Local reactions between NaCl and KCl particles and metal surfaces

Abstract

Local reactions of NaCl particles with pure iron surfaces have been investigated to compare with the results of previous studies on the local reactions of KCl particles. Before short-term oxidation at various temperatures in N₂–20 vol.-%O₂–0·05 vol.-%HCl atmospheres, microscale NaCl particles were deposited by thermophoresis on bare iron surfaces and pre-oxidised samples. After reaction, the samples were examined using field emission microscopy (FEM), X-ray photoelectron spectroscopy (XPS) and chemical analysis. In particular, NaCl particles reacted with the iron surface at 300°C, depending on the gas phase composition. In N₂–O₂ atmospheres very local reactions took place, whereas the addition of 500 vppm HCl led to complete coverage of the iron surface with chloride. In addition, the reactions of KCl particles on nickel surfaces at 500°C have been investigated for comparison with those of KCl and NaCl particles on iron surfaces at 300°C.