M.S.

An investigation of the factors affecting the corrosion rates of metals in hot tallol was undertaken to answer questions raised by previous investigators. The items studied were as follows: 1. The change in composition of tallol on heating was determined by heating tallol at 300° C. for 48 hours, and analyzing samples withdrawn at frequent time intervals. 2. The effect of change in composition of tallol was studied by determining the corrosion rate of steel in fresh tallol at 300° C., and in tallol which had been subjected to heating for 48 hours at 300° C. 3. The effect on the corrosive properties of the tallol of removing volatile components, of which a large proportion was water, was studied by determining the corrosion rates of aluminum, steel, nickel and copper at 300° C. when condensable volatile matter was returned to the system, and when it was allowed to escape. 4. The effect of water in the tallol was studied by determining the corrosion rate of steel in tallol at 300° C. for 48 hours, during which time water and other volatile products were allowed to escape, then adding water and repeating the corrosion test for five hours. From the results obtained in this investigation, it was decided that the most satisfactory correlation with plant data would probably be obtained by operating the test with fresh tallol at 300° C and replacing it every eighteen hours, allowing volatile components to escape from the vessel during the test periods. Separate tests must be made on those metals affected by ions of other metals, as shown by Keister(15) and Maguire(19). / M.S.