Corrosion imaging

S. Livens, P. Scheunders, G. van de Wouwer, D. van Dyck, H. Smets, J. Winkel-mans and W. Bogaerts, A Texture Analysis Approach to Corrosion Image Classification, Microsc., Microanal., Microstrut t.. 7 (2) (1996), 143-152. 

In fig, 4 local corrosion by erosion is shown in a pipe with a bore of 100 mm behind a welding. In this case only the nominal wall thickness of the pipe is known (6.3 mm). To calibrate the obtained density changes into wall thickness changes a step wedge exposure with a nominal wall thickness of 13 mm (double wall penetration in the pipe exposure) and the same source / film system combination was used. From this a pcff = 1-30 1/cm can be expected which is used for the wall thickness estimation of the pipe image according to equation (4). 

Phenylenediamines are used in a variety of other appHcations, such as corrosion inhibitors, cross-linking agents for epoxy resins, toners for electrostatic image development (35), and to improve wrinkle resistance of cellulose acetate fibers (36). 

Fig. 9. Corrosion model of silver development. As the haUde ion, X, is removed into solution at the etch pit, the silver ion,, travels interstitiaHy, Ag/ to the site of the latent image where it is converted to silver metal by reaction with the color developer, Dev. Dev represents oxidized developer.

The desire to replace cadmium is generally attributed to its toxicity, both in terms of process pollution and product corrosion, and several alternatives are feasible thicker zinc, tin-zinc alloy or tin-nickel alloy depending upon the precise application " . The demise of decorative nickel-chrome systems in the automotive industries of the world is partly due to cost and partly to market image, and not to technical performance where major improvements took place in the period 1960-1975 through the establishment of duplex nickel under-layers and micro discontinuous chromium top-layers. In the 1980s the trend has been towards black finishes produced generally by powder-applied epoxy polymers. 

FIG. 36 Morphological changes of the sulfuric acid droplets as a function of time at about 94%. The three droplets (marked D) are the same as those shown in Fignre 35. After a period of time of abont 10 or more minntes, the droplets spread and coalesce (5). Spreading coincides with the corrosion reaction of the aluminnm snbstrate. Image size is 10 p,m X 10 p,m. (From Ref. 85.)... 

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