Effect of Sn on the Adhesion between Cu–Sn Alloy Coated Steel and Styrene Butadiene Based Rubber

Abstract

The effect of Cu–Sn coating on steel towards improving the adhesion between steel and typical styrene butadiene rubber (SBR) based tyre bead composition has been investigated in this work. Steel coupons were coated with varying compositions of Cu–Sn via immersion coating, where the electrolyte bath composition was varied. Chemical analysis of the coatings using ICP-OES confirmed increase in Sn content with increasing SnSO₄ concentration in the coating baths, keeping other parameters constant. No change in the surface roughness and coating weight was observed with change in Sn concentration in the coatings. The coated steel plates were vulcanized with SBR based rubber and peel strength was measured. The results confirmed an optimum Sn concentration of 3–4 wt% in the coatings up to which an increase (~ 25%) in adhesion strength was exhibited compared to only Cu coatings. Stereo-microscopic analysis of the peel tested samples validated mixed mode i.e. both adhesive and cohesive modes of failure.