A problem involving the localized corrosion of cast stainless steel in a Simplex Dispersator was referred to the writer. The Dispersator had been operated in a mixture of an organic liquid and water during the neutralization of an acid catalyst with caustic soda solutions and during subsequent water washing operations.
Figure 1 shows the Dispersator and a portion of the shaft. The unit consisted of a flanged hub casting, a body casting and an internal sheet metal vane. The back portion of the body casting had been cut away and the vane had been removed prior to photographing in order to show the perforations.
The shaft and the sheet metal vane conformed to AISI Type 304 stainless steel and the hub and the body castings conformed to ACI CFS as specified. Analytical results are given in Table 1.
Type 304 stainless steel specimens exposed in this environment exhibited corrosion...
