Table. 1. Parameters used in the study

Introduction: Generally changes in the fluid velocity

and the concentration of aggressive species on the

metallic surface, are decisive parameters in the

corrosion rate determination. In this work, the corrosion

phenomenon is studied in terms of interactions at the

solid-liquid interface, using a 3D-model to cylindrical

specimens.

Results: Uniform velocity profile, low turbulence and

different concentration distribution were observed close

to the specimen surface.

Conclusions: The high oxygen concentration in the

solid-liquid interface leads to obtain high corrosion

rates. More corrosion products would be deposited at

the top end of the specimen, limiting the oxygen

diffusion at the surface.

Computational Methods: The PDE’s are solved for an

incompressible and Newtonian fluid under stationary

conditions, considering:

1) Navier-Stokes and the continuity equation:

2) Nernst-Planck and the electroneutrality equation:

3) Electrochemical kinetic:

𝜌 𝒖 ∙ 𝛻 𝒖 = 𝛻 ∙ −𝑝𝑰 + 𝜇 𝛻𝒖 + 𝛻𝒖 𝑻 + 𝐹

𝜌𝛻 ∙ 𝒖 = 0

𝛻 −D𝑗𝛻𝑐𝑗 − 𝑧𝑗u𝑚,𝑗𝐹𝑐𝑗𝛻𝑉 + 𝒖𝛻𝑐𝑗 + 𝑅𝑗 = 0

𝑧𝑗𝑐𝑗𝑗 = 0

Mixed potential theory: 𝑖𝑇 = 𝑖𝐹𝑒 + 𝑖𝑂2 + 𝑖𝐻2𝑂

𝐹𝑒 → 𝐹𝑒+2 + 2𝑒−:

𝑖𝐹𝑒 = 𝑖0,𝐹𝑒𝑒𝑥𝑝2.303(𝐸−𝑉−𝐸𝑒𝑞,𝐹𝑒)

𝑏𝐹𝑒

2𝐻2𝑂 + 2𝑒− → 𝐻2 + 2𝑂𝐻

−:

𝑖𝐻2𝑂 = 𝑖0,𝐻2𝑂𝑒𝑥𝑝2.303(𝐸−𝑉−𝐸𝑒𝑞,𝐻2𝑂)

𝑏𝐻2𝑂

𝑂2 + 2𝐻2𝑂 + 4𝑒− → 4𝑂𝐻−:

𝑖𝑂2 = 𝑖0,𝑂2𝑒𝑥𝑝2.303(𝐸−𝑉−𝐸𝑒𝑞,𝑂2)

𝑏𝑂2

𝑐𝑠,𝑂2𝑐𝑏,𝑂2

Figure 1. Model geometry of the corrosion cell. (1) Flow inlet, (2) flow outlet, (3) Carbon steel specimen

(1)

(2)

(3)

Figure 2. (A) Velocity profile (m/s), (B) pH profile at ū=0 m/s, and (C) pH profile at ū=0.32 m/s, at E=-0.85 mV/SHE

(A) (B) (C)

References:

1. Caceres et al., Electrochim. Acta, 54, 7435 (2009)

2. Katsounaros et al., Electrochem. Commun., 13, 643

(2011)

Variable Value Variable Value

Cb,O2, mol/m3 0.21 CNaCl, mol/m3 1000

Solution pH 6.7 deq, m 0.0045

ū (inlet port), m/s 0.32 Re (annular

section) 1446

Figure 3. Partial polarization curves from mixed potential theory (left), radial oxygen dissolved profile (right)

Figure 4. Oxygen and pH distribution in axial direction

Numerical Simulation of Carbon Steel Corrosion Exposed

to Flowing NaCl Solutions Through an Annular Duct A. Soliz1, K. Mayrhofer1, L. Caceres2

1. Department of Interface Chemistry & Surface Engineering, Max-Planck-Institut f¿r Eisenforschung, D¿sseldorf, Germany

2. Department of Chemical Engineering, University of Antofagasta, Antofagasta, Chile

Acknowledgement. A. Soliz would like to

acknowledge to the Max Planck Institute for providing

the collaboration. This work was funded by

CONICYT/Becas Chile-Pasantía/75140004

0

1

2

3

4

5

6

7

8

9

60 65 70 75 80 85 90 95 100 105 110 115 120 125 130

Oxy

gen

co

nce

ntr

atio

n (

pp

m)

Corrosion cell length (mm)

-550 mV/SHE

-200 mV/SHE

-100 mV/SHE

Axial position of the specimen

--- ūinlet = 0 m/s — ūinlet = 0.32 m/s

Excerpt from the Proceedings of the 2014 COMSOL Conference in Boston