Permitted (O)
– Carbon steel
– Stainless steel
– Aluminum
– Other nonmetallic materials such as PTFE are permitted (if they will not break down)
Source: http://www.ashrae4greenville.com/resources/Newsletter/2014/Intro-to-Ammoni-Refrigeration.pdf
Not permitted (X)
– Copper and copper alloys such as brass are prohibited (but allowed for bearing materials)
– Zinc (in continuous contact with ammonia)
– Non-metallic materials that degrade upon exposure
– Other nonmetallic materials such as PTFE are permitted (if they will not break down)
Source: http://www.ashrae4greenville.com/resources/Newsletter/2014/Intro-to-Ammoni-Refrigeration.pdf