Previous laboratory studies reported in the literature and field experience have revealed the accelerating effect of the heavy metals lead and zinc on the corrosion behaviour of materials used in waste incineration plants. The major problem is that heavy metal containing chloride and sulphate salts usually have relatively low melting points, often below the metal temperature of the boiler surfaces. While the negative influence of lead and zinc is well-known, copper is another heavy metal that can occur in high amounts of up to 2000 mg/kg in refuse-derived fuel, which is the fuel produced by shredding and dehydrating solid municipal waste that is burned in modern waste-to-energy plants. The impact of copper additions on the corrosion behaviour of one iron-based austenitic alloy 1.4952 and three nickel-based alloys 2.4856 (alloy 625), 2.4633 (alloy 602 CA), 2.4605 (alloy 59), which are often used in waste incineration plants was investigated. The results of these studies clearly show the strong corrosive effect of copper content in salt mixtures on the corrosion of steels and nickel-based alloys.