The historical development of marine cathodic protection design, along with the recently developed, fwst principles based slope parameter method, is briefly reviewed. From this, it is projected that remaining issues which require resolution before cathodic protection design can be optimized are improved methods for repmemting 1) the slope parameter, 2) anode current capacity, and 3) mean current density. The present paper focuses upon the last of these and, in so doing, evaluates data from a variety of field structures for which such information exists and from laboratory/field test programs. An analytical model for current density decay with time, in conjunction with calcareous deposit formation, is presented; and a new method is proposed for specifying mean current density in cathodic protection design of offshore structures. Keywords: cathodic protection, sea water, offshore structures, galvanic anode, slope
parameter, design, analytical model, mean current density.