The classic material for water boxes has always been:

Cast iron has historically been a preferred material for water boxes primarily due to its excellent corrosion resistance and durability in various water conditions. Its ability to withstand high pressures and thermal variations makes it suitable for applications where it is constantly exposed to water. Cast iron's natural ability to dissipate heat efficiently also contributes to its effectiveness in heat exchange scenarios commonly seen in water boxes.

Moreover, cast iron is relatively inexpensive compared to other materials and can be easily cast into complex shapes, which is advantageous during manufacturing. Its high compressive strength further supports its use in heavy-duty applications, making it a reliable choice for water boxes that must endure operational stresses in power engineering systems. While other materials such as brass or low carbon steel have specific applications, cast iron remains the classic choice for water boxes due to its unique properties suited for holding and managing water effectively in engineering systems.