Accelerated degradation of a chlorinated rubber paint system applied over rusted steel

Abstract

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.