The adhesion of steel cord to rubber is very important for the quality of reinforced rubber products, e.g. tyres. Therefore, steel cord is often plated with brass, which will lead to CuxS bonds after reaction with sulfur compounds in the rubber. A unique in-situ analytical method has been developed to investigate the sulfur–brass interface: the sulfuring process has been simulated via a heating process in a water-free transparent ionic liquid with added sulfur and the reaction at the brass-coated steel cord has been monitored in real time with Raman spectroscopy. The grown CuxS film seems to be similar to the layers at the steel cord interface in real rubber materials. The model system can also be used to perform electrochemical measurements at the same time. The thickness of the CuxS layer has been estimated from the measured current during a cathodic stripping process. Copyright © 2013 John Wiley & Sons, Ltd.