Dynamic pumps made of cast duplex stainless steel have demonstrated success for conveying sulphuric acid, chloride-containing suspensions in flue gas desulphurisation plants. After some years of problem-free operation at several installations, corrosion damage was observed. The reason for the corrosion of various parts was often attributed to operation in conditions below the specified pH-value. Additionally, fluorides in the suspension had an accelerating effect on the corrosion.

Specific experiments and investigations were carried out in order to develop a new cast duplex stainless steel with optimised chemical composition and specific heat treatment. A microstructure was achieved which enables the material to be used in extreme conditions.

Pumps made of this newly designed duplex stainless steel are now running for three years without any corrosion attack. Thereby excellent corrosion resistance has been demonstrated in practical service.