Review of corrosion issues and material solutions in the CPI

The chemical process and petrochemical industries are large users of high grade corrosion resistant materials. These industries have to cope not only with very corrosive service environments but also with the technical and commercial challenges of rigid environmental regulations and a permanent strive to rise production efficiency by utilizing higher temperatures and pressures, and more corrosive catalysts. A large number of chemical processes can only be carried out safely and economically if nickel alloys and special stainless steels are used.

Over the past 50 years improvements in alloy metallurgy, melting technology, and thermo-mechanical processing, along with a better fundamental understanding of the role of various alloying elements have led to the development of new corrosion resistant alloys. These extended the range of usefulness beyond that of existing alloys by overcoming their limitations and also improved cost efficiency, reliability and opened new areas of application. Interestingly, there seems to be a synergistic interaction between the implementation of new processes for production of specific chemicals and the development and market introduction of new corrosion resistant alloys.  Especially the development of the high performance C-alloy family and the increase of the molybdenum content in steels to approx. 6% have answered important requirements of the chemical process industry and the availability of these new alloys made possible to successfully upscale various processes into an industrial scale.

It is the aim of this work to report about these challenges and achievements. The major nickel alloy systems are discussed, including their major characteristics and their contribution to solve corrosion problems in various applications of the chemical process industry. Special emphasis is given to the 6% Mo special stainless steel alloy 31 (UNS N08031) and the nickel-chromium-molybdenum alloy 59 (UNS N06059).