Anodic corrosion of Hastelloy-C in sulfuric acid solution

The corrosion behavior of anodically polarized Hastelloy-C was investigated in an 1N sulfuric acid solution by using various methods as follows; e.g. potentiostatic and potentiokinetic polarization characteristic measurements, colorimetric analyses of the dissolved alloy elements and ESCA method. Both of the two kinds of polarization characteristic measurements gave results indicating that the alloy behaved in three different ways according to the potential from -0.2 to 1.0 Volt vs S.C.E. Below 0.2 V, although iron tended to selectively dissolve, the total amount of dissolution was very slight and the alloy was almost maintained in a passive state. At the potential between 0.2 and 0.8 V, local attack of the alloy and selective dissolution of molybdenum were observed. The electrolytic current reached its maximum value at 0.6 V, and a steep rise of the current was observed at about 0.9 V. Above the latter potential, the alloy was uniformly attacked and all elements dissolved in proportional manner to their alloy contents. Different ESCA spectra were also obtained according to the polarization potential. (auth.)