To use cast iron repair epoxy, clean and scuff the application area, mix both parts of the epoxy, apply immediately to the repair area and allow to dry. After drying, the epoxy can be tapped, sawed, filed or otherwise machined in most of the same ways as cast iron.
The cleaning and scuffing step is the most important aspect of the entire cast iron epoxy repair process. If the cast iron is covered in even small amounts of paint, dirt, grease or grime, the epoxy cannot adhere properly, and the resulting repair is weak and fragile. A thorough cleaning removes any material that prevents the epoxy from adhering, while scuffing the cast iron strengthens the repair by increasing the surface area to which the epoxy can adhere.
Mixing the two parts of the epoxy immediately before application is essential to avoid early drying. While most cast iron repair epoxies take up to six hours to fully dry, they begin setting immediately after mixing. A partially dry epoxy is not able to fully adhere to the cast iron, and the resulting repair is weakened. Some cast iron repair epoxies make the mixing process simpler by keeping both parts of the epoxy in separate chambers within a single container, and automatically mixing them during application.