Prediction of scaling in geothermal systems is important in order to be able to take preventive action. Scaling and corrosion processes are correlated in geothermal systems so that the factors influencing both processes are discussed in this paper. Pilot-scale equipment to model dissolution and scaling, and investigate corrosion, has been constructed. The construction of the pilot-scale equipment and the design of the experiments were based on the results of earlier laboratory model experiments. In order to check the measurement results we used a computer programe that was developed earlier, and which is suitable for the calculation of the equilibrium solubilities. Based on the results of the equilibrium experiments, we developed a modelling method for scaling in the pilot-scale equipment, and studied corrosion during scaling on the surfaces of five different structural materials. (C) 2000 CNR.