This article describes compounds developed to enhance the penetration of the gas tungsten arc welding (GTAW) process. Penetration-enhanced GTAW processes have been referred to variously as Flux TIG, A-TIG, and GTAW with a penetration-enhancing compound (PEC). In all cases, the process uses a material that is not a flux but rather an oxide or mixture of oxides. The productivity of traditional GTAW is limited for many applications because of low deposition rates, shallow penetration (typically 3 mm, or ? in.), or inconsistent penetration. Penetration-enhanced GTAW processes can increases weld penetration by as much as 300% and reduces heat-to-heat variation in penetration and distortion.