Surface analysis for corrosion study was reviewed. For the study, the in-situ analysis was desired to describe the real feature. Light i.e., electromagnetic wave from gamma rays to infrared light has been used for the in-situ measurement of the corroded surface, although various ideas should be introduced for the study. For the application of the electromagnetic waves, a suitable window material and a suitable distance between the window and specimen surface depending on the properties of the wave must be selected. Electron spectroscopy including X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) is not applicable for the in-situ study and, however, it is very available for the corrosion study from the following points; elemental analysis, state analysis of the element, and microscopic analysis. In future, the tip enhance Raman scattering (TERS) for which the scanning probe microscopy (SPM) is combined with the surface enhanced Raman scattering (SERS) may be useful for the in-situ corrosion study.
Synchrotron radiation beam, which can be used as diffraction, X-ray absorption fine structure, imaging, photoelectron spectroscopy, etc., has an advantage of ultra-bright, highly-directional, and so forth in comparison with conventional X-ray equipment. Therefore, its application has been expanded to various metal corrosion phenomena such as atmospheric corrosion of steels, the influence of alloying elements on the formation and structure of rusts of weathering steels, the underpotential deposition behavior of Pb on Ni electrode, the non-destructive in-depth analysis of the passive film of stainless steel, etc. In contrast, neutron beam, which can be used as neutron diffraction, small angle neutron scattering, neutron imaging, etc., has unique properties such as high transmittance and high sensitivity to hydrogen and water. From these features, it has been applied to metal corrosion researches such as the change of average size and volume fraction of weathering steel rusts during wet/dry cycles, the direct observation of water motion under blister of under-film corroded steels, etc.
In this paper, X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) were applied to investigate passive films formed on aluminum alloy in 0.5 kmol m－3 H3BO3/0.05 kmol m－3 Na2B4O7 with different metal cations. The metal cation is classified by metal cation hardness, X, which are calculated based on the concept of hard and soft acids and bases (HSAB) of the acid and base in Lewis’s rule. From XPS analysis, the metal cations with X＞4 were incorporated in passive films. The area-selected surface analysis of AES was also introduced.
Surface analyses are important in R&D of aluminum products because of high plastic forming performances of aluminum alloys. In this paper, three examples of surface analyses of aluminum are shown to demonstrate that statistical data processing, appropriate calibration and pretreatment of samples are essential to achieve real pictures of surfaces. First example is an evaluation of interface adhesion between a hard coating and aluminum alloy in nano-indentation method. Second example shows how to obtain two dimensional distribution of oxide layer thickness using a calibration line in EPMA. In the final example, oxide and hydroxide films are analyzed by FT-IR and GD-OES.
To improve sample analysis efficiency and equipment's cost performance for scientific instruments users, highthroughput non-destructive instruments which working in atmosphere condition without need for sample preparation, are highly recommended. In this work, we will introduce some instruments, suitable for the quick “Screening test”, and focusing on the latest surface analysis instrument, with some applications.
A part of copper surface changes from metallic luster to brown at an early stage of immersion under water. We term this brown film “initial film” and investigate the effect of silica and chloride ion in water on the formation of the initial film. An expansion of initial film after prolonged immersion depends on the water composition. A high concentration of chloride ion in water increases the area of initial film, whereas a high concentration of silica inhibits formation of the initial film. Cathodic reductions for copper tubes with an initial film revealed that the chloride ion acted as an accelerator of an initial film formation. The initial film of copper formed in the water containing silica and chloride ion was ascertained to consist of cuprous oxide and silicate containing siloxane bonds by FT-IR analysis.
One of the reasons why under-film corrosion occurs in the painting steel structure, is that repainting is performed although the rust still remains at the base material adjustment. Firstly we observed the rust of corroded steel sheet which is prepared by the Salt Spray Test (SST) before painting. The appearance of the specimen which is performed the base material adjustment after SST, is classified into bright area, dark area, and the steel exposed area. As a result of corrosion tests after the painting, it is confirmed that the under-film corrosion occurs in the dark area and the neighborhood.
