Corrosion-resistant Foamed Cements for Carbon Steels Page: 3 of 28
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The cementitious material consisting of Secar #80, Class F fly ash, and sodium silicate designed
as an alternative thermal-shock resistant cement for the Enhanced Geothermal System (EGS)
wells was treated with cocamidopropyl dimethylamine oxide-based compound as foaming agent
(FA) to prepare numerous air bubble-dispersed low density cement slurries of 1.3 g/cm3. Then,
the foamed slurry was modified with acrylic emulsion (AE) as corrosion inhibitor. We detailed
the positive effects of the acrylic polymer (AP) in this emulsion on the five different properties
of the foamed cement: 1) The hydrothermal stability of the AP in 200 C-autoclaved cements; 2)
the hydrolysis-hydration reactions of the slurry at 85 C; 3) the composition of crystalline phases
assembled and the microstructure developed in autoclaved cements; 4) the mechanical behaviors
of the autoclaved cements; and, 5) the corrosion mitigation of carbon steel (CS) by the polymer.
For the first property, the hydrothermal-catalyzed acid-base interactions between the AP and
cement resulted in Ca-or Na-complexed carboxylate derivatives, which led to the improvement
of thermal stability of the AP. This interaction also stimulated the cement hydration reactions,
enhancing the total heat evolved during cement's curing. Addition of AP did not alter any of the
crystalline phase compositions responsible for the strength of the cement. Furthermore, the AP-
modified cement developed the porous microstructure with numerous defect-free cavities of
disconnected voids. These effects together contributed to the improvement of compressive-
strength and -toughness of the cured cement. AP modification of the cement also offered an
improved protection of CS against brine-caused corrosion. There were three major factors
governing the corrosion protection: 1) Reducing the extents of infiltration and transportation of
corrosive electrolytes through the cement layer deposited on the underlying CS surfaces; 2)
inhibiting the cathodic reactions at the corrosion site of CS; 3) extending the coverage of cement
over CS surfaces; and, 4) improving the adherence of the cement to CS surfaces. Thus, the CS's
corrosion rate of 176 milli inch/per year (mpy) for 1 wt% FA-foamed cement without AP was
considerably reduced to 69 mpy by adding only 2 wt% AP. Addition of AP at 10 wt% further
reduced this rate to < 10 mpy.
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T., Sugama; Gill, S.; Pyatina, T., Muraca, A.; Keese, R.; Khan, A. & Bour, D. Corrosion-resistant Foamed Cements for Carbon Steels, report, December 1, 2012; United States. (digital.library.unt.edu/ark:/67531/metadc844148/m1/3/: accessed December 13, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.