X-ray photoelectron spectroscopy and Auger electron spectroscopy of the influence of cations and anions of organometallic adhesion promoters on the interface between steel cord and rubber skim compounds

The influence of cations and anions of the adhesion promoters on the interface between brass-coated steel cord and natural rubber skim compounds has been studied by employing Auger electron spectroscopy and X-ray photoelectron spectroscopy at three different etching times. Cobalt stearate, cobalt boroacylate and nickel boroacylate have been used as organometallic adhesion promoters. The atomic concentrations of sulfur and carbon decreased, while those of copper and zinc increased significantly with etching times. Cobalt/nickel was only found at higher etching times. Cobalt boroacylate increased the atomic concentration of copper, zinc and sulfur with the formation of CuxS and ZnS on the top two layers more than the nickel boroacylate. The sulfidation reaction was, however, only partial in the presence of cobalt stearate, and ZnO was observed in the top layer. The atomic concentrations of copper and zinc were also much lower than those of the system containing cobalt boroacylate. A model, based on the results, is proposed to show the difference in activity of the cations and anions.