In electrical engineering

Electrical engineering

Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after commercialization of the electric telegraph and electrical...

, a wetting current (or sealing current) is the minimum current needing to flow through a mechanical switch

Switch

In electronics, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another....

 or relay while it is operated in order to break through any film of oxidation that may have been deposited on the switch contacts. The film (contact oxidation) occurs often in areas with high humidity

Humidity

Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...

. Providing a sufficient amount of wetting current is a crucial step in designing systems

Control engineering

Control engineering or Control systems engineering is the engineering discipline that applies control theory to design systems with predictable behaviors...

 that use delicate switches with small contact pressure as sensor inputs. Failing to do this might result in switches remaining electically 'open' due to contact oxidation.