51313-02669-Understanding Corrosion and Its Inhibition in Chloride-Based Molten Salt Heat-Transfer Fluids

Available for download

Product Number: 51313-02669-SG

ISBN: 02669 2013 CP

Author: Sreya Dutta

Publication Date: 2013

Member Price: $0.00

Non Member Price: $20.00

Price: $20.00

Qty:

With increasing demands for renewable energy to meet electricity needs the need for alternative energy is growing rapidly. Concentrating Solar Power (CSP) provides an efficient way of converting solar energy to electricity and heat. Molten salts provide excellent high temperature media for thermal storage and heat transfer at temperatures above 500°C. High temperature and the corrosive nature of salt mixtures aggravate corrosion in these molten salt-based power plants. Using expensive high alloy materials for piping in the solar field requires an immense capital cost so it is beneficial to use less-expensive materials while still being able to circulate the fluid at high temperatures with minimal corrosion. Molten alkali nitrate (NaNO?- KNO?- based) salts cause extensive corrosion of stainless steel at temperatures above 500°C and with chlorides (combination of NaCl KCl ZnCl? LiCl AlCl? MgCl? and CaCl?) though the operating temperatures can be as high as 900°C the necessity for state-of-the-art alloys is paramount. An inhibitor package added to the molten salt can prevent corrosive attack on cheaper piping materials. Dynalene’s synthesis route comprises the addition of rare earth (La Y Gd) oxides alkaline earth (Mg Ca Ba etc.) oxides and alkali (K and Na) salts with amounts varying from 0.1-10 wt% to the chloride molten salt. Controlled heat-treatment of the melt with the additive will lead to the formation of a dense ceramic coating (such as perovskite) which would prevent leaching of the Cr ions. Introduction of the corrosion inhibitor package is effective in reducing the corrosion rate substantially for both the nitrate- as well as the chloride-based molten salts. Weight loss studies on the metal coupons introduced into the molten salts (with or without different additives) were performed to assess the corrosion rate. These coupons were characterized using SEM and EDS to study the extent and type of corrosion and also the composition of the inhibitive layer in presence of the additives. DC corrosion and electrochemical impedance studies will be conducted in high temperature electrochemical cells to understand the corrosion behavior of different metals in these molten salts.