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Mike,

I've used both hydrogen peroxide and CLR (brand name lime & rust 
remover). For a TEM-sized chiller, this took one bottle of CLR or 1 
Liter of 3% H2O2 (or 100 mL 30% H2O2). Circulate this for one to six 
hours, or even overnight if needed (sounds like that will be needed in 
your case), followed by flushing with 4-5 volumes of tap water.
This works well, and causes no damage to instrument chilling lines.
When I had a biofilm-sludge clogging problem, the vinegar trick worked. 
I used about 1 Liter of vinegar for this, followed by tap water.

Phil

On 11/23/2015 16:46 , Michael Giacomelli wrote:
> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> I recently discovered an old laser in storage.  Unfortunately the
> previous users had not drained the coolant lines, resulting in several
> years corrosion blocking the lines.  I flushed them out as best I
> could and found a grey metal slurry that was fairly thick in place of
> what was once the coolant.  Unfortunately, even with flushing I can't
> flow anything through the system using a normal thermotek chiller.
>
> Are there any options in this situation to unclog a laser?  Looking at
> the material in the line, its fairly diffuse and does not appear all
> that solid.  Is it possible to use something like a weak acid to
> dissolve any solid material blocking the line?  Or some other
> solvent/cleaner?
>
> Mike
>

-- 
Philip Oshel	
Microscopy Facility Supervisor
Biology Department
024C Brooks Hall
Central Michigan University
Mt. Pleasant, MI 48859
(989) 774-3576