Which metal is generally not suitable as packing material?

Chrome-steel is not typically used as packing material due to its specific properties that do not align well with the requirements for effective packing in most applications. Packing materials are generally chosen for their low weight, corrosion resistance, and ease of handling. Chrome-steel, while strong and durable, tends to be heavier and can corrode under certain conditions, making it less suitable for use where packing materials are necessary.

In contrast, aluminum, copper, and brass are common choices for packing due to their favorable characteristics. Aluminum is lightweight and corrosion-resistant, copper has good thermal conductivity while also resisting corrosion, and brass combines durability with a degree of flexibility, making them all more practical for packing purposes.