me you know why?
I am a great believer in luck, and I find the harder I work, the more I have of it.

Offline Robert

  • Official Poobah of No Life.
  • *
  • Posts: 3912
Re: Copper in pbw turns dark?
« Reply #1 on: April 07, 2019, 06:56:07 PM »
I don't have the chemistry knowledge to explain in detail, but I know it's a corrosive effect of the alkaline cleaner, and any of them will do it given time.  I've had it happen -- green water and black immersion chiller.   A good soak in acid corrected it and restored the copper.  Try 50/50 distilled vinegar and water, or an acid cleaner.
Rob Stein
Akron, Ohio

I'd rather have questions I can't answer than answers I can't question.

Offline narcout

  • Senior Brewmaster
  • ******
  • Posts: 1966
  • Los Angeles, CA
Re: Copper in pbw turns dark?
« Reply #2 on: April 07, 2019, 07:38:25 PM »
Soaking copper in an alkaline solution will oxidize it. 

As Robert suggested, you should be able to remove the copper oxide with an acidic cleaner, but don't overdo it.
There's nothing left to dismantle; the house it just collapsed on itself.  - A. Savage

Offline trapae

  • Brewer
  • ****
  • Posts: 304
Re: Copper in pbw turns dark?
« Reply #3 on: April 07, 2019, 08:02:18 PM »
 Thanks, soaked it for 10 minutes and starsan and back to normal.
I am a great believer in luck, and I find the harder I work, the more I have of it.

Offline kramerog

  • Senior Brewmaster
  • ******
  • Posts: 1973
    • My LinkedIn page
Re: Copper in pbw turns dark?
« Reply #4 on: April 08, 2019, 01:50:27 PM »
I wasn't sure if my eyes were playing tricks on me, but my cooling water had a very light green hue after chilling the wort.  Now I know that my copper immersion chiller made it green.

Offline Robert

  • Official Poobah of No Life.
  • *
  • Posts: 3912
Re: Copper in pbw turns dark?
« Reply #5 on: April 08, 2019, 02:07:13 PM »
I wasn't sure if my eyes were playing tricks on me, but my cooling water had a very light green hue after chilling the wort.  Now I know that my copper immersion chiller made it green.
Wow, is that highly alkaline water?  I've only seen this effect when really overdoing the PBW.

BTW on this topic:  I normally don't use any cleaners on my IC.   Just rinse very thoroughly with hot water immediately after use.  This allows a passive oxide layer to form and remain on the copper, so it won't react with wort.  Best practice is to proceed this way, only cleaning with PBW if ever the IC is not immediately rinsed and some horrible stuff dries onto the surface.  Then let the oxide layer reform.  The IC should not be kept shiny, but allowed to grow dull like an old penny.
Rob Stein
Akron, Ohio

I'd rather have questions I can't answer than answers I can't question.

Offline kramerog

  • Senior Brewmaster
  • ******
  • Posts: 1973
    • My LinkedIn page
Re: Copper in pbw turns dark?
« Reply #6 on: April 08, 2019, 04:43:35 PM »
I wasn't sure if my eyes were playing tricks on me, but my cooling water had a very light green hue after chilling the wort.  Now I know that my copper immersion chiller made it green.
Wow, is that highly alkaline water?  I've only seen this effect when really overdoing the PBW.

BTW on this topic:  I normally don't use any cleaners on my IC.   Just rinse very thoroughly with hot water immediately after use.  This allows a passive oxide layer to form and remain on the copper, so it
The pH is only about 8.3. I only notice the green hue in my HLT, which I use to collect the cooling for later reuse.

Sent from my Moto Z (2) using Tapatalk