What is a key requirement of a two-component coating that differentiates it from a single-component coating?

A critical requirement that differentiates a two-component coating from a single-component coating is the need to mix a hardener with the base. In two-component coatings, the hardener chemically reacts with the base to initiate the curing process, resulting in a durable and resilient finish. This reaction can significantly enhance the mechanical properties and chemical resistance of the coating, making it ideal for challenging environments.

In contrast, single-component coatings are ready to use without the need for mixing, relying on air exposure or heat to cure. Therefore, the requirement for a hardener and the associated mixing process are fundamental aspects of two-component coatings, making this choice the correct answer.