The dissertation deals with heat treatment and coating technologies to increase the corrosion resistance of un- and low alloyed steel grades. The work is split into three chapters. The techniques gasnitriding and plasmanitriding were examined in terms of corrosion resistance. The influence of non-metallic inclusions has been determined onto the corrosion properties as well as the influence of the process control and the surface condition of the substrates. Both heat treatment technologies show different corrosion behavior while both nitriding technologies results in equal nitriding properties like white layer thickness or chemical composition. The pores in the surface of a gasnitrided sample have a major influence on the corrosion properties differently to plasmanitrided samples, these samples are corroding due to scratches or grinding grooves on the surface. Part two of the work investigated the post oxidation process of nitrided samples. The influence of different oxide layer thicknesses has been in the focus of the analysis. An increase of the layer thickness above 1µm shows a decrease of the corrosion properties. During oxidation of these ε-nitride layer nitrogen is set free and lead to pores and caves in the oxide layer. With an FIB analysis of the oxide layer and an in-situ measurement during oxidation with an mass spectrometer could be demonstrated that nitrogen is set free during oxidation. Part three of the work highlights the potential of thick diamond like carbon coatings for increasing the corrosion resistance of these steel grades. With special process control an coating layer thickness of 20µm and more were possible to generate. These layer lead to a corrosion resistant surface of the substrate.