A major challenge faced by the oil and gas industry is the minimization of scale formation within installations; new regulations are requiring conventional inhibitors to be replaced by green chemistries or green scale inhibition strategies which may involve anti-fouling surfaces. This paper focuses on the ability of different surfaces to reduce or modify calcium carbonate scale formation with the final objective being to understand what constitutes a surface that minimises the potential for scaling. Seven different surfaces have been tested (stainless steel, stainless steel pre-treated with Polyphosphinocarboxilic Acid (PPCA), Polytetrafluoroethylene (PTFE), Diamond-Like Carbon (DLC), ceramic and polymer coated stainless steels and an isotropic superfinished stainless steel surface). A subset of these surfaces was eroded within a Submerged Impinging Jet (SIJ) to assess the possible effect of in-service performance. The surfaces were first characterized by contact angle, roughness measurements and Energy Dispersive X-ray (EDX). Calcium carbonate growth, under flow conditions, has been assessed for each of the surfaces by studying the amount of scale and the morphology of the crystals using Scanning Electron Microscopy (SEM). From the results, a systematic ranking of the surface resistance to scaling has been established together with an improved description of the scale deposition process.

Millions of dollars are spent every year to prevent or remove scale occurring on oilfield components.1 These deposits cause severe technical problems which can lead to the loss of efficiency or in most cases necessitate the replacement of equipment.2 Understanding calcium carbonate formation on surfaces is a crucial step in improving inhibition methods. The entire scaling process can be divided into two parts; bulk precipitation and surface deposition. Both processes have been widely studied using a variety of methods. However, little is understood from a fundamental perspective regarding surface deposition. In this paper, attention is focused on the ability of different surfaces to reduce and/or to delay calcium carbonate formation. In flowing conditions the effect of different substrates (stainless steel, stainless steel pre-treated with Polyphosphinocarboxilic Acid (PPCA) scale inhibitor, Polytetrafluoroethylene (PTFE), Diamond-Like Carbon (DLC), ceramic and polymer coated stainless steels and an isotropic superfinished stainless steel surface) are tested. The surfaces have been characterized by Energy Dispersive X-ray (EDX), contact angle and roughness measurements before deposition. The quantity and morphology of crystals were assessed by Scanning Electron Microscopy (SEM), the image then being analysed with Matlab to obtain the surface coverage. In addition, the durability of the coatings was tested and their potential for scaling reassessed following erosion. It has been assumed for some time that hydrophobic surfaces have better performance regarding materials biofouling.3 However, the scaling process is a crystallization process and it is not obvious that hydrophobicity should be the key parameter in controlling this type of fouling.4 In this paper, the isotropic superfinished surface being the most hydrophilic among the surfaces tested showed the greatest potential to reduce calcium carbonate formation. A difference of the crystal morphology has also been observed for the PTFE, isotropic superfinished surfaces and eroded DLC.