Archive | 2019
CORROSION RESISTANCE OF AISI 304 AND AISI 316 STAINLESS STEELS IN A SOLAR SALT USED IN CONCENTRATED SOLAR POWER PLANTS: THE EFFECT OF NaCl IMPURITIES
Abstract
High-temperature corrosion of stainless steels AISI 316 and AISI 304 in a molten «solar salt» used as a heat transfer fluid in concentrating solar power (60 wt.% NaNO3 and 40 wt.% KNO3) was investigated at the temperature of 550 C. It was shown that the corrosion rate is influenced by the composition of stainless steel and the presence of impurities NaCl in the solar salt. With an increase in the content of sodium chloride impurity in the solar salt, the corrosion rate of both stainless steels increases. The corrosion resistance to the destruction of stainless steels AISI 316 and AISI 304 is provided by the formation of (Cr,Fe)2O3 oxide film on the surface of the samples. Thus AISI 304 stainless steel with chromium content of ca. 20% shows higher corrosion resistance in the solar salt than AISI 316 stainless steel with lower chromium content (ca. 18%). It is known that AISI 304 stainless steel additionally contains molybdenum and a higher content of nickel. The presence of these transition metals in the composition of stainless steel also affects the formation of a protective oxide film that prevents further corrosion damage of steel samples.