Cast irons are alloys which typically have over 2% carbon plus 1-3% silicon and are difficult to weld. Electrodes with a high percentage of nickel are commonly used to repair cast iron. Nickel is very ductile, making it a good choice to weld on cast iron, which is very brittle. RepTec Cast 1 and RepTec Cast 3 are the Lincoln Electric electrodes designed for welding cast iron.