Effect of atmospheric microwave plasma treatment on organic lubricant on a metallic surface

Coaxial injection microwave excited plasma torch, operating at atmospheric pressure has been tested to treat greased metallic surfaces. The treatment conditions were controlled using optical emission spectroscopy. The plasma treatment was carried out using argon plasma, with argon or oxygen in the periphery. The effect of plasma treatment on the grease was evaluated, using gravimetric analysis by weighing the sample before and after treatment, surface energy and X-ray photoelectron spectroscopic measurements. Initial period of treatment yielded etching of the grease, but, later on, the grease stabilized forming polymeric films, independent of the gas present in the periphery. The etching behavior was explained by different mechanisms involved in the plasma grease surface and sub-surface interactions.