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Fatigue has already been mentioned as a longer term problem. The other major long term issue to be considered is corrosion. The device may have to operate in a chemical environment or even simply exposed to the weather or to full sunlight, which precludes the use of certain materials of requires coatings or other protection to separate the structure from that environment or sometimes the environment from the structure. (Stainless steel may be used for tanks containing corrosive fluids to protect the structure, but the same material may be considered for a surgical implant to protect the patient.) These are special cases, but even normal atmospheric moisture can cause corrosion, particularly when materials with dissimilar electrolytic properties are present. A simple electrolytic cell is easily created which will cause one of the materials to become degraded. Particular care is needed in the design of marine or coastal structures, or near roads in winter, where these effects may be exacerbated by the presence of salt. Care with detail design to avoid dirt and water traps, specification of appropriate paints and coatings, and, if necessary, the provision of insulating barriers to eliminate circuits can all help to avoid corrosion problems. It may be necessary to require structural inspection and routine repainting as part of a maintenance procedure.