Scale iron oxide

Mill scale (rust) and pitting. The three layers of iron oxide scale formed on steel during rolling vary with the operation performed and the rolling temperature. When mill scale is placed in an electrolyte, any defect in the mill scale surface becomes the anode the remainder of the mill scale, which is usually many times larger than the defect, becomes a very strong cathode. An electric current can easily be produced between the steel and the mill scale. This electrochemical action will corrode the steel without affecting the mill scale. 

Figure 7.9 Micrograph of duplex iron sulphide-iron oxide scale formed on iron...

Iron oxide scale Oxidation of iron or low-alloy steels at temperatures >570 C (wustite stable) leads to a scale composed of an inner thick layer of wustite, Fei j,0, and two outer thinner layers of magnetite Fe3 04 and hematite Fe203. The disorder of Fei yO has been described in Sect. 6.2.2.1.3, its very high-iron vacancy concentration being the reason for fast outward cation diffusion and rapid growth. 

Iron oxides, scales CorrcKian under deposits ... 

Instrumentation malfunctions (distillation tower), 372-373 plugged orifice taps, 372-373 Insulated float chamber, 270 Insulation (energy savings), 218-219 Integral trusses (support lips), 84 Interface level, 303 Internal reflux, 13 Ionic hydrogen, 105 Iron oxide scale, 79 Iron sulfide, 372... 

The optimum pad thickness increases with operating pressure and 3-6, 10-20, and 35-45 gauzes are used in atmospheric, intermediate, and high pressure plants. Pads must be carefiilly fitted to avoid tears or creases and laid flat on a support of high-chrome steel mesh (Figure 4.5). New gauzes are free of lubricants and iron contamination, but old uzes can also be reused provided that they contain no holes and have been carefully cleaned and reactivated. Dust and other contamination is carefully removed and the gauze pickled in hydrochloric acid to remove iron oxide scale. 

As one of the early applications of the EBSD technique to the study of steel products, Randle found that the technique could be used to differentiate hematite, magnetite and wustite based on their respective pattern symmetry, Kikuchi band widths and pattern intensities, although no details of the phase recognition and analysis were provided [151]. In more recent years, Higginson and co-workers further explored the capabihty of EBSD in the analyses of iron oxide scale layers growing on low and ultra-low carbon steels, leading to a continuous stream of publications of their research results [153-162]. The technique was also used in the studies of other research groups [99,109,163-166],... 

B. Picque, P.-O. Bouchard, P. Montmitonnet and M. Picard, Mechanical behaviour of iron oxide scale experimental and numerical study . Wear 260,231-242 (2006). 

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