Editing Outside plant (section)

===Corrosion resistance===
Corrosion in outside plant telecommunications network components is caused by exposure to the effects of temperature, humidity, electrical power, and contaminants. Corrosion resistance criteria for these network components are based on the environments to which they are exposed.

Outside plant environments can be above-ground, underground, buried, or underwater. Industry requirements document [[Telcordia]] [http://telecom-info.njdepot.ericsson.net/site-cgi/ido/docs.cgi?ID=SEARCH&DOCUMENT=GR-2836& GR-2836] defines these environments and provides corrosion resistance criteria for the telecommunications equipment in each.<ref>[http://telecom-info.njdepot.ericsson.net/site-cgi/ido/docs.cgi?ID=SEARCH&DOCUMENT=GR-2836& GR-2836-CORE, ''Generic Requirements for Assuring Corrosion Resistance of Telecommunication Equipment in the Outside Plant,''] Telcordia.</ref> It also includes references to various associated [[ASTM]] Standards.

====Above-ground plant====
Above-ground plant includes all the telecommunications equipment physically located on or above the ground. This includes enclosures such as huts, cabinets, and pedestals, and the equipment mounted therein. It also includes pole-mounted equipment and cases, and pole-line hardware.

Above-ground plant can be exposed to extreme temperatures, and to humidity that varies with the seasons and with daily temperature changes. When humidity condenses on the surfaces of outdoor apparatus or equipment, the corrosivity of the moisture layer can be increased by industrial pollutants that render the condensate moisture corrosive. In sea coastal areas, wind-borne, salt-laden water droplets can deposit on exposed components.

Near large cultivated areas, where fertilizers are applied by airplanes, the wind may carry nitrates, phosphates, and ammonium compounds to settle on metallic components of the above-ground telephone plant. Similarly, in residential areas, lawn fertilizers and herbicides can cause corrosion. In regions with snow, the salts used to melt snow and ice on roadways can accelerate corrosion. Under extreme conditions, pedestals and cabinets may be flooded with water that contains mud and corrosive salts. Corrosion of these flooded components may be accelerated by the presence of dc voltages used to power the networks. Secretions from insects can also accelerate corrosion. Finally, chewing by rodents may expose metallic components, normally protected by a polymer or paint coating, to a corrosive environment.

====Underground plant====
Underground plant includes all the telecommunications equipment installed in underground structures such as utility holes, Controlled Environment Vaults (CEVs), and ducts, along with associated hardware. Underground plant can be exposed to waters containing water-soluble salts of the native soil. Utility holes often show evidence of corrosion of support hardware and bonding ribbons that is caused by sulfate-reducing bacteria. The environment in utility holes and ducts can be made corrosive by man-made chemicals such as industrial effluent, fertilizers, and de-icing salts. Protective plastic coatings and cable jackets can rapidly deteriorate from leaking steam pipes present in many urban areas and from gasoline leaking from underground storage tanks.

The most aggressive contributor to corrosion of underground plant is dc stray current from electrified rail transportation systems, cathodic protection rectifiers, or welding and mining operations. Although such dc currents are mostly dealt with “after the fact” using protective systems (e.g., low resistance bonds, reverse current switches, cathodic protection), some of the protection has to be included at the manufacturing stage. This protection may include insulating covers on cable shields, or nonmetallic components or coatings for apparatus.

====Buried plant====
Buried plant consists of telecommunications equipment such as cables, splice closures, lower parts of pedestals, and grounding systems directly buried in the soil. Buried plant can be exposed to the same corrosive environment as underground plant. In addition, attack by gophers can expose underlying components to corrosion attack.

====Underwater plant====
Underwater plant includes all telecommunications equipment located beneath the surface of a body of water. This includes cables and repeaters. The water can range from relatively pure, to brackish, to badly contaminated with industrial effluent.