Intuition, case work and testing: A holistic approach to the corrosion of a 12% chromium steel in aqueous environments

3CR12 is a 12% chromium, corrosion-resistant steel designed to fill the gap between expensive stainless steels and cheaper carbon steels. It has found application in areas where corrosion/abrasion and aqueous corrosion problems arise. Widespread use of 3CR12 in these environments, since its introduction in 1979, has resulted in a large quantity of data on its performance. Many of the early recommendations for use in non-critical applications were based upon intuition and case by case experimental testing. With time this spawned a number of generic corrosion testing programmes. This resulted in the production of interesting, but often difficult to interpret, results concerning the performance of 3CR12. As market pressure for case history data grew a programme was developed to fulfil this need. This paper highlights the process followed from the release of 3CR12 into the market place to the production of predictive, usable data on its performance in aqueous environments. The disadvantages of environment-specific testing on a utility product such as this are highlighted and the growth in general, but difficult to interpret, data outlined. Techniques such as pitting scans, ZRA studies and experimental E-pH diagrams were employed to produce a number of predictive models. The integration and accuracy of these models was then tested against known case histories and this matched the ‘experience’ and ‘feel’ of various materials consultants. Bringing all these facets together has enabled a decison-based guide to be produced which takes the potential user step by step through the thought processes and information required for a selection decision. Clearly, a number of generalisations have to be made in such an approach but it is argued that provided these are highlighted, and examples given of how to overcome them, their use is justified by the advantages of having an easy to read material selection guide. A summary of the guide itself is given and comments on how it will be improved, as more information is gathered, discussed. The structure of the guide is such that important criteria such as temperature, pH, ionic species concentrations, Langelier Index, suspended solids and others are discussed in conjunction with design considerations to give a holistic approach to material selection. It is argued that technology and information transfer need to be improved to enable material users and specifiers to recommend appropriate materials, not just 3CR12, for various app