Chlorinated rubber coatings have proved to be effective anticorrosion materials for steel structures. However, their formulation and manufacture must be undertaken with extreme care - particularly as regards the chlorination process and the stabilizers and plasticizers added - in order to avoid early failures. This paper reports on the premature failure of a chlorinated rubber system that was applied directly over uncontaminated rusted steel. The accelerated formation of rust at the steel/paint interface rapidly resulted in complete degradation of the organic coating. Interfacial rust appears to catalyze the cleavage of the C-Cl covalent bonds in the polymer, which gives rise to the formation of chloride ions. These in turn have a dramatic accelerating effect on the corrosion of the base steel, thereby deteriorating the paint system. © 1993.

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