Interface analysis, corrosion

Optical Techniques. The most important tool in a museum laboratory is the low power stereomicroscope. This instmment, usually used at magnifications of 3—50 x, has enough depth of field to be useful for the study of surface phenomena on many types of objects without the need for removal and preparation of a sample. The information thus obtained can relate to toohnarks and manufacturing techniques, wear patterns, the stmcture of corrosion, artificial patination techniques, the stmcture of paint layers, or previous restorations. Any art object coming into a museum laboratory is examined by this microscope (see Microscopy Surface and interface analysis). 

X-Ray Emission and Fluorescence. X-ray analysis by direct emission foUowing electron excitation is of Hmited usefulness because of inconveniences in making the sample the anode of an x-ray tube. An important exception is the x-ray microphobe (275), in which an electron beam focused to - 1 fim diameter excites characteristic x-rays from a small sample area. Surface corrosion, grain boundaries, and inclusions in alloys can be studied with detectabiHty Hmits of -- 10 g (see Surface and interface analysis). 

Chemical appHcations of Mn ssbauer spectroscopy are broad (291—293) determination of electron configurations and assignment of oxidation states in stmctural chemistry polymer properties studies of surface chemistry, corrosion, and catalysis and metal-atom bonding in biochemical systems. There are also important appHcations to materials science and metallurgy (294,295) (see Surface and interface analysis). 

Can the required data be acquired Can the desired areas of interest (appropriate interface or corrosion area) be identified for analysis Is data acquisition fast enough to generate desired data in reasonable time for allowable cost Can contamination mask the desired signals Is the appropriate type of data being taken ... 

Mellott, N. P., Brantley, S. L., Hamilton J. P. Pantano, C. G. (2001) Evaluation of surface preparation methods for glass. Surface and Interface Analysis, 31, 362-68. Mellott, N. P. Pantano, C. G. (2009). Multicomponent almninosilicate glass mechanisms of acid corrosion and surface layer formation. Journal of Non-Crystalline Solids, Submitted Manuscript. 

H. H. Sun, H. W. Wang,D. Chen,N. H. MaandX. F. Li, Conversion-coating treatment applied to in situ TiB2p reinforced A1 Si-alloy composite for corrosion protection . Surface and Interface Analysis, 40, 1388 (2008). 

Muster TH, Lau D, Wrubel H, Sherman N, Hughes AE, et al. (2010) An investigation of rare earth chloride mixtures combinatorial optimisation for AA2024-t3 corrosion inhibition Surface and Interface Analysis, 42,170-174. 

Elamdy, A.S., Beccaria, A.M., and Traverso, R, Corrosion protection of aluminium metal-matiix composites by cerium conversion coatings. Surface and Interface Analysis, 2002. 34(1) 171-175. 

Davis, G. D., Moshier, W. C. and Aheam, J. S. 1987. Corrosion of aluminum in dilute sulfate-solutions studies by surface behavior diagrams. Surface and Interface Analysis,... 

Watts JF (1988) Surf Interf Anal 12 497 Watts JF (2009) Adhesion science and technology. In Riviere JC, Myhra S (eds) Handbook of surface and interface analysis methods for problem solving. CRC Press, Boca Raton, pp 5651-5656 Watts JF (2010) Role of corrosion in the failure of adhesive joints. In Richardson JA et al (eds) Shreir s corrosion, vol 3. Elsevier, Amsterdam, pp 2463-2481 Watts JF, Wolstenholme J (2003) An introduction to surface analysis by electron spectroscopy. Wiley, Chichester... 

Professor Marcus is currently president of the European Federation of Corrosion, chairman of the EFC Working Party on Surface Science and Mechanisms of Corrosion and Protection, chairman of the International Steering Committee for the European Conferences on Applications of Surface and Interface Analysis, and chairman of the Scientific and Technical Committee of CEFRACOR (Centre Fran ais de lAnticorrosion). He is the former chairman of the Corrosion, Electrodeposition and Surface Treatment, and of the Electrochemical Materials Science divisions of the International Society of Electrochemistry. 

