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Calcium Carbonate Scale Formation and Inhibition in the Presence of Zinc Ions QIWEI WANG, FAEZ AL-DAWOOD, AND HAMAD ALSAIARI, Saudi Aramco, Dhahran, Saudi Arabia Te inhibition efficacy of scale inhibitors is affected by many factors. Tis article discusses the impact of zinc ions on the performance of calcium carbonate (CaCO3 ) scale inhibitors. For inhibitors based on penta- phosphonate and polymer, performance can be improved by Zn2+ 60 MATERIALS PERFORMANCE November 2012 , but, the performance of tri-phosphonate-based products can deteriorate in the presence of Zn2+ . during oil production and processing operations. It forms at various locations and on many functional parts due to changes in the water's chemical composi- tion, or physical conditions. The effects of scale can be dramatic and immediate, ZIVOQVO NZWU ZML]KML WXMZI\QWV MNÅKQMV- cies and increased maintenance costs to loss of production and even system shut- C down. Even small amounts of CaCO3 deposit can cause malfunction of critical equipment, such as safety control valves and electric submersible pumps. Although CaCO3 scale problems can be mitigated with different approaches, the use of threshold inhibitor treatment is often the most cost-effective option. The effectiveness of threshold scale in- hibitors is affected by many factors, such as scaling ion concentration, pH, total dissolved solids (TDS), temperature, and the presence of suspended solids. Even some minor components, such as heavy UM\IT[ KIV [QOVQÅKIV\Ta QVÆ]MVKM \PM performance of scale inhibitors. Dissolved zinc ions (Zn2+ in water naturally. Zn2+ ) often exist comes from the partial dissolution of zinc-containing minerals in formation rocks by aquifer and connate water over geological time. Such reactions can yield very high Zn2+ concentrations in oilfield brine under high-pressure and high-temperature (HPHT) conditions.1 The dissolution of zinc-containing minerals also occurs when seawater or freshwater is used as ÆWWLQVO _I\MZ \W MVPIVKM WQT XZWL]K- tion.2 Zn2+ can also be added intention- ally as part of a chemical treatment pro- gram. In cooling water treatment, Zn2+ an important component for creating a synergistic effect with other corrosion inhibitors to provide good protection to carbon steel.3 Recently, Zn2+ NACE International, Vol. 51, No. 11 is alcium carbonate (CaCO3 ) scale is one of the most common types of inorganic deposits occurring in industrial water systems and has also