INFLUENCE OF THE SURFACE-CHEMISTRY ON THE WETTABILITY OF STAINLESS-STEEL

Degreasing with solvents, chemical etching, polishing, oxygen and argon plasma treatment and heating and drying produce stainless-steel surfaces with different amounts of organic contamination and 'bonded water'. The hydroxide/oxide layer of the passive film formed on stainless-steel foils is also affected by surface pretreatment. Electron spectroscopy for chemical analysis (ESCA) has been used to analyze the composition of the surface film formed after different cleaning procedures. Organic contamination on 304 stainless-steel foils can be reduced by a factor of five using various cleaning treatments. Wettability or surface energy measurements have been performed on the treated surfaces and it was found that the surface energy of the metal decays with the inverse of the contamination layer thickness. As these cleaning treatments lead to different oxide layers, it is concluded that the nature of the oxide layer is not the main parameter that determines the surface free energy of metals.