Cathodal

Cathodal is the adjective relating to the cathode, the electrode involved in reduction in electrochemical reactions. The term is used across disciplines to indicate either the electrode itself or processes occurring at it. Polarity conventions vary with context: in galvanic (voltaic) cells the cathode is positive, while in electrolytic cells the cathode is negative, connected to the external power supply's negative terminal; the anode plays the opposite role in each case.

In electrochemistry and electronics, the cathode is the site of reduction. Many devices and processes are named for the cathode's identity. For example, cathodic deposition and electroplating involve reduction of metal ions at the cathode onto a surface, producing a metal coating. In rechargeable cells, the cathode material is a key determinant of voltage, capacity, and cycle stability.

Cathodic protection is a corrosion-control technique in which more easily oxidized metals act as sacrificial anodes to supply electrons to a protected metal structure, making that metal the cathode and reducing its tendency to oxidize. Related processes include cathodic polarization and cathodic arc deposition, used in coatings and surface engineering.

In neuroscience and medicine, cathodal stimulation uses a negative electrode to deliver current through tissue. Under the cathode, extracellular currents generally hyperpolarize nearby neurons and decrease cortical excitability, whereas anodal stimulation tends to increase excitability; practical applications include transcranial direct current stimulation and other neuromodulation approaches, with effects depending on electrode montage, duration, and intensity.

See also Anode, Electrochemistry, Cathode.