J. Duchoslav

X-ray photoelectron spectroscopy of the effects of Ar+ ion sputtering on the nature of some standard compounds of Zn, Cr, and Fe

X-ray photoelectron spectroscopy combined with Ar+ ion etching is a powerful concept to identify different chemical states of compounds in depth profiles, important for obtaining information underneath surfaces or at layer interfaces. The possibility of occurring sputter damage is known but insufficiently investigated for corrosion products of Zn-based steel coatings like ZnCr. Hence, in this work reference materials are studied according to stability against ion sputtering. Indeed some investigated compounds reveal a very unstable chemical nature. On the basis of these findings the reliability of depth profiles of real samples can be rated to avoid misinterpretations of observed chemical species.

XPS investigation on the surface chemistry of corrosion products on ZnMgAl-coated steel

In this work, a novel evaluation strategy for the X-ray photoelectron spectroscopy (XPS) chemical assessment is proposed to identify the corrosion products formed on the surface of hot-dip galvanized ZnMgAl coatings after exposure to standardized salt spray tests. The experiments demonstrate that the investigated system exhibits a problematic differential charging behavior between the different compounds, an effect which cannot be fully compensated for by the flood gun of the XPS system, making a reliable evaluation of the individual spectra impossible by using standard evaluation and fitting methods. For that reason, a new effective approach—taking the different charge shifts into account—was implemented and its reliability experimentally verified on model mixtures of assumed corrosion products with known composition. With this new approach, the chemical surface composition of an industrial sample of a corroded ZnMgAl coating was revealed and discussed in order to clearly demonstrate the potential of the proposed method for future corrosion studies.

Nanoscale surface analysis on second generation advanced high strength steel after hot dip galvanizing

AbstractSecond generation advanced high strength steel is one promising material of choice for modern automotive structural parts because of its outstanding maximal elongation and tensile strength. Nonetheless there is still a lack of corrosion protection for this material due to the fact that cost efficient hot dip galvanizing cannot be applied. The reason for the insufficient coatability with zinc is found in the segregation of manganese to the surface during annealing and the formation of manganese oxides prior coating. This work analyses the structure and chemical composition of the surface oxides on so called nano-TWIP (twinning induced plasticity) steel on the nanoscopic scale after hot dip galvanizing in a simulator with employed analytical methods comprising scanning Auger electron spectroscopy (SAES), energy dispersive X-ray spectroscopy (EDX), and focused ion beam (FIB) for cross section preparation. By the combination of these methods, it was possible to obtain detailed chemical images serving a better understanding which processes exactly occur on the surface of this novel kind of steel and how to promote in the future for this material system galvanic protection. FigureThe image shows an Auger mapping of a hot dip galvanised TWIP steel after removing the surface oxides by Ar sputtering. The shown signal contains intensity information based on topography and work function and elemental distribution of Mn, Fe and Zn shown in blue, green and red

Nonlinear imaging of surfaces with confocal and interferometric SHG microscopy using a broadband 1550 nm fs-fiber laser

Confocal SHG (cSHG) microscopy and interferometric SHG (iSHG) microscopy open the opportunity to study non-destructively the symmetry of surface and interface structures of materials. The motivation for building the current set-up, operated with a turn-key 1550 nm fs-fiber laser system, can be found in the need of new noninvasive methods for the investigation of metal oxides and corrosion products, as e.g. found below painted steel surfaces [1] or on hot-dip galvanized Zn coatings on steel sheets.