The objective in this study was to clarify the effect of electrodeposited Ca film on hydrogen entry behavior into API-X65 by measurements of hydrogen content and an electrochemical hydrogen permeation technique in Ca(OH)2 and NaOH solutions under constant current cathodic hydrogen charging. As a result, hydrogen content in the steel cathodically charged in Ca(OH)2 solution was larger than that in NaOH solution, which was attributed to the formation of Ca film. And hydrogen permeation efficiency on the area where electrodeposited Ca film didn't exist (reaction part) was measured by the electrochemical hydrogen permeation technique. From 0 to 40% of electrodeposited Ca film coverage, it was clarified that hydrogen permeation efficiency increased and hydrogen entry was enhanced at the reaction part. It was clarified that hydrogen permeation efficiency decreased and hydrogen entry was inhibited at the reaction part when the electrodeposited Ca film coverage was more than 40%.
Monitoring study for an existing bridge carried out to confirm the validity of the corrosive environment predictions before construction, by reason of that the weathering steel type and anticorrosion method for the target bridge were selected from the corrosive environment estimation before construction. This paper reports the corrosive environment monitoring results in girders for an existing weathering steel bridge by exposure tests, in a program designed for 1, 3 and 5 year exposure time periods, using attachable small test pieces. From the results of exposure tests, the validity of the corrosive environment predictions before construction is confirmed. However, it is found that the influence of structural form with bridge and climate change is large to evaluate the corrosion durability on weathering steel bridges over 100 years.
To improve the corrosion resistance of the duplex stainless steels, great efforts have been made to clarify the pitting initiation in order to suppress the pitting corrosion which is one of the most hazardous forms of the stainless steels' failure. In general, manganese sulfide (MnS) is known to act as the pitting initiation in environments containing chloride ions. Thus, the inclusion control is essential for the development of duplex stainless steels with high corrosion resistance. In this study, the effects of the inclusion control by Ta addition on the pitting corrosion resistance of the duplex stainless steels were investigated. The Ta-bearing duplex stainless steels exhibited the remarkably high pitting corrosion resistance compared to that of the duplex stainless steels without Ta. The Ta-bearing duplex stainless steel contains no MnS inclusion but (Ta, Mn)-oxysulfide. This indicates that sulfur is stabilized as (Ta, Mn)-oxysulfide instead of MnS which is the typical pitting initiation. Ta addition to the super duplex stainless steel improved the pitting corrosion resistance because MnS, which acts as a pitting initiation, was modified to the electrochemically-stable Ta-containing inclusions.
Duplex stainless steel has high corrosion resistance and high strength. However, pitting corrosion occurs in duplex stainless steel in the solution containing high concentrated chloride ion. Pitting corrosion is caused by dissolution of inclusion, such as manganese sulfide (MnS). In previous study, the pitting corrosion resistance of the super duplex stainless steels including 20 ppmS could improve by Ta addition in the steels. In this study, we investigated the effect of addition of Ta on pitting corrosion behavior in standard duplex stainless steels including 10 ppm S. In conclusion, we observed that pitting corrosion resistance of standard duplex stainless steels could improve by addition over 0.06 mass% addition of Ta.
Attempts have been made to clarify an effect of acetic acid in hydrogen peroxide solution on corrosion behavior of welded aluminum alloy. The corrosion mass loss and polarization curve measurements have been carried out to obtain relationship between the acetic acid in hydrogen peroxide solution and electrochemical behavior of the 5254 aluminum specimen which was MIG-welded with 5654 aluminum alloy wire. It is found that the addition of 100ppm acetic acid to a 30%hydrogen peroxide solution accelerated corrosion of the welded 5654 specimen, which is considered from the electrochemical point of views such as the increasing hydrogen ions and decreasing the polarization resistance.