Phosphonate Scale And Corrosion Inhibitor Molecular Structure And Performance

The scale and corrosion inhibition efficiency of HPAA, HEDP, PBTCA, ATMP and EDTMP in simulated circulating cooling water was investigated by means of static scale inhibition test and rotating corrosion inhibition test. The scale inhibition efficiency on calcite has the order of HEDP > PBTCA≈ATMP > EDTMP. Meanwhile, HPAA, HEDP, ATMP and EDTMP have similar corrosion inhibition ability, with PBTCA less (base on molar concentration).The structures of molecule or ions of these scale and corrosion inhibitors in acid, neutral and base environment were optimized by density functional theory(DFT) of quantum chemical calculation, at the level of B3LYP , 6-31G*, 6-31G**, 6-31+G and 6-31++G, using the software Gaussian03. Significant quantum parameters were calculated, such as molecular orbit energies, dipolements, atomic charges and Fukui indices. The results indicate that the inhibitors play the function of scale and corrosion inhibition in the form of ions. The existence of carboxyl and hydroxyl groups can effectively increase the nucleophilic Fukui indices of double bond oxygen atoms in phosphate groups.At last, the interactions between negative divalent ions of these inhibitors, and calcite crystal surfaces (104), (102), (202) and (113) and Fe crystal surface (100) were simulated by the software Material Studio. The simulations were performed at NVT ensemble and Compass force field, then binding energy, nonbond interaction energy and pair correlation function were obtained to discuss the mechanism of scale and corrosion inhibition. The corrosion and scale inhibitors ca??eadily adsorb on the calcite surfaces and Fe (100) surface. The adsorption processes mainly supplied by ionic bond, with a certain degree of coulomb and van der waals force, the binding energy on calcite surfaces has the sequence of (113) > (102) > (202) > (114) which is consistent with experimental results.