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Characterization (topography, chemical composition, wettability) of unmodified and modified surfaces

Topography measurements on unmodified surfaces have been realised by UGINE&ALZ using Interferometric and Atomic Force Microscopes. For 2R finish (bright annealing), the average roughness Ra is of the order of 0.04µm and the total roughness Rt is of the order of 1-1.5µm.As for 2B finish, Ra is of the order of 0.1µm and Rt is around 2µm. Moreover, using AFM allowed to determine the approximate grain boundaries depth (about 0.5µm) and width (about 1 µm), as well as the grain roughness Ra (roughness without taking into account the grain boundaries, which is roughly about 50nm), of an annealed-pickled (2B) surface.

Wettability measurements made by UGINE&ALZ show that the modified surfaces can be classified, in term of contact angle values, in the order: SiOx < implantation of SiF+ ions < DLC < Ni-P-PTFE. As far the surface energy is concerned, the order is the following: SiOx > implantation of SiF+ ions > DLC > Ni-P-PTFE.

XPS results highlight the fact that the passive film on the 2B finish is thicker and contains more chromium than the one on the 2R finish, whereas such finishes have a similar contaminated film thickness. As for the alkaline detergent cleaning, it leads to a decrease in both the iron / chromium ratio and the passive film and contaminated film thickness.

Reported by

Ugine & ALZ, Arcelor Group
UGINE&ALZ Research Centre of Isbergues
62330 Isbergues