Abstract
316H samples were exposed to NaCl-MgCl2 in sealed static capsules at 600 and 700°C for 500h. Salts were purified prior to use, and water was added to half of the capsules to make the salt more aggressive. Metallic Mg was added to half of the capsules to asses its impact on corrosion of the 316H samples.
Samples exposed in capsules with added water were attacked more severely. Addition of metallic Mg was found to decrease corrosive attack in all conditions. After exposure, Cr and Fe were found in the salts, roughly proportional to the severity of corrosive attack. Near-surface areas showed that alloy constituents were attacked roughly uniformly, with little evidence of selective attack of the more active alloy constituents such as Cr.
Thermodynamic calculations are presented to illustrate potential explanations for these findings. This work shows that metallic Mg is a promising redox control additive in chloride salts. The effectiveness of Mg addition in salts both above and below the melting point of Mg suggest it may be effective in flowing systems that operate with a temperature gradient.
