Conductive cathodic protection compositions and methods

Abstract

Disclosed are improved compositions useful in providing a conductive layer or coating on or within a substrate. The compositions contain elemental carbon and a polymeric matrix or binder. The improvement comprises employing a unique ground calcined, coal-based coke which approaches graphite in terms of its performance as a conductive additive or pigment but does not possess the disadvantages associated with the use of graphite. The unique coke employed in the compositions and methods of the present invention has a significant level of graphitic structure. This level of graphitization can be most easily recognized by utilizing x-ray powder diffraction. More specifically, when the value of E.sub.c, or the inverse peak width (of the 002 peak), is measured for this material using Mo K.alpha. radiation (.lambda.=0.71 .ANG.), the value is in the range of about 27 to about 80, and preferably about 28 to about 75. The final compositions employ a polymer resin or matrix system as a binder which, when allowed to dry or cure, in situ, is water-permeable. They are useful as cathodic protection coatings for concrete and other building materials which are reinforced with low carbon steels and the like. The invention also relates to the method of applying the compositions to the reinforced substrate, and the resulting coated articles.