The effects of NaCl, a main component in seawater, on molten carbonate fuel cell (MCFC) performance is investigated using a single cell test with 1, 5, and 10 wt.% NaCl-impregnated cathodes for marine applications. The cell performance increases with increasing amounts of impregnated NaCl in the cathode. This cell performance enhancement is due to the reduction in the charge transfer resistance of the electrode. From the analysis of the electrolyte composition using the inductively coupled plasma (ICP) and ion chromatography (IC) methods after cell operation, it is confirmed that the Na+ ions are accumulated in the carbonate melts, and approximately 80 at.% of the Cl- ions are emitted into the anode outlet as HCl. Expecting that the emitted HCl causes severe corrosion of the utilities, the concentrations of accumulated Na+ ions of emitted HCl in the anode outlet are calculated when air with a sea-salt particle concentration of 5-500 ugm(-3) is supplied to the MCFC stack. Although HCl is a very corrosive gas, it is expected that the emitted HCl does not cause severe corrosion because, even at a high sea-salt concentration of 500 ugm(-3), the emitted HCl concentration is low enough to operate the stack safely. (C) 2013 Elsevier B.V. All rights reserved.