Journal of Materials Science and Engineering B 3 (5) (2013) 314-321 Evaluation of Effect of Eddy Currents in PLC Influenced by Atmospheric Corrosion in the Electronics Industry Gustavo López Badilla 1 , Elizabeth Romero Samaniego 2 , Sandra Luz Toledo Perea 2 , Miriam Maleny García Castrellon 3 and Luis Alberto Gameros Rios 3 1. Researcher-Academic, Technological Institute of Mexicali (TIM), Mexicali, Baja California, México 2. Researcher-Academic, Technological Institute of Ensenada (TIE), Ensenada, Baja California, México 3. Students of Electronic Engineering, Technological Institute of Mexicali (TIM), Mexicali, B.C., México Received: March 22, 2013 / Accepted: April 15, 2013 / Published: May 25, 2013. Abstract: Inductive proximity sensors contain an internal coil. When a current flow through it, a magnetic field is generated, which has the direction of the electric currents involved in it, as electrical flow in the input or output area. The coil or winding of the inductive sensor induces Foucault currents in the material to be detected, that are originated by eddy currents. These electrical flows generate a magnetic field, which opposes to the sensor coil, causing a reduction in the inductance of micro inductors of electronic devices. This reduction of the internal inductance originates bad function in the micro inductors used in the programming logic controller (PLC). This PLC is in the manufacturing processes of the electronics industry and reduces their operation yielding. Sometimes the actuators of these electronic systems not operate correctly, and causing stops in the activities of industrial equipments and machines, being a factor of economic losses. A study of micro evaluation of these inductors which are elements of the relays of PLC was made to determine the influence of corrosion in these components. The analysis showed micro corrosion in these devices with images obtained of the scanning electron microscopy (SEM) and also was made a correlation of the climatic factors as relative humidity (RH) and temperature with the corrosion rate (CR). The evaluation was made in indoor of an industrial plant which fabricate microelectronic components in Mexicali city. The major factors, which cause an adverse effect in the operation of PLC of this industrial plant was the humidity and sulfurs, which originates the deterioration of components of PLC. The study was made from 2010 to 2011. Key words: Foucault currents, PLC, micro corrosion, electronics industry. 1. Introduction In the electromagnetic process, the induced current is forced to follow well defined paths through wires made of conductive material. The electrical equipment are formed by parts, pieces of conductor moving in a magnetic field or are located in a variable magnetic field, leading to circulating currents induced by the conductor volume. These are called eddy currents or Foucault currents. When placing a piece of metal in a magnetic field varying with time B(t), generates an electric field that produces a motion of free charges in Corresponding author: Gustavo López Badilla, Dr., research fields: environment, corrosion, materials and surface analysis. E-mail: glopezbadilla@yahoo.com. the metal conductor, causing an electromagnetic field as is mentioned in the next mathematical equation: ර ·ܧ ൌ െ   ݐ න ·ܤdS ሺ1ሻ ୱ This Foucault current generates variations in the electromagnetic systems used in the electronics industry [1]. 1.1 Foucault Currents The eddy currents occur when an electrical conductor passes through a variable magnetic field, or vice versa. The relative movement causes an electron flow or current induced within the electrical conductor. These circular currents create electromagnetic fields DAVID PUBLISHING D