Using synchrotron radiation wide angle X-ray scattering (WAXS) to study the inhibiting effect of polyphosphonocarboxylic acid (PPCA) on CaCO₃ scale formation

The aim of this paper is to further the understanding of scale formation and inhibition by in-situ probing of crystal growth by synchrotron radiation Wide Angle X-Ray Scattering (WAXS) in the absence and presence of Polyphosphinocarboxylic acid (PPCA) scale inhibitor at elevated temperature and high pressure It has been shown that the nucleation and growth of various calcareous polymorphs and their individual crystal planes can be followed in real time and from this the following conclusions are reached The process of scale deposited on the surface can be divided into an unstable phase and a stable phase. The initial phase of crystallization of calcium carbonate is characterized by instability with individual planes from various vaterite and aragonite polymorphs emerging and subsequently disappearing under the hydrodynamic conditions. After the initial unstable phase, various calcium carbonate crystal planes adhere on the surface and then grow on the surface PPCA inhibits surface deposition. It suppresses calcite formation and results in vateritedominated scale This is the first time that crystallization of mineral scale and its inhibition have been followed in-situ and as such, information on the nucleation and growth processes is accessible. This technique offers an exciting prospect for the study of scaling. © 2006 by NACE International.