The chemical reaction between clearcoat and catalyst begins when?

• A. they are combined
• B. they are heated
• C. they are sprayed
• D. they are exposed to air

Answer: (A)

In this type of coating, curing is a chemical process that starts when the two parts are combined. The clearcoat resin and the catalyst (the curing agent) are kept separate until you mix them; the catalyst remains inactive on its own. Once mixed, the reactive groups in the resin and the catalyst begin to react with each other, forming new bonds and creating a cross-linked polymer network. That cross-linking converts the liquid coating into a solid, durable film.

Heating can speed up this reaction after mixing, and spraying is simply how you apply the already-mixed coating to the surface. Exposing to air isn’t what starts the chemical curing in a two-part system like this, though air can influence drying or evaporation around the film. So the initiation of the curing reaction happens at the moment the components are combined.