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Fig. 5 | Geothermal Energy

Fig. 5

From: Scale-fragment formation impairing geothermal energy production: interacting H2S corrosion and CaCO3 crystal growth

Fig. 5

High spatial resolution electron microprobe back-scattered electron images and elemental maps (Ca, Mg, Fe, S, Si) from the basal sections of two different scale-fragment samples (a, b). The precipitated scale material consists of homogeneous Mg-calcite indicated by the measured Ca and Mg concentrations. The basal corrosion layer primarily consists of iron sulfide minerals (Fe and S concentrations) resulting from gradual alteration of the conventional steel (pink color indicating high elemental concentration on relative color range). Elevated silica contents (Si) are typically associated with the Fe-sulfide layers. Note the frequent occurrence of cracks displacing sulfide corrosion products and related scale carbonate (red arrow in BSE image)

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