Spectrophotometric study of the corrosion behaviour of chromium in molten alkali carbonates

The corrosion of chromium species in molten (Li/K)2CO3 and (Li/Na/K)2CO3 are investigated by spectrophotometry. A strong charge-transfer absorption band is observed in the ultraviolet region with λmax=372 nm, and the molar absorptivity of CrO42− in molten (Li/K)2CO3 is calculated. The corrosion rates are investigated by means of increasing the concentration of CrO42− in the melts. Under an air atmosphere, the corrosion rate is slower in molten (Li/K)2CO3 than in molten (Li/Na/K)2CO3 and Cr2O3 corrodes more easily in molten (Li/K)2CO3 than Cr. With an atmosphere of CO2=1 atm, there is no increase in the CrO42− concentration in the solution phase during a period of 5 h.