How corrosion Occurs in Structured Cabling
Conductors in a cable can go open due to water entering the cable. When the plastic sheath is cut or punctured, water enters the cable. The plastics used in Premises cables and wires are porous as all plastics are. Water seeps into the cable through the sheath. There is battery potential across each working pair in the cable.
Water penetrates the porous plastic insulation and makes contact with the copper wire. Electrons start moving through the conductive water. After some time the water becomes a mild solution of sulphuric acid. When water gets between the tip and ring conductors, it forms a high resistance leakage path between exposed metal in the two conductors. The battery voltage on the ring conductor sets up an electrolysis path.
The copper from the tip conductor is eaten away and deposited on the ring conductor. After a period of weeks or months, the tip conductor is completely eaten away and the circuit is opened. The conduction path between ring and tip means that battery voltage appears on the tip, even after the tip conductor opens.
Unless the conductors are damaged at the same time as the sheath, the effects of the water may not be seen for several months. The conductor trouble may not be in the same place as the damage to the sheath. The deterioration of the service will be gradual. The first indication of trouble will probably be from a customer complaint.
When water enters a cable, there is no noticeable effect right away for low frequency applications and the water will travel along the cable to its lowest point. The water may step up to several hundred feet along the cable to where the insulation is imperfect. Should the water reach a conductor through a pinhole in the insulation, a high resistance leakage path will develop from the ring-to-tip.
For high frequency applications, failures will be very rapid, within a few hours. Moisture may also penetrate the cable sheath through diffusion.