Effect of zinc additions to NaCl-Na 2 SO 4 molten salt mixture on hot corrosion of Nimocast 713

Abstract

Hot corrosion studies were conducted at 900°C in a simulated combustion gas atmosphere containing sulphur trioxide at a partial pressure of 750 Pa on a nickel-base super alloy (Nimocast 713) partially immersed in various ZnSO₄–10wt-%NaCl–Na₂SO₄ molten salt mixtures. Weight changes were measured thermogravimetrically with time and it was found that the overall effect of the zinc sulphate addition was to reduce the degree of hot corrosion. Quantitative scanning electron microscopy investigations revealed no evidence of zinc in the attacked zone. It is postulated that the zinc reduces the chlorine activity in the system by forming a volatile chloride, thereby reducing the corrosive effect of the gas phase/molten salt mixtures. MST/507

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