Study of the Mass Transport on Corrosion of Low Carbon Steel Immersed in Sour Solution Under Turbulent Flow Conditions
Anticorrosión, Instituto de Ingeniería Universidad Veracruzana, Veracruz 2Instituto Mexicano del Petróleo, San Bartolo Atepehuacan 3Departamento de Ingeniería Metalúrgica, Facultad de Química Universidad Nacional Autónoma de México México 1. Introduction
A corrosion processcan be influenced, in different ways, by the relative movement between the metal and the corroding environment. This relative movement can increase the heat and mass transfer of reactants towards and from the surface of the corroding metal, with a consequent increase in the corrosion rate. Also, if solid particles are present, removal of protective films, erosion and wear on the metallic surfacecan occur. The corrosion of the metallic structure under turbulent flow is complex, but this problem has been studied mainly in the oil industry (Garnica-Rodriguez et al., 2009; Genesca et al., 2010; Mora-Mendoza et al., 2002; Papavinasam et al., 1993; Poulson, 1993), where, the flow and some gases are very important in the behaviour of the phenomenon processes. This oil industry has processesthat involve the movement of corrosive liquids in metallic structures, for example, the transport of mixtures of liquid hydrocarbons and gas with water through pipes. Therefore the influence of flow on the corrosion processes is an important issue to be considered in the design and operation of industrial equipment. This influence is complex and many variables are involved. Many observations offlowaccelerated corrosion problems have been documented (Dean, 1990; Garverick, 1994; Poulson, 1993). One aim that has been so much studied in the petroleum industry is the effect of flow and dissolved gases, such as hydrogen sulphide (H2S) and carbon dioxide (CO2). The most common type of flow conditions found in industrial processes is turbulent and according to increasing of the necessity todescribe the corrosion of metals in turbulent flow conditions some laboratory hydrodynamic systems have been used with different degrees of success (Poulson, 1983, 1993, 1994). Among these hydrodynamic systems, rotating cylinder electrodes (RCE), pipe segments, concentric pipe segments, submerged impinging jets and close-circuit loops have been used and have been important in the improvement of the
R.Galvan-Martinez1, R. Orozco-Cruz1, J. Mendoza-Flores2, A. Contreras2 and J. Genesca3
Hydrodynamics – Optimizing Methods and Tools
understanding of the corrosion process taking place in turbulent flow conditions (Liu et al., 1994; Lotz, 1990; Schmitt et al., 1991; Silverman, 1984, 1988, 1990). The use of the RCE, as a laboratory hydrodynamic test system, has been gainingpopularity in corrosion studies (Nesic et al., 1995, 2000). This popularity is due to its characteristics, such as, it operates mainly in turbulent flow conditions; it has a well understood mass transfer properties and it is relatively easy to construct and operate (Gabe, 1974; Schlichting & Gersten, 1979; Gabe & Walsh, 1983; Poulson, 1983). The critical Reynolds number, Re, for the transition fromlaminar to turbulent flow is 200 approximately, for a smooth surface laboratory RCE (Gabe, 1974; Gabe & Walsh, 1983; Poulson, 1983, 1993; Galvan-Martinez et al., 2010). This Reynolds value will be equivalent to a rotation rate 38 rpm, for a cylinder of 0.01 m of diameter immersed in a fluid of ν = 1.0E-06 m2s-1 (e.g. pure water). When the RCE is immersed in a fluid and rotated at a very lowrotation rate the fluid moves in concentric circles around the cylinder (laminar conditions). As the rotation rate of the cylinder increases the flow pattern is disrupted, cellular flow patterns, known as “Taylor vortices”, appear and the turbulent condition develops. These vortices enhance the mass, momentum and heat transfer at the rotating electrode (Gabe, 1974; Gabe & Walsh, 1983). In 1954, some...