A technique used to control corrosion by making the metal surface the cathode of an electrochemical cell is called?

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Cathodic protection is the technique. By making the metal surface the cathode, the metal is kept from dissolving as it would when it acts as an anode in a corrosive environment. This is done either by connecting the structure to a more electronegative metal (sacrificial anodes) that corrodes in place of the protected metal, or by supplying an external current so electrons are delivered to the protected surface. The result is a significant reduction in corrosion since the oxidation reaction at the metal surface is suppressed. Anodic protection would purposefully push the surface to become an anode, which increases corrosion; passivation relies on forming a protective oxide layer without creating a galvanic cell; and while galvanic protection uses sacrificial anodes, the method is specifically about keeping the metal as the cathode.