[trapae]

 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?

[Robert]

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.

[narcout]

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.

[trapae]

 Thanks, soaked it for 10 minutes and starsan and back to normal.

[kramerog]

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.

[Robert]

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.

[kramerog]

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.

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