Which welding process is best known for being able to weld through contamination such as rust and oil?

The process best known for its ability to weld through contamination such as rust and oil is Flux-Cored Arc Welding (FCAW). This welding method utilizes a tubular wire filled with flux, which helps to protect the weld pool from atmospheric contamination. The flux generates a shielding gas and provides slag to protect the weld pool, making it more forgiving of existing surface contaminants like rust, oil, and dirt compared to other welding methods.

FCAW is particularly advantageous in situations where the surface preparation may not be optimal because the flux can react with impurities, minimizing their adverse effects on the weld quality. This enables effective welding in various outdoor and industrial environments, where contamination is often present.

In contrast, other welding processes like MIG and TIG typically require cleaner surfaces as they rely on more straightforward shielding gas methods or precisely controlled welding environments to produce high-quality welds. Therefore, while they can be effective in clean applications, they are not as tolerant to contaminants as FCAW.