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Technical Consultation of the International Space Station (ISS) Internal Active Thermal Control System (IATCS) Cooling Water ChemistryThe Internal Active Thermal Control System (IATCS) coolant exhibited unexpected chemical changes during the first year of on-orbit operation following the launch and activation in February 2001. The coolant pH dropped from 9.3 to below the minimum specification limit of 9.0, and re-equilibrated between 8.3 and 8.5. This drop in coolant pH was shown to be the result of permeation of CO2 from the cabin into the coolant via Teflon flexible hoses which created carbonic acid in the fluid. This unexpected diffusion was the result of having a cabin CO2 partial pressure higher than the ground partial pressure (average 4.0 mmHg vs. less than 0.2 mmHg). This drop in pH was followed by a concurrent increasing coolant nickel concentration. No other metal ions were observed in the coolant and based on previous tests, the source of nickel ion was thought to be the boron nickel (BNi) braze intermetallics used in the construction of HXs and cold plates. Specifically, BNi2 braze alloy was used for the IATCS IFHX and BNi3 braze alloy was used for the IATCS Airlock Servicing and Performance Checkout Unit (SPCU) HX and cold plates. Given the failure criticality of the HXs, a Corrosion Team was established by the IATCS CWG to determine the impact of the nickel corrosion on hardware performance life.
Document ID
20050217112
Acquisition Source
Langley Research Center
Document Type
Technical Memorandum (TM)
Authors
Gentz, Steven J. (NASA Langley Research Center Hampton, VA, United States)
Rotter, Hank A. (NASA Johnson Space Center Houston, TX, United States)
Easton, Myriam (Aerospace Corp. El Segundo, CA, United States)
Lince, Jeffrey (Aerospace Corp. El Segundo, CA, United States)
Park, Woonsup (Aerospace Corp. El Segundo, CA, United States)
Stewart, Thomas (Aerospace Corp. El Segundo, CA, United States)
Speckman, Donna (Aerospace Corp. El Segundo, CA, United States)
Dexter, Stephen (Delaware Univ. Newark, DE, United States)
Kelly, Robert (Virginia Univ. Charlottesville, VA, United States)
Date Acquired
September 7, 2013
Publication Date
September 1, 2005
Subject Category
Chemistry And Materials (General)
Report/Patent Number
NESC-RP-05-71/04-018-E
L-19174
NASA/TM-2005-213918
Funding Number(s)
OTHER: 104-08-43
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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