Cathodic protection is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. This can either be done by using a sacrificial anode made from sink or similar material, or by applying an external direct current.
So… what has that to do with shaving? Well… normally it don’t, but J Duggan’s 1971 patent application on behalf of Warner Lambert Co combines the two.
The basic idea is rather simple, even if the patent text manages to make it sounds complicated:
In accordance with this invention, there is provided a corrosion protected razor and blade combination. The blade normally fabricated of corrosion-susceptible material is fixed in an appropriate holder providing an appropriate blade shaving position. A source of electrical energy of predetermined potential is then applied to the blade, which potential minimizes the corrosion susceptibility of the material.
There is also provided in accordance with this invention a method for protecting razor blades from corrosion. This method is provided by applying to the razor blade electrical energy of appropriate potential and polarity so as to render the blade substantially resistant to the corrosive action of its environment. In practicing this novel method, it has been found by empirical determination that the application of either positive or negative potentials to the blade edges of varying magnitude decreases the corrosion susceptibility of the blade material to a material extent.
So… two paragraphs of text to say that he invented a way to use cathodic protection to create a corrosion resistant razor-blade combination. Bear in mind that these two paragraphs comes after he spent most of a page outlining the history of battling the corrosion of razor blades… I think the guy writing was paid per word or something. On to the actual invention;
The source of electrical energy and the circuit for conducting such energy to the razor frame 5 and blade 11 are shown in outline form within the body of the handle 14. A battery 1 is connected with the appropriate potential through a substantially resistive element 2 by means of an electrical conductor which in turn is brought to the razor frame 5 by another conductor 3. The opposite output terminal of the battery 1 is then conveyed through another electrical conductor 4 to an electrode 8 mounted on a leaf spring member 6 associatively connected with the razor frame 5 to apply a bias force for fixedly holding the blade in its proper aligned position. A connective member 7 establishes conduction between the electrode 8 and the conductor 4. The conductor 4, conductor 3, resistor 2 and battery 1 are all potted or completely sealed within the plastic handle 14. Connections to the frame 5 and the connective member 7 are also made within the body of the handle 14, thereby providing maximum protection to the electrical connections which must be made and reliably maintained throughout the functional life of the device. Connections to the frame 5 and the connective member 7 may be made by welding or soldering or by merely a pressure connection, as for example crimping, if the desired crimping forces can be maintained and applied. Normally, the electrode 8 and the connecting member 7 are selected from the material having a higher cathodic potential or galvanic potential than the blade steel and the razor frame 5 and it is advisable that such be essentially a noble material such as platinum so that such electrode 8 does not enter into the chemical reaction of corrosion or corrosion protection which occurs when in an electrolyte environment.
Or in other words; a battery or other source of direct current in the handle, a resistor in series with the frame and blade, and an electrode insulated from the frame and blade. When water and/or lather comes between the blade and electrode, current will flow and the cathodic protection is active. When it dries, current will stop flowing, saving the battery. Capisce?
The rest of the patent is a decent read as well, with the initial essay on the history of anti-corrosion features of razor being of particular interest. It’s accessible on Google Patents.
As far as I’ve bothered to untangle things, Warner Lambert Co already owned Schick when the patent was issued, which most likely explains why the drawing primarily shows an injector style razor.