cathodic

Cathodic refers to anything related to the cathode in electrochemical systems. The term is used to describe processes, surfaces, or protections associated with the electrode at which reduction occurs. In electrochemistry, the cathode is the electrode where electrons are consumed by species in the solution or on the surface.

In galvanic (voltaic) cells, the cathode is the positive electrode, while in electrolytic cells the cathode is the negative electrode. Regardless of the context, the cathodic region is where reduction reactions take place, with electrons flowing into the electrode from the external circuit.

Cathodic processes include the reduction of metal ions to deposit metals, the reduction of protons to hydrogen gas in aqueous solutions, and various other reductions depending on the solution chemistry. These reactions compete with anodic processes at the opposite electrode, and the overall cell behavior is governed by the spatial separation of oxidation and reduction half-reactions.

Cathodic protection is a major practical application of the concept. It aims to minimize corrosion of metallic structures by making the protected metal a cathode. This is achieved either by attaching sacrificial anodes made of more reactive metals (such as zinc, magnesium, or aluminum) or by using an impressed current from an external power source. The protective effect lowers the metal’s electrochemical potential, reducing dissolution rates. Monitoring and control of the cathodic potential are important to avoid overprotection, which can cause hydrogen embrittlement or coating damage.

Overall, cathodic describes phenomena linked to the cathode, encompassing fundamental electrochemical reactions and applied strategies for corrosion control and surface finishing.