Methanesulfonate System Tin Plating Additives And Process Research

Traditional electroplating tin system has many disadvantages such as low current efficiency, weak stability, largely corrosion to the equipment, refractory plating bath and contaminated environment. The methanesulfonate tinplate bath is a new type to electrolyte, and it has many advantages such as environmentally friendly, contains no toxin, stability and good performance and so on. In this paper, solution performance, deposit structure and properties has been studied by electrochemical workstation, X-ray diffractometer(XRD), scanning electron microscope(SEM) and electron spectrometer(EDS) in stannous methanesulfonate plating bath.(1)Effects of additives on electrodeposited tin cathode polarization, electrodeposition process, overpotential, electrochemical impedance spectroscopy(EIS), surface microtopography, preferred orientation in methansulfonate electrolytes. The effects of two baths to the properties of electrolyte which including electrochemical properties, current efficiency,deposition rate, dispersion, covering and deposition composition, microstructure, preferred orientation has been studied by electrochemistry performance text, Hull cell test, weight method, EDS, SEM and XRD in different processing parameter. The results show that when the matt additive were added into electrolyte, the cathode polarization and deposition rate increase, throwing power decrease, deposition efficiency initially increase and then decrease with the increasing of current density(0.5～4A·dm-2). Increase in current density made the tin electro-crystallization varied from outward to lateral growth modes and crystallization orientation varied from {321} and {431} to {112} and {332} crystal faces. The current density range increased and cathode polarization decreased when higher temperature, increase Sn2+ concentration or stir. The current efficiency and throwing power were up to 90% and 83%, good adhesion deposit and weldability, pure tin deposits were obtained. The brightener additive are added into electrolyte, overpotential increase, tin whisker decrease, microtopography change was not-obvious and crystallization orientation varied from {112} and {332} to {112} crystal faces with the increasing of current density(0.5～4 A·dm-2). The current efficiency and throwing power were up to 98% and 85%, good adhesion deposit and weldability, smooth, fine-grained and pure bright tin deposits were obtained.(2)The influence of different kinds of stabilizer has been studied by air oxidation, peroxide hydrogen oxidation and high temperature. The results show that,0.2g。L(?) hydroquinone and 0.1 g·L-1 ascorbic acid has the best antioxidant capacity. Stability of plating bath, which consisted of Sn2+, Sn4+, MSA concentration and cathodic polarization, has been studied by electrochemistry performance text and titration. The pilot scale experiment results show that when the stabilizers were added into electrolyte, the Sn2+ and MSA concentration keep balance. Electroplating 32 days, the Sn4+ concentration keep on the 3g·L-1. The cathode polarization slowly decrease with the increasing of plating time.(3)The corrosion study methods, which consisted of Tafel and EIS, were carried out to investigate the corrosion resistance for tinplate using chemical, cathodic and anodic passivation methods. It is shown that, the passivation films formation speed with the increasing of temperature. The chemical passivation temperature and time were 45℃and 8s, deposition has good corrosion resistance(charge transfer resistance was 502.2Q·cm2). The cathodic passivation temperature and time were 45℃and 3s, deposition formed complete passivation films, the corrosion current density and charge transfer resistance were 0.0123A.cm-2 and 1755Ω·cm2. The anodic passivation temperature and time were 20℃and 3s, the corrosion current density and charge transfer resistance were 0.00497 A.cm-2 and 1005.1Ω·cm2, the passivation films formation poor with the increasing of time.