Oerlikon Inertrod 420 description: INERTROD 420 is a ER 420 type solid TIG welding rod depositing a high C-13%Cr. Suitable for use mainly with Ar shielding gas. INERTROD 420 is used for many surfacing operations. INERTROD 420 is similar to INERTROD 410, but with higher chromium and carbon content, which increases the wear resistance.