[en] For an economical energy conversion, liquid alkali metals will play an important role in heat transfer systems of fission and fusion reactors as well as in topping cycles. For the safe and reliable application of liquid metal technology, the knowledge of materials behaviour is essential. Using the results of corrosion tests on stainless steels in liquid sodium at temperatures around 1000⁰K and with a low oxygen content, a simple corrosion model is presented which, within certain limits, can be used to predict corrosion behaviour in K and Li systems. (Auth.)