Mechanistic insights into additives’ modulation of tin electrodeposition in sulfate electrolytes: synergistic effects and green – efficient production implications

Purpose This study aims to systematically investigate the effects and mechanisms of four additives – calcium lignosulfonate (CL), 2-naphthol, methanesulfonic acid (MSA) and gelatin – on the electrocrystallization behavior, nucleation mechanism and microstructure of tin deposits in sulfate electrolytes and to explore synergistic additive combinations for producing high-quality tin deposits. Design/methodology/approach Electrochemical behaviors and nucleation mechanisms were evaluated via cyclic voltammetry (CV), linear sweep voltammetry and chronoamperometry (CA). Single-additive influences on cathodic polarization, deposition potential and nucleation kinetics were systematically analyzed. A composite-additive system was optimized, and tin deposits were characterized by scanning electron microscopy (with annotated microstructural features) and X-ray diffraction (XRD) to evaluate surface morphology, phase composition and crystallographic preferred orientation. Current efficiency and specific energy consumption were quantitatively calculated with complete experimental procedures supplemented. Relevant published literature was referenced to compare and interpret the experimental observations. Findings Inhibitory additives including CL, 2-naphthol and gelatin adsorb onto electrode surfaces, inducing negative shifts in deposition potential and yielding refined-grain deposits, while MSA accelerates ion migration and nucleation rate. The optimized composite additive formulation consisting of gelatin, 2-naphthol and CL produces compact, smooth tin deposits with prominent (101)/(211) preferred orientation of tetragonal ß-Sn; no SnO2 impurity phases are detected from XRD patterns. Under the CA-3 composite-additive condition, the system achieves a current efficiency of 94.2% and specific energy consumption of 0.133 kWh·kg−1, showing improved electrodeposition performance compared with single-additive systems. Originality/value This work provides systematic mechanistic understanding of additive interactions in sulfate-based tin electrodeposition, clarifying the complementary roles of polymeric macromolecular inhibitors and aromatic leveling agents. The proposed synergistic additive formulation delivers feasible technical references for lab-scale preparation of high-quality tin deposits; further pilot-scale verification will be required for practical industrial deployment.