Why Can’t Copper Be Used with Ammonia Evaporator?

Copper cannot be used with an ammonia evaporator because ammonia is not compatible with copper and copper alloys in refrigeration service.

Ammonia can react with copper-based materials and cause material degradation over time. In an evaporator, that creates a reliability and safety problem because the coil must withstand refrigerant pressure and long-term thermal cycling. For this reason, ammonia systems normally use steel tubes or stainless steel tubes instead of copper.

In practice, the main concerns are:

1. Material compatibility
Ammonia systems are designed around ferrous materials because they are much more suitable for R717 service. Copper is generally avoided in the refrigerant circuit.

2. Risk of corrosion and damage
Using the wrong material can shorten equipment life and increase the chance of leaks or failures.

3. System safety
Ammonia refrigeration is often used in industrial plants, where safe and durable material selection is critical. That is why designers choose steel-based construction for evaporators, vessels, and piping.

4. Industry standard practice
In ammonia evaporators, the common combination is steel tube with aluminum fins, not copper tube with aluminum fins.