Surface analysis techniques using electron microscopy for steel products are reviewed. The recent progress of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and focused ion beam （FIB） are presented with some applications to steel surfaces, coating layers and corrosion products.
Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS), and Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) are surface analysis techniques which provide atomic- and molecular-level surface chemical information. They are widely used for failure analysis, quality control, and research and development of advanced materials and devices. In this review, we overview the recent progress of the commercial apparatus, and also highlight their improved sensitivity and depth profiling capabilities. We also introduce their recent application in corrosion science.
Recently, passive film breakdown of Fe has been investigated in solutions of various anions by measuring the time required for breakdown, tbd and permeation of anions into the passive film using X-ray photoelectron spectroscopy. The results have been discussed on the basis of the hard and soft acids and bases (HSAB) principle. In previous study, the pitting and repassivation potentials of a passivated Fe electrode were measured in a borate buffer solution containing Cl－. The effects of added I－ on pit initiation and growth were discussed using electronprobe microanalysis and based on the HSAB principle. In this paper, the results of the previous investigation are interpreted by considerations of the recent work in more detail.
Reduction of the chloride ion ingress in concrete will be greatly improved by adding blast furnace slag fine powder to concrete. Its durability has, however, not been fully verified in actual corrosive environment. In addition, the possibility of reinforcing steels' corrosion has remained as ever; hence a technique for observing and predicting the internal corrosive environment needs to be established. In this study, exposure testing has been operated at a site near seashore to verify the durability of concrete mixed with ground granulated blast-furnace slag 6000. In the test, the apparent diffusion coefficient has been investigated and electrical potential of rebar in concrete has been telemetered with a monitoring system newly developed in this study. Main conclusions obtained in this study are as follows: [I] the apparent diffusion coefficients obtained from the specimens exposed for three years show the curve close to the prediction equation defined in the Standard Specification for Concrete Structures with changing the third term of the equation. ［II］ The monitoring system has allowed to observe corrosion potential in a long period and to monitor remotely the changes of corrosive environment over time.
The objective of this study is to clarify the preferential dissolution mechanism of a duplex stainless steel (DSS) at its corrosion potential (about －0.15 V vs.SHE) by means of Scanning Electrochemical Microscope (SECM) observation of the corrosion reactions on the ferritic phase (α phase) and the austenitic phase (γ phase) of a DSS, respectively. Probe electrode was fixed above α and γ each phase of DSS at corrosion potential in 1 mol/l HCl aqueous solution. Potential of the probe electrode was polarized toward noble direction, from －0.10 V to 1.4 V (SHE), at a potential scan rate of 20 mV/s, and probe current was measured. In a probe potential range of 0～0.70 V (SHE), anodic current due to hydrogen oxidation reaction could be detected. This anodic current was larger above γ phase than that above α phase. In a probe potential range of 0.70～1.2 V (SHE), anodic current due to Fe2+ oxidation reaction to Fe3+ could be detected. This anodic current was larger above α phase than that above γ phase. On the α phase, the anodic dissolution reaction occurred preferentially at the DSS corrosion potential, while on the γ phase, the cathodic reduction reaction of hydrogen ion occurred preferentially.