A block copolymer as an effective additive for electrodepositing ultra-low Sn coatings

Abstract

In this work, a new type of block co-polymer additive, PE9400, was investigated for electrodepositing an ultra-low Sn coating in methanesulfonic acid (MSA) electrolyte. A thin coating with a loading of 0.7 g m⁻² tin was fabricated with excellent uniformity and coverage on wet temper rolling steel (WTRS), when PE9400 was used as an additive in the plating bath. Electrochemical measurements, real electroplating experiments, and SEM analysis, coupled with elemental qualification, indicated that the PE9400 additive results in a strong cathodic polarization with a wide operating current density range, resulting in fine grain size with even Sn distribution. These results confirm that PE9400 is able to significantly improve the quality of ultra-thin tin coating, giving rise to superior properties such as cloud point, surface activity, covering power and porosity compared to currently used Commercial TPG7 additive. Thus, this work may provide a new electrodeposition formulation to produce ultra-low Sn coating with sufficient quality for the Sn electroplating industry, which will significantly save tin sources for food packaging applications.