Materials Performance

DEC 2014

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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54 DECEMBER 2014 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 53, NO. 12 CHEMICAL TREATMENT Effect of Polymers on CaCO 3 Crystal Morphology with and without Fe 2 O 3 Numerous researchers have studied the influence of polymeric and nonpolymeric additives on the formation of CaCO 3 poly morphs. Sarig and Kahana reported inhibi tion of crystal growth of calcite by polyglu t a m i c s f r o m s t r u c t u ra l m a t c h i n g o f polymeric anions and cations in calcite crystals. 8 Dallas, et al.found that sulfonated poly(styrene) and poly(styrenedivinyl ben zene) are suitable substrates for the growth of CaCO 3 . 9 Kitamo reported that organic materials, with which calcium is strongly chelated, favored the formation of Mg 2+ rich calcite in the presence of Mg 2+ . 10 The authors investigated a number of additives as CaCO 3 inhibitors. Several con centrations of each additive were tested in the presence and absence of rust particles, giving results with %I values ranging from 2% to >85%. The characterization of the precipitating solids was done by xray dif fraction (XRD, Siemens D5000 † ) and cross examination of the reflections were imple mented according to files from the Joint C o m m i t t e e o n P o w d e r D i f f r a c t i o n Standards ( JCPDS). It should be noted that in all experiments where additives were tested in the presence and absence of rust particles, only reflections corresponding to C a C O 3 p o l y m o r p h s w e r e o b t a i n e d . Photographs were taken by scanning elec t r o n m i c r o s c o py ( SE M ) ( L E O SU PR A 35VP † ) to assess the effect of polymers in the presence and absence of rust particles. Figure 6(a) illustrates the characteristic rhombohedral morphology of CaCO 3 (cal cite) in the absence of additives and Fe 2 O 3 . Aragonite is also present in the CaCO 3 . Figure 6(b) shows the effect of Fe 2 O 3 on CaCO 3 in the absence of an additive. Both calcite and aragonite are covered with nanoparticles of Fe 2 O 3 . Figure 6(c) presents a SEM micrograph of CaCO 3 formed in the presence of HP1. A dramatic change in the morphology of CaCO 3 precipitated in the presence of HP1 is evident. Provided that the precipitation was spontaneous, it is † Trade name. FIGURE 3 Effect of varying amounts of Fe 2 O 3 on the performance of HP1 (5 mg/L). FIGURE 4 Performance of HP1 in the presence of 0 and 50 mg of Fe 2 O 3 and varying dosages of HP1. were conducted in the presence of 2.5 mg/L of polymers and 50 mg of Fe 2 O 3 . The poly mers tested were HP1, HP2 (carboxymethyl inulin), HP6 [ p o ly(m al ei c a ci d)], C P1 [poly(acrylic acid: 2acrylamido2methyl propane sulfonic acid)], and terpolymers TP1 (acr ylic acid:SA:SS [sulfonated sty ren e)], and TP2 (acr y lic aci d:S A:sAM [sacrylamide]). Figure 5 shows the results obtained in the presence of 2.5 ppm of poly mers, and 50 and 0 mg of Fe 2 O 3 . Under simi lar experimental conditions, all polymers lost their inhibition ef ficacy to var ying degrees in the presence of Fe 2 O 3 . In general, loss in performance is ~50 to 70%. The decreased %I values obtained in the pres ence of Fe 2 O 3 ref lected the depletion of polymer concentration in CaCO 3 supersat urated solutions via adsorption onto Fe 2 O 3 particles.

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