Daniel Wallinder

Eis and XPS study of surface modification of 316LVM stainless steel after passivation

Abstract The effects of surface finish, nitric acid passivation and ageing in air on corrosion resistance of 316LVM stainless steel in 0.5% H 2 SO 4 have been investigated by EIS, potentiodynamic polarization measurements and XPS. The results indicate that a smoother surface exhibits to a higher corrosion resistance. The effectiveness of the passivation treatment strongly depends on nitric acid concentration, passivation time and temperature. The passivation treatment significantly increases the corrosion resistance due to a high Cr content in the passive film and increased film thickness. Ageing after passivation increases the corrosion resistance whereas ageing before passivation has little effect.

Influence of Hydrogen in Iron and in Two Stainless Steels on Aqueous and Gaseous Corrosion

The influence of hydrogen in Fe, 301 stainless steel (SS 301), and Avesta 353MA on corrosion resistance in aqueous solutions was studied. The oxidation kinetics of uncoated and Pt-coated Fe was also investigated in O-2 at 500 and 700degreesC. Electrochemical and weight loss measurements were used to evaluate the corrosion resistance in aqueous solutions, and the high-temperature oxidation rate was determined by measuring the pressure decrease in a closed volume. Observations of a high dissolution rate of Fe and SS 301 in deionized water, as well as a high oxidation rate in O-2, can be explained by an increased metal cation transport in the oxide film induced by hydrogen in the metal. However, hydrogen up to a certain concentration in Avesta 353MA was found to increase the resistance to localized corrosion in chloride solution. Pt coating on Fe was found to decrease the oxidation rate and improve scale adherence. The presented results are discussed in view of recent findings of balanced metal cation and oxygen anion transport in protective metal oxides.

Hydrogen in chromium : influence on corrosion potential and anodic dissolution in neutral NaCl solution

The influence of hydrogen charging, outgassing, pickling and passivation of mechanically polished chromium was investigated with respect to corrosion potential and anodic dissolution in 0.3 M NaCl ...

Electrochemical investigation of pickled and polished 304L stainless steel tubes

The influence of two pickling methods and mechanical polishing on polarization resistance, passive current density and break-down potential of 304L tubes was investigated by EIS and potentiodynamic measurements in 0.05 M H2SO4 + 0.05 M NaCl solution. The electrochemical cell was specially designed to separately measure outer and inner surfaces of tubes. The results demonstrated that the outer and inner surfaces of tubes could be separately evaluated by the electrochemical measurements using the cell configuration. Differences in the electrochemical behavior were observed between pickled and polished tubes, between the inner and outer surface of tubes, and between the two pickling methods.

Reliable Strategy for Analysis of Complex Biosensor Data

When using biosensors, analyte biomolecules of several different concentrations are percolated over a chip with immobilized ligand molecules that form complexes with analytes. However, in many cases of biological interest, e.g., in antibody interactions, complex formation steady-state is not reached. The data measured are so-called sensorgram, one for each analyte concentration, with total complex concentration vs time. Here we present a new four-step strategy for more reliable processing of this complex kinetic binding data and compare it with the standard global fitting procedure. In our strategy, we first calculate a dissociation graph to reveal if there are any heterogeneous interactions. Thereafter, a new numerical algorithm, AIDA, is used to get the number of different complex formation reactions for each analyte concentration level. This information is then used to estimate the corresponding complex formation rate constants by fitting to the measured sensorgram one by one. Finally, all estimated rate constants are plotted and clustered, where each cluster represents a complex formation. Synthetic and experimental data obtained from three different QCM biosensor experimental systems having fast (close to steady-state), moderate, and slow kinetics (far from steady-state) were evaluated using the four-step strategy and standard global fitting. The new strategy allowed us to more reliably estimate the number of different complex formations, especially for cases of complex and slow dissociation kinetics. Moreover, the new strategy proved to be more robust as it enables one to handle system drift, i.e., data from biosensor chips that deteriorate over time.