Abstracts Book - IMRC 2018

• SE4-O006
ELECTROCHEMICAL EVALUATION OF CARBON AND STAINLESS
STEEL AS STRUCTURAL MATERIALS FOR THERMAL ENERGY
STORAGE
Fabiola Pineda 1,2 , Magdalena Walczak 1 , Melissa Farias 1
1 Pontificia Universidad Catolica de Chile, Departamento de Ingenieria Mecanica y Metalurgica,
Chile. 2 Pontificia Universidad Catolica de Chile, Escuela de Construccion Civil, Chile.
Due to the implementation of solar-based energy technology, particularly by
concentrated solar plants (CSP), there is an increasing interest in corrosion of
structural materials, which are employed in thermal energy storage (TES). It should
be noted that the key component of TES is the heat transfer fluid (HTF), usually
molten salts, nevertheless they posing risk of corrosion to the materials in
contact. In this context, the present study aims at understanding the processes
involved in long–term exposition of carbon and stainless steel to molten salt at the
conditions specific to TES of CSP. The methods employed conventionally for
evaluation of corrosion in molten salts rely on the gravimetric and electrochemical
approached. Whereas, gravimetric measurements require long–term exposition,
the electrochemical alternative has not yet proved capable of providing equivalent
prediction of the expected rate of corrosion rate. Although understanding of
electrochemical testing has been well demonstrated on more common types of
corrosion, the experience with molten salts at high temperatures remains
incomplete due to experimental limitations and a valid challenge consists in
adapting electrochemical testing to better predict the onset of corrosion failure. In
this work, carbon steel grade ASTM A36 and stainless steel grade AISI 304 are
studied in exposure to nitrate salt mixture equivalent to so–called Solar Salt used in
TES of CSP, at temperatures specific to thermal energy storage. Electrochemical
technics are used to evaluate corrosion, in particular, electrochemical impedance
spectroscopy (EIS) is used to monitor the evolution and stability of the surface films.
Complementary techniques of surface characterization, FE-SEM and GD-OES are
employed for determine the chemical composition and thickness of the surface
films.
Acknowledgment: This work has been supported by CORFO Proyecto 13CEI2-
21803, Fondequip EQM 160091, Postdoctoral grant of School of Engineering of
Pontificia Universidad Católica de Chile.
Keywords: corrosion, molten salts, electrochemical impedance spectroscopy
Presenting authors email: fapinedap@uc.cl