Used OCS solution at a 10:1 dilution ration heated to 150°F.  Cleaned gauges in ultrasonic for 3 minutes.  Parts appeared to be contaminant free. No rust preventative was used.  

Gauges were dried with ambient air and when cooled, they were placed in plastic bags.

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The ultrasonic cleaner is a non caustic, SCAQMD compliant chemistry.  This cleaner is used successfully in, and without damaging ultrasonic cleaning machines