Surface welding of duplex stainless steel on lamellar grey cast iron was performed to produce thick (several millimetres) protective surface layers with a regulated gas metal arc welding process. As dominant parameters, the influence of the composition of the shielding gas (argon-helium mixture) as well as preheating temperature on the corrosion resistance were investigated. Both the addition of helium to shielding gas and preheating of the base material increase the heat input and reduce the cooling rates and result in higher dilution. This leads to reduced hardness in the heat affected zone and prevents cracking. However, the formation and portion of carbides in the surface layers increase. The influence of these parameters on the microstructure in the surface layers as well as in the heat affected zone and the influence on the corrosion behaviour in artificial seawater were investigated with immersion tests and potentiodynamic polarization measurements. The corrosion properties of the parent lamellar grey cast iron were greatly enhanced by the surface layers, but inferior to duplex stainless steel. With additional metallographic investigations the corrosion mechanisms were investigated. The corrosion mechanisms are extensively influenced by the phase distribution in the surface layers and by the formation of carbides.Keywords: Grey cast iron / surface welding / regulated gas metal arc welding process / microstructure / corrosion Corresponding author: B. Heider, Zentrum fü r Konstruktionswerkstoffe (MPA-IfW Darmstadt), TU Darmstadt,