Comparative Laboratory Tests of Methanesulfonate and Sulfamic Tinplate Tinning Electrolytes

Resumo

Comparative tests are performed under laboratory conditions in units modeling existing electrolytic tinning units for contemporary ecologically clean tinning electrolytes based on methanesulfonate (Niveostan 200 version) and sulfamic acids. The main comparison criteria are: adaptability (the range of tolerance for the main parameters); hydrolysis stability and the level of sludge formation; tinned coating qualitative properties. It is shown that both types of electrolytes meet the specifications laid down for tinplate industrial tinning electrolytes and make it possible to prepare high quality anticorrosion coatings over a wide temperature range from 30 to 60°C, and they may provide good electrolytic efficiency (tin current efficiency 95%) with sensible limitation of the current density limit. Sulfamic electrolyte provides a broader range of variation in current density. Methanesulfonate electrolyte without admixture of iron is hardly prone to sludge formation. With an identical iron content (10 g/liter), both electrolytes have about the same low level of tin loss in sludge, but the anticipated rate of iron accumulation is greater in methanesulfonate electrolyte. The main advantage of methanesulfonate tinning is the high electrolyte electrical conductivity making it possible to reduce electrical energy consumption. Maximum use of the technical possibilities of both types of electrolyte is possible in new tinning lines planned and constructed in accordance with features of the production processes used.