An improved technique for molten salt corrosion sample preparation

Proper materialographic sample preparation is vital in electron microscopy to produce the best quality material results, nearest to its true structure. Environments and media such as molten salts render traditional methods inadequate for analysis. An evaluation of conventional preparation techniques with different lubricants on 316 L stainless steel from its interaction with 59.4/40.6 wt% Na2CO3/NaCl eutectic salt show how corrosion layer information is lost or retained. Additional large-scale composite electron imaging and compound analysis work on the corrosion effects of 68.05/31.95 wt% Na2SO4/NaCl was also investigated on C-276 nickel superalloy. The new adaptation of sample preparation using kerosene as a lubricant is the best available option for compound analysis of molten salt corrosion, allowing corrosion mechanisms to be more well understood. The method also provided a sample surface that allows phase mapping and compound identification to a higher degree of accuracy than previously seen in the literature. •Isothermal testing of 316 stainless steel in molten NaCl/Na2CO3.•The new preparation technique left the corrosion layers and salt intact.•A combination of kerosene and diamond paste polished the samples.•Electron microscope elemental maps are much more refined than shown in literature.•Information garnered from using this methodology furthers solar thermal research.