Alloy 33 is a recently developed Cr-Fe-Ni alloy, which can be used very successfully in sulfuric acid production as a material of construction after a carefully conducted material selection. Corrosion testing and evaluation to select a material for that kind of service is one of the really challenging tasks of materials engineering. This paper deals with some aspects of the complex nature of sulfuric acid corrosion and suitable methods for corrosion testing. Results of laboratory and field corrosion tests and some case histories of applications within that industry will be covered. At temperatures above 120 C the material offers a better performance than Si-alloyed stainless steels.

Other advantages of the 33weight% chromium containing fully austenitic material are the weldability including thick walled structures and the excellent corrosion resistance against local corrosion in chloride containing cooling water.

In laboratory corrosion tests promising results were found at concentrations above 97.5 weight % sulfuric acid up to 250 C, which should be considered for high temperature heat recovery systems. Further investigations should be performed to verify the technical potential of the alloy for such applications.