Usually Openair® plasma systems are supplied with compressed air as the assist gas. However, if an oxide layer is to be removed from surfaces, the assist gas is simply replaced with a mixture of gases and appropriate functional constituents. Forming gas, a mixture of nitrogen and hydrogen, is especially suitable for such plasma cleaning. The hydrogen is supplied in a non-critical, non-explosive mixture ratio (no greater than 5%).
The characteristics of the resulting forming gas plasmas differ completely from those of the usual Openair® plasma. Instead of incorporating oxygen in the surface of the material, it is securely removed by the plasma treatment. Even highly oxidized copper surfaces are bare again in a short period of time. This form of plasma cleaning leads to safe contact cleaning and therefore to reliably reproducible soldering and coating processes that are of fundamental importance for fuel cells and batteries.