Corrosion Behavior of Steels and Nickel Alloys in Superheated Steam

Abstract

Abstract Small amounts of a number of alloying materials were added to Type 304 stainless steel in an effort to improve its corrosion resistance to superheated steam at 650 C (1202 F), 42 kg/cm2. Aluminum and siliconwere valuable additions, but the amount of aluminum required to reduce the corrosion rate significantly embrittled the alloy. Type 304 containing about 3w/oSi appeared to be a practical alloy. In a similar fashion, the addition of about 3w/oAl to Incoloy 800 greatly improved its resistance to static superheated steam. Films stripped from samples corroded in steam with various prior surface preparations were examined by electron microscopy and chemical analysis in an attempt to clarify the reasons for differing corrosion behavior. It was concluded that the rapid diffusion of chromium into the corrosion films formed on mechanically worked surfaces is the key factor in the improved corrosion resistance of these surfaces.