Here's a project summary from Hobart's Tubular Wire Division research developments of adding an additive to the shielding gas to reduce the amount of weld metal diffusible Hydrogen... This is achieved by adding fluorine gas, in the form of carbon tetrafluoride (CF4) to the shielding gas for gas-shielded welding processes (FCAW, GMAW, MCAW)...
For example; Rutile-type FCAW electrodes typically contain a limited amount of solid fluorides in the core; i.e. , an amount that will provide an acceptable balance of mechanical properties, weld metal hydrogen and improved operability...
As a consequence, there are no flux-cored electrodes currently on the market which offer superior mechanical properties, very low diffusible hydrogen (consistently less than 4 ml/100 gm of weld metal) and excellent operability... There's more in this .pdf:
http://www.nsrp.org/6-Presentations/Weld/050812_Hobart_Tubular_Wire_Division_Project_Summary.pdfAn interesting summary indeed!
Respectfully,
Henry