Abstract
A novel approach to measure mineral scale growth has been developed which is not only quantitative but also surface sensitive. In this study, a glass flow cell was used in conjunction with Laser Raman Spectroscopy to record the in-situ growth of mixed barium and strontium sulphate scale on the surface of 316 stainless steel. Studies of both uninhibited and inhibited growth are reported as well as the influence of specific ions. All experiments have been performed at room temperature and pressure and at constant solution pH.
In order to quantify these measurements, Secondary Ion Mass Spectrometry (SIMS) has been used to etch the precipitated scale from the surface of the steel. As the scale is removed, an elemental analysis of the sputtered ions is performed, resulting in a depth profile, which is sensitive to the presence of scale mineral ions on the steel surface. The etches were then imaged using Scanning Electron Microscopy (SEM).
Our data suggests that there was a large surface influence upon inhibition efficiency when compared with previously presented results (e.g. Yuan, 2000). A much higher concentration of inhibitor was required to prevent scale build up, compared with values determined in bulk precipitation tests, indicating the formation of inhibitorsurface complexes.
Most previous studies are non-surface sensitive and have utilised aqueous precipitation experiments to evaluate scale inhibition efficiency (Graham et al., 1997). Previous surface sensitive methods have used Atomic Force Microscopy (AFM) to observe scale precipitation and to measure the effect that nhibitors have upon the nature of crystal growth; however, this technique is not rate sensitive and thus the kinetics of scale build up have not been previously obtained (Bosbach et al., 1998).
