ACCELERATED DEGRADATION OF A CHLORINATED RUBBER PAINT SYSTEM APPLIED OVER RUSTED STEEL

Chlorinated rubber coatings have proved to be effective anticorrosion materials for steel structures. However, their formulation and manufac ture must be undertaken with extreme care - particularly as regards th e chlorination process and the stabilizers and plasticizers added - in order to avoid early failures. This paper reports on the premature fa ilure of a chlorinated rubber system that was applied directly over un contaminated rusted steel. The accelerated formation of rust at the st eel/paint interface rapidly resulted in complete degradation of the or ganic coating. Interfacial rust appears to catalyze the cleavage of th e C-Cl covalent bonds in the polymer, which gives rise to the formatio n of chloride ions. These in tum have a dramatic accelerating effect o n the corrosion of the base steel, thereby deteriorating the paint sys tem.