Erosion and cavitation are the life-determining wear mechanisms of water power machines. Provided that suitable surface protection measures are taken, the availability of the machines can be increased and their maintenance costs can be significantly reduced. This paper provides the evaluation of various criteria for the selection of suitable coating systems. It describes results determined experimentally and achieved in operational use in hydropower plants. The paper also provides an estimate of the achievable extension of the maintenance according to the protective measures. Paper includes a German-language abstract.