The potential of adsorption of scale inhibitor and indeed other cations such as magnesium and calcium, promoted by electrochemical pre-treatment, to effectively protect metallic surfaces from the adhesion and growth of calcium carbonate scale is investigated in this study. An experimental study has examined the effect of pre-treatment of rotating disk electrode (RDE) surfaces in preventing scale deposition. The beneficial effect of the divalent Mg 2+ cations, present during pre-treatment has been demonstrated. Visualization of the amount of scale deposition, with and without electrochemical pre- treatment, has been conducted using scanning electron microscopy (SEM).
In summary, this paper describes the beneficial effects of using an electrochemical pre-treatment to inhibit scale deposition on metal surfaces and assesses the cation/inhibitor interactions and their effect on inhibitor efficiency.
The nucleation and growth of scale (i.e. insoluble mineral salts) on metal surfaces of plant components such as valves and pipework is one of the main aspects of crystal formation, which causes operational problems in industrial facilities. In addition, formation of scale in the pores of rock can cause plugging of wells and scaling in rock pores has received widespread attention 1. Deposition on 1 production equipment (e.g. pipework) can lead to increased turbulence in flow systems and can eventually block flow lines.
Notwithstanding the extensive problems associated with scaling on component surfaces, the main effort in scale research has been to develop an understanding of scale formation (precipitation) in the bulk solution and several models have been developed to assess the scaling tendency of particular waters based on thermodynamic data 2. Well-management programmes often rely on information such as this to control scale formation and indicate inhibitor dosing rates. In terms of bulk scaling studies the methodology commonly adopted for assessing the efficiency of inhibitor chemicals is based on NACE standard TM01973 in which the scale-forming ion concentration is measured (by Inductively Coupled Plasma (ICP) for instance) when two brines are mixed and scaling occurs. The effectiveness of inhibition is evaluated by comparing the ion concentration in presence and in absence of inhibitor after bulk precipitation has occurred. This method has been used to rank the efficiency of inhibitors in a wide range of environments 4. One limitation of this is the fact that there is often little or no correlation between the bulk scaling tendency and the tendency for surface deposition as was realized by Hasson et al 5. Hence there is often a need to determine the kinetics of scaling at the solid surface.
