Effects of materials surface preparation for use in spacecraft potable water storage tanks

Wallace, William T.; Wallace, Sarah L.; Loh, Leslie J.; Kuo, Chia-Yi; Hudson, Edgar K.; Marlar, Tyler J.; Gazda, Daniel B.

doi:10.1016/j.actaastro.2017.09.034

Cited by 1 publication

(1 citation statement)

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“…At the very end of the test, Ag is almost fully depleted in the case of passivated SS316L, while for electropolished SS316L Ag concentration is slightly below the threshold limit of 0.2 mg/L. Regarding titanium alloy, Wallace et al [6,7] also recorded a remarkable silver reduction in the bulk, since the residual silver ions concentration was only 0.025 mg/L after 1680 h of exposure period and initial silver fluoride concentration into water of 0.4 mg/L. The test coupons were inserted to the test setup at S/V ratio around 0.6 cm −1 , while prior to exposure, the test coupons were passivated for 24 h into water containing 100 mg/L silver ions.…”

Section: Experimental Kinetic Datamentioning

confidence: 99%

Longevity Aspects of Potable Water Disinfected by Ionic Silver: Kinetic Experiments and Modeling

Petala

Tsiridis

Darakas

et al. 2020

Water

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In the International Space Station (ISS), Russian and European cosmonauts drink water disinfected by dissolved silver. For this to be effective, the concentration of silver should remain above a certain threshold from the moment of its initial disposition in storage tanks on earth until its final consumption in ISS. Unfortunately, during water tanks transportation to ISS and during storage in ISS, silver concentration has been reported to decrease intensively beyond any reason. This work examines the effect of different materials used in ISS water storage and distribution systems on the reduction of silver concentration. An experimental campaign has been organized where passivated stainless steel (SS), passivated and electropolished SS and titanium alloy coupons (official ISS grades) are exposed to simulated ISS potable water at different silver concentrations, different surface to volume ratios, and at stagnant or flow conditions. The evolution of silver concentration remaining in the bulk water is recorded with respect to the exposure time. A reaction engineering model for the Ag loss to the coupons is developed. The model is fitted to the experimental data in order to derive the reaction rate expression and the corresponding parameters. For passivated SS and electropolished SS the silver deposition rate depends on the initial silver concentration in water but is rather unaffected by the progress of silver deposition on the surface. On the other hand, for Ti alloy, while silver deposition rate still depends on initial silver concentration, it decreases continuously as silver deposition on the surface advances, implying that Ti alloy surface becomes gradually saturated and so prevents further silver deposition. Such a model can be useful for material selection and design of water storage and distribution facilities for ISS.

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Section: Experimental Kinetic Datamentioning

confidence: 99%