Cathodic Protection: Historical

The first application of cathodic protection (CP) can be traced back to 1824, when Sir Humphrey Davy, in a project financed by the British Navy, succeeded in protecting copper sheathing* against corrosion from seawater by the use of iron anodes. This limited use of CP on copper sheathing perdured and when wooden hulls were replaced by steel the fitting of zinc protector blocks on the sterns of naval vessels became traditional. These zinc slabs, although they offered some protection to steel hulls against local galvanic effects due to the presence of the bronze propellers, were generally not deemed to be effective.

This lack of efficiency was mainly due to the use of unsuitable zinc alloys and other factors such as insufficient appreciation of the technology of cathodic protection and the tendency to reduce the efficiency of the zinc material to zero by painting their surfaces. From that early beginning, CP has grown to have many uses in marine and underground structures, water storage tanks, gas pipelines, oil platform supports, and many other facilities exposed to corrosive environments. More recently, CP has been proved to be an effective method for protecting and reinforcing steel from chloride-induced corrosion.

The CP effectiveness at protecting steel in soils has been demonstrated in the early 1940s when CP was applied to an old natural-gas piping network that had been developing leaks at a rapidly increasing rate, enough so that abandonment was seriously considered. The observed reduction in the number of leaks immediately after the CP installation was impressive.

Modern specifications for the cathodic protection of active oceangoing ships were first described in 1950. Since that time progress has been rapid. Considerable advances in cathodic protection technology have been made, better sacrificial anode materials have been developed, and circuits for the use of controlled applied current systems, using inert anodes, have been perfected.

The first reinforced concrete-impressed current CP system was an experimental system installed on a bridge support beam in 1959. A more advanced system was subsequently installed on a bridge deck in 1972. The anode system used in both applications was based on a conventional-impressed current CP system for pipelines, but “spread out” over a bridge deck. CP has since then become one of the few techniques that can be applied to control corrosion on existing structures.

Source: Roberge, P.R., Corrosion Engineering: Principle and Practice, McGraw-Hill