RECENT ADVANCES IN CATHODIC PROTECTION

Cathodic protection is an electrical technique for preventing the rusting of iron and steel, a phenomenon which is usually considered a chemical reaction. Because of this the subject advances hand in hand with developments in electrical engineering and in the electrochemical industry and is modified in conjunction with advances in the chemical techniques for preventing corrosion. Magnesium, aluminium and zinc can be used as sacrificial anodes to provide cathodic protection and the greatest advance in this field has been the discovery of a new series of aluminium alloys which in sea‐water become cheap and effective sacrificial anodes. Impressed current techniques require a permanent anode and the plating of a very thin film of platinum on to a titanium substrate has been found to make an ideal anode. Much of the exploitation of this anode has taken place with new electrical techniques such as automatic control, the individual adjustment of anode current and a considerable improvement in the instrumentation. The extended experience of cathodic protection has given the contracting industry a very much greater knowledge of the design problems, of the spread of protection, of the degree of control and of the economic balance between the various techniques. A wider use of cathodic protection to supplement organic coatings and the development of coatings which work more readily with cathodic protection are two of the exceptional economic advances. Cathodic protection, unlike most anti‐corrosive treatments, is a continuous process, and as such it has to be maintained: the realisation of this has perhaps done more to produce the good results of which cathodic protection is capable, than any other single scientific discovery.