Corrosion of Aluminum-based Containers for Neutron Studies with Aqueous Samples under Low Temperatures

Abstract

Quasielastic neutron scattering studies frequently employ aluminum (Al) or Al alloys as sample cells. Due to the increasing incident-neutron flux, this research area has experienced continuous expansion; thus, the rate of acquiring data for dilute conditions has increased considerably. One such research topic is water-containing systems. In this study, we investigated the effect of temperature on Al and found that Al corrosion occurs even in a low temperature atmosphere. This was attributed to the different thermal expansion coefficients of Al as a base substrate and Al oxide as a passivating film.

Data Collection for Dilute Protein Solutions via a Neutron Backscattering Spectrometer

“…Figure 1 a shows S ( Q , E ) of the D 2 O-Boehmite coated Al cell at −0.01 < Δ E meV < 0.02, plotted on average at 0.13 < Q Å −1 < 1.7 after subtracting the background profile of the instrument and correcting for detector efficiency using a vanadium standard, and the profiles of an H 2 O-Boehmite coated cell and an untreated cell were also appended to the graph as references. Owing to the fact that the boiling times for the boehmite treatment with H 2 O [ 27 , 28 ] and D 2 O are 1 h and 15 h, respectively, the thickness of the formed boehmite film based on the literature values can be estimated to be roughly 0.5 µm and 6.5 µm [ 29 ].…”

“…Considering the incoherent cross-section of hydrogen and deuterium (H: 82.02 barn, D: 2.05 barn) and the estimated thickness of the D 2 O-Boehmite, this result is reasonable; furthermore, it was found that the H contamination in the D 2 O-Boehmite was small. The boehmite coatings can be expected to provide corrosion resistance even in the case of thin films [ 28 , 29 ]. However, in QENS experiments that require measurements over long periods of time, especially under high temperatures, the boehmite may form using water in the aqueous solution samples.…”

“…Such high-temperature experiments should be conducted using cells with a sufficiently thick layer of boehmite, obtained by boiling for 15 h or more. While the scattering intensity of the D 2 O-Boehmite-coated cell is higher than that of the untreated aluminum cell, the chemical reaction between water and aluminum under high temperatures can be suppressed [ 28 , 29 ], and the Q -dependence is small for Q > 0.3 ( Figure 1 b), making it useful as an empty cell for aqueous solution samples over a wide temperature range.…”

“…It should be noted that these changes could affect the stability of the sample, thereby deteriorating the quality of the resulting scattering profile. To overcome this problem, we adopted a boehmite coating of aluminum cells, which is expected to be corrosion-resistant over a wide temperature range [ 27 , 28 ]. To further suppress cell-derived incoherent scattering, a boehmite coating with deuterium oxide (D 2 O) was used in this study.…”