Treatment of metal-containing ores using sulphuric acid creates a corrosive environment and places high demands on the material used for construction of process equipment. Leaching (atmospheric or pressure) is considered the most aggressive stage, with higher acid concentrations and temperatures, as well as contamination (dissolved metal ions and chloride ions), compared to downstream processes. The combination of sulphuric acid, dissolved metal ions and chloride ions results in competing corrosion mechanisms and complicates the prediction of corrosion, making it difficult to select a suitable material. This paper contains results from laboratory corrosion tests performed on a variety of stainless steel grades at different temperatures. The tests have been performed in simulated leaching environments based on dilute sulphuric acid with addition of oxidative metal ions and different levels of chloride ions. The results have been compiled into a corrosion resistance diagram which seeks to provide a schematic guideline to the selection of specialty stainless steel grades for these environments. High alloyed austenitic stainless steel grades as well as high strength duplex grades are covered in the guideline.
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