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One challenge with concentrated solar power (CSP) systems is the potential corrosion of the alloys in the receivers and heat exchangers at high-temperature (700-1000 • C), which leads to a reduction of heat transfer efficiency and influences the systems durability. In this work, a corrosion model has been developed to predict the rates and mechanisms for corrosion of a nickel-based alloy that is in contact with a molten salt heat transfer system. In addition to accounting for heat and mass transfer effects on the corrosion, the model takes into account the electrochemical kinetics. Coupled with computational fluid dynamics (CFD), the local electrochemical environment and corrosion rates in a high-temperature molten salt system can be predicted. The kinetic, heat and mass transfer parameters used in the model are based on experimental studies conducted in a thermosiphon. The immersion cell was designed to expose coupons to the molten salt at isothermal or non-isothermal conditions between 700-1000 • C. The model can predict the effect of thermal gradients between the top and the bottom of the reactor which induce natural convection of the molten salt. The model has been validated against experimental results at different isothermal and non-isothermal conditions and good agreement has been achieved between the model predictions of the corrosion rates and corrosion potentials with the experimental observations.

Electrocatalysts for the bifunctional oxygen electrode for a PEM fuel cell/electrolyzer process need to be active and stable toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this work, Pt-Ir was synthesized supported on TiC and studied as a viable candidate to use as an oxygen electrode. Linear sweep voltammetry (LSV) and cyclic voltammetry (CV) were performed to measure electrochemical activity and compared with supported Pt and Ir on TiC, as well as commercial forms of unsupported Pt and Ir. It was determined that Pt-Ir on TiC outperformed the other electrocatalysts studied with a round trip efficiency of 65%.

One of the main focus areas of the 3013 Surveillance Program is a thorough evaluation of the inner container closure weld region (ICCWR) opened for destructive examination (DE). As part of the protocol to investigate the corrosion in the ICCWR a laser confocal microscope (LCM) is used to perform close visual examination of the surface and measurements of corrosion features on the surface. In FY17, DE containers from FY13 through FY16 were evaluated to select candidates for a full circumference analysis of the ICCWR. In FY18, the selected DE containers for full circumference evaluation (FCE) were processed according to the ICCWR protocol and LCM data collection was completed for the full circumference only for FY15 DE07. In FY19 the remaining DE containers were completed.The ICCWR protocol was completed as follows: (1) the FCE containers were sectioned into quarters and the weld removed to access the ICCWR; (2) a series of images of the ICCWR full circumference were taken using a stereo microscope and assembled into panoramic views; (3) SEM/EDS analysis performed on selected sections showed what is most likely corrosion products on the surface and chlorides randomly dispersed; (4) the presence of chlorides was also confirmed with ion chromatography of citric acid washes, in which FY15 DE07 and FY16 DE05 showed a significant amount of chlorides with FY15 DE08 showing the less amount of chlorides; (5) dye penetrant examination was performed on the interior and exterior surfaces of all the sidewall sections but reveled no relevant indication of surface-breaking defects, (6) finally, as described above, the full circumference examination of the ICCWR by LCM was completed.The three ICCWRs show general and localized corrosion on the surface. However, FY15 DE08 show more areas with agglomerated pits in Zones 2 and 3 than the other two DEs. The major suspect corrosion events were observed for FY15 DE07 on Sections C1 and C2 and for FY15 DE08 on Section C2. These events correspond to suspect cracks or crack-like features identified with a unique name to easily refer to each feature. FY15 DE07 shows a crack-like feature, identified as Acrux, in Section C1 and three features 07/25/2019

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