An overview of the causes of decay and corrosion of reinforced concrete. The function of protective coatings in relation to the environment and the position of the concrete is explored. Concrete is defined and micro and macro effects reviewed as are surface and bulk effects. Reactive priming and substrate surface effects are detailed for an ideal system. Coatings are listed and parameters relative to protection are viewed in the context of experimentation. Conclusions are drawn having shown the need for more than just a protective function.