Page 20 - Oil and Gas Simulations

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CORROSION
“You can use
COMSOL Multiphysics
with the Corrosion
Module to solve this
problem. All the work
that previously seemed
so difficult, now is so
easy because you have
the module doing a lot
of the work for you”
–SIDDIQ QIDWAI, MECHANICAL
ENGINEER, NRL
The properties of 316 steel were custom-
defined in the model. Simulation results
FIGURE 2. Corrosion in metals, such as stainless steel, is the result of electrochemical in the COMSOL environment, presented
reactions and mass transport in an electrolyte solution. An irregular corrosion front in Figure 4, demonstrate localized loss of
develops due to the material microstructure. material due to pitting.
In developing their multiphysics model
of pitting corrosion, Qidwai found that
the crystal orientation to calculate the “COMSOL is so versatile that it will give
“In developing a complex model, our corresponding pitting potential, which in you a solution even for very complex
strategy is to start with simpler numerical turn determines the corrosion rate and applications. This is where experimental
studies. Currently in our simulations movement of the front,” says Qidwai. validation is the key.” Insight gained from
we solve the electrochemical and mass The pitting potential is determined in their simulations has already provided
transport equations separately. In future MATLAB® for a particular crystallographic the impetus for the development of a
work, we will create a fully-coupled orientation and ultimately used by the novel experimental method to evaluate
electrochemical mass transport model of COMSOL model to calculate the corrosion corrosion at the micron scale. The results
corrosion.” To create their models, they rate and advance the corrosion front. from the experiments will be used to
have used the transport of diluted species “LiveLink™ for MATLAB® has been an validate the model and establish the
physics for mass transport, the Laplace essential feature for us in order to include relationship between microstructure, pit
and Poisson’s equations for the electric shape, and growth.
potential, and the moving mesh (ALE) the effect of the metal microstructure.”
technology for the corrosion front. “You
can use COMSOL Multiphysics with the
Corrosion Module to solve this problem,”
says Qidwai. “All the work that previously
seemed so difficult, now is so easy because
you have the module doing a lot of the
work for you.”
Incorporating the microstructure into
a multiphysics model of pitting corrosion
is a formidable challenge tackled initially
at NRL through the use of orientation
imaging microscopy (OIM) to acquire 3D
images of the metal microstructure. An
OIM-based reconstructed image of steel is
shown in Figure 3.
An integrated method was used to
incorporate the microstructure of 316
steel into a multiphysics model of pitting FIGURE 3. At right, the model geometry implemented in COMSOL Multiphysics to
corrosion implemented in the COMSOL® evaluate pit growth in metals. The reconstructed metal microstructure, at left, was
environment. “At every location along the determined using orientation imaging microscopy at NRL. The colored legend corresponds
corrosion front,
we have to determine to the crystallographic orientation of each grain.
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