Electric Breakdown in Anodic Oxide Films Physics and Applications of Semiconductor Electrodes Covered with Metal Clusters Analysis of the Capacitance of the Metal-Solution Interface. Role of the Metal and the Metal-Solvent Coupling Automated Methods of Corrosion Measurement... 

Time Constant Analysis, r is the relaxation time of the corrosion process and is dependent on the dielectric properties of the interface. r is given by r = R P, but can be measured independently r = wz"max Since and P vary with surface area in exactly opposite fashion, r (or wzBmax) should be independent of surface area. To verify that this is indeed the case, we examined the corrosion of N80 steel in uninhibited 15% HC1 at 65 C. With increasing exposure time, we observed a continuous decrease in R (hence an increase in corrosion rate) and a concomitant increase in P. And, as expected, wz"max did not vary at all (see Figure 8). 

Aircraft turbines in jet engines are usually fabricated from nickel-based alloys, and these are subject to combustion products containing compounds of sulphur, such as S02, and oxides of vanadium. Early studies of the corrosion of pure nickel by a 1 1 mixture of S02 and 02 showed that the rate of attack increased substantially between 922 K and 961 K. The nickel-sulphur phase diagram shows that a eutectic is formed at 910 K, and hence a liquid phase could play a significant role in the process. Microscopic observation of corroded samples showed islands of a separate phase in the nickel oxide formed by oxidation, which were concentrated near the nickel/oxide interface. The islands were shown by electron microprobe analysis to contain between 30 and 40 atom per cent of sulphur, hence suggesting the composition Ni3S2 when the composition of the corroding gas was varied between S02 02 equal to 12 1 to 1 9. The rate of corrosion decreased at temperatures above 922 K. 

Dynamic SIMS is used for depth profile analysis of mainly inorganic samples. The objective is to measure the distribution of a certain compound as a function of depth. At best the resolution in this direction is < 1 nm, that is, considerably better than the lateral resolution. Depth profiling of semiconductors is used, for example, to monitor trace level elements or to measure the sharpness of the interface between two layers of different composition. For glass it is of interest to investigate slow processes such as corrosion, and small particle analyses include environmental samples contaminated by radioisotopes and isotope characterization in extraterrestrial dust. 

The surface of a solid sample interacts with its environment and can be changed, for instance by oxidation or due to corrosion, but surface changes can occur due to ion implantation, deposition of thick or thin films or epitaxially grown layers.91 There has been a tremendous growth in the application of surface analytical methods in the last decades. Powerful surface analysis procedures are required for the characterization of surface changes, of contamination of sample surfaces, characterization of layers and layered systems, grain boundaries, interfaces and diffusion processes, but also for process control and optimization of several film preparation procedures. 

Corrosion necessarily involves a reaction of a material with its environment at a solid-gas, solid-liquid or solid-solid interface. One might think, therefore, that corrosion scientists would be among the most enthusiastic users of surface analytical techniques, which by their nature examine such interfaces (5). However, as McIntyre (5) notes about XPS, "the impact on corrosion science has been rather modest," and according to an editorial in Corrosion (6), any significance of surface science in solving corrosion problems is not obvious to many corrosion professionals and plant operators. Recent advances in surface science techniques have increased the usefulness of these methods in applied areas such as corrosion. To understand the current role of surface analysis in corrosion research and problem solving, it is necessary to know about the many forms of corrosion and the advantages and limitations of surface techniques in each area. 

Corrosion processes can be very complex and, as the above examples show, surface analytical techniques can often provide unique information important for the understanding of these processes and to the solution of corrosion problems. By their basic nature, surface sensitive methods excel at examining thin layers at surfaces and interfaces that are difficult to detect and analyze by other methods but which can have a large influence in corrosion. The higher spatial resolution surface techniques are particularly useful for analysis of small area corrosion problems such as pitting and corrosion of electronic components and integrated circuits. 

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