Effect of tinplated scraps surface-to-volume ratio on the efficiency of the electrolytic detinning process

Abstract

Recycling of steel scrap is a more competitive practice than steelmaking from iron ores. However, the presence of tramp elements within steel scrap affects the quality of the new steel produced. Tinplating of cans for drinks and food contains a high quantity of tin, which is responsible for adverse phenomena such as surface hot shortness and temper embrittlement. Thus, the development and application of a detinning process is necessary. This investigation focuses on studying an electrolytic detinning process performed in a 2.5M NaOH solution to decrease the tin content in tin-plated scrap. The process's performance was evaluated by varying input variables such as the process time, the applied current density, the operating temperature, and the material size (surface to volume ratio, S/V). The best process time for electrolytic de-tinning was estimated. The effect of the applied current density and S/V ratio on the process time and on the energy consumed by the process was evaluated at both room temperature and at 70 °C. The results showed that the tin content in tinned plates can be reduced to a negligible level (<0.01 wt-%) at 70 °C and the efficiency of de-tinning tin-plated scrap proved to increase with the S/V ratio.