Maintenance of protective systems on structures is an essential part of the overall strategy of protection (see Fig. 11.1) Maintenance costs enormous sums of money throughout the world, yet in many cases scant attention is paid to the overall problems of re-painting. Often an almost fatalistic attitude is adopted, yet, with the correct approach, considerable economies are possible. There are examples of structures where 30 coats of paint have been applied over the years; this can be checked by microscopic examination of detached paint flakes (see Fig. 11.2). Such areas generally have not corroded but, on the same structure, other parts have rusted quite badly because virtually no paint is present on the steel. It is possible that at the next repainting, a thirty-first or thirty-second coat will be applied to the sound areas and they will continue to protect the steel, while the corroded parts will, after wire-brushing and application of a three-coat system, be rusting again within a year or so.