Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy and magnetic measurements on thermally oxidized AISI 304 and AISI 316 stainless steels

► The surface roughness of the bare substrate influence the oxide layer growth. ► The oxide layer roughness follows power laws and belongs to universality class. ► At low growth temperature, the p–n heterojunction disappears in some places. ► SKPFM images allow the direct visualization of local corrosion sites. ► Presence of a magnetite phase in the outer iron rich layer of the oxide thin film. Thermally oxidized AISI304 and AISI316 stainless steels are studied by Atomic Force Microscopy, Scanning Kelvin Probe Force Microscopy (SKPFM) and Magneto-Optical Kerr effect as a function of their growth temperature. The surface roughness is a competition between the roughness of the bare substrate and the roughness resulting from the oxide layer growth. Cr oxide is present at some places on the surface at low growth temperature as shown by SKPFM. The observed decrease of surface potential with the oxide layer thickness indicates an effective protection against corrosion. Magnetic measurements demonstrate that the outer layer contains a magnetite phase (in-plane magnetization).