The standards of the DIN 81249 series contain terms and their definitions, basic information, information and guiding values for the corrosion behaviour of unprotected, frequently used, metallic materials in contact with sea water or sea atmosphere. The special features of the material behaviour of various unprotected metals in metal-conducting contact with each other are described. The indicated numerical values are values from ranges of variations which have been formed as the mean from the values from numerous publications with very different boundary conditions. The information and numbers provide an indication of the corrosion behaviour of a metal which can be expected on average. Part 1 defines terms and definitions and specifies basic information.