Which material must not be used in refrigeration systems containing halogenated refrigerants?

Magnesium is not suitable for use in refrigeration systems containing halogenated refrigerants due to its reactivity. When magnesium comes into contact with halogenated refrigerants, it can lead to corrosive reactions that compromise the integrity of both the refrigerant and the system components. These reactions can result in the release of toxic gases and a risk of fire, making magnesium an unsafe choice for these applications.

In contrast, aluminum, copper, and steel are commonly used materials in refrigeration systems. They offer good durability and resistance to corrosion when properly treated, allowing for safe and efficient operation in various refrigeration applications, including those that use halogenated refrigerants. Understanding the appropriate materials for refrigeration systems ensures system reliability and safety.