Plasma-Assisted Surface Activation
A physical process in a vacuum where organic residues are removed and polar groups are generated by a gas plasma. It maximizes wettability and adhesion for subsequent process steps.
Plasma activation is basically intensive cleaning and roughening of the surface at the molecular level. It burns off organic residues like oil or grease completely, which you can't get off with a rag. The plasma also makes the surface chemically active, so adhesives or coatings adhere really well afterwards. If you skip this before welding, you'll quickly get pores in the weld or the filler metal just 'beads' off. The surface must be clean and dry for this; the plasma itself takes care of the rest. Afterwards, just quickly check that there are no streaks or residues left, then it's fine.