Electrochemical scaling of stainless steel in artificial seawater: Role of experimental conditions on CaCO 3 and Mg(OH) 2 formation Héla Karoui a, b , Benoit Riffault a , Marc Jeannin c , Abdelkarim Kahoul d , Otavio Gil a , Mohamed Ben Amor b , Mohamed M. Tlili b, ⁎ a Equipe de Recherche en Physico-Chimie et Biotechnologies E.R.P.C.B. (EA3914) Campus II- Sciences 2- IUT de Caen—Université de Caen Basse-Normandie, Bd du Maréchal Juin 14032 CAEN, France b Laboratoire de Traitement des Eaux Naturelles, Centre des Recherches et Technologies des Eaux, Technopole Borj Cédria, BP 273 Soliman 8020, Tunisie c Laboratoire d'Etude des Matériaux en Milieux Agressifs (LEMMA) EA 3167, Université de la Rochelle, Av Michel Crépeau, 17042 La Rochelle, France d Laboratoire d'Energétique et d'Electrochimie du solide, Université F. Abbas de Sétif, 19000-Sétif, Algérie HIGHLIGHTS ► Unlike other substrates, stainless steel promotes Mg(OH) 2 electrochemical scale. ► The temperature favours the brucite formation on stainless steel. ► Scaling process starts by brucite formation; then, the aragonite occurs on it. abstract article info Article history: Received 7 March 2012 Received in revised form 5 July 2012 Accepted 7 July 2012 Available online 15 August 2012 Keywords: Stainless Steel Scaling Brucite Seawater Calcium carbonate In seawater, during the application of cathodic protection, a scale layer forms on the metal surface. As func- tion of its chemical composition and compactness, it can improve the metal protection against corrosion by reducing the oxygen diffusion. The present investigation focuses on the electrochemical scaling of stainless steel in artificial seawater. Formed scales were characterized by X-ray diffraction, Raman spectroscopy and scanning electron microscopy. It was found that the formed scales are mainly CaCO 3 aragonite. The brucite (Mg(OH) 2 ) was identified, as a component of the scale layer, only for a high temperature and a more cathodic potential. It was also shown that, unlike other substrates, stainless steel promotes the precipitation of brucite. If the experimental conditions favoured its formation, the scaling process starts with brucite deposition. The growth of CaCO 3 nucleuses, developed on interstice, recovers after brucite layer. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Stainless steels (SS) are one of the most tonnage alloy materials used for industrial and domestic purposes. Its corrosion resistance in a wide variety of aqueous environments determines its use in many applications. However, SS like other materials is a scaling prone. Mineral deposition can have a beneficial effect in terms of corrosion protection especially in the field of the cathodic protection, whereas, in industries where saline fluids are transported such as in water desalination systems, oil recovery and power generation it can generate major problems [1,2]. As function of the water use and chemical composition, different precipitates were iden- tified in heat exchange surfaces [3,4], cooling water systems [5] and oilfield production wells [5,6]: BaSO 4 , CaSO 4 and CaCO 3 ; each having dif- ferent thermodynamic tendencies and kinetics of formation, but scale is far dominated by calcium carbonate. In sea water, the high concentration of the magnesium ions plays an important role on scale formation for physico-chemical properties of the deposit and kinetics' point of view. For instance, some studies were devoted to investigate the magnesium ions' contribution on the nucleation-growth process of calcareous deposition [7–13]. It has been shown that Mg 2+ delays the CaCO 3 deposition and promotes the arago- nite shape instead of calcite and vaterite [12–20]. In addition, it was shown that magnesium ions favour the heterognenous precipitation of calcium carbonate [12]. Under cathodic protection conditions, when chemical and thermo- dynamical conditions are gathered, magnesium can lead in seawater to the precipitation of brucite Mg(OH) 2 [7]. Below we recall briefly the pos- sible chemical and electrochemical reactions which can evolve on the cathode for a potential range of -0.8 to -1.2 V/SCE (Saturated Calomel Electrode): it can create the reduction of oxygen which can be split into two elementary steps: O 2 þ 2e - þ 2H 2 O→2OH - þ H 2 O 2 ð1Þ Desalination 311 (2013) 234–240 ⁎ Corresponding author. Tel.: +216 79 32 50 44; fax: +216 79 32 58 02. E-mail address: mohamed.tlili@certe.rnrt.tn (M.M. Tlili). 0011-9164/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2012.07.011 Contents lists available at SciVerse ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal