Cast iron parts that are not subject to high heat or excessive pressure are readily repaired with metal-based epoxies. Metal-based epoxies are available in either one or two parts. A one-part epoxy cures when exposed to air, and a two-part epoxy needs to be mixed to cure. Both types of metal-based epoxy harden to a steel-like strength that will provide a semi-permanent to permanent repair on cast iron. The permanence of the repair will depend on the cleanliness of the cast iron crack and the proper application of the metal-based epoxy.
Put on your safety glasses and leather work gloves.
Attach the 4.5-inch wire wheel to the 4.5-inch angle grinder and clean the cracked area of the cast iron with the 4.5-inch wire wheel. You need to remove all contaminants, including paint, from the surface of the cast iron.
Wipe the cleaned area of the cast iron with a clean rag to remove the dust created by the 4.5-inch wire wheel. If you are using a one-part metal-based epoxy, apply solvent to the rag and then wipe down the crack in the cast iron.
Mix equal parts of the two-part epoxy until the mixed epoxy forms one solid colour throughout. Skip this step if you are using a one-part metal-based epoxy.
Press the mixed two-part epoxy into the crack or apply the one-part epoxy into the cast iron crack with the putty knife.
Allow the metal-based epoxy to cure for the time specified by the epoxy usage instructions before using the repaired cast iron part.