standards and guidelines for communication sites - Radio And ...

STANDARDS AND GUIDELINES FOR COMMUNICATION SITES DISSIMILAR METALS AND CORROSION CONTROL
CAUTION
Extremely fine particles are shed by copper parts, which result in severe corrosive
damage to galvanized parts, even where the copper and galvanized parts are not in
direct contact (IEC 61024-1-2, section 5.2).
• Where a galvanized tower is not protected against precipitation run-off from copper and copper
alloys, the tower ground bus bar (TGB) shall be constructed of tinned copper or other suitable
material.
• Where tinned conductors or galvanized ground rods are used, care shall be exercised during
installation so that surfaces are not damaged. If surfaces of these ground elements are damaged, the
potential for deterioration from galvanic action increases (ANSI T1.313-2003, section 11.5 and
ANSI T1.334-2002, section 13.6).
• Exothermically welded joints on galvanized material shall be coated with a zinc-enriched paint to
prevent corrosion.
• Copper/aluminum joints shall be avoided wherever possible. In cases where they cannot be
avoided, the connections shall be exothermically welded or made using an AL/CU listed bimetallic
transition connector (IEC 61024-1-2, section 5.2). Use a listed conductive anti-oxidant compound
on all mechanical connections (ANSI T1.334-2002, section 9).
• Solid, bare, tinned copper conductor should be used to minimize galvanic corrosion between tower
legs and other parts of the grounding electrode system (ANSI T1.313-2003, section 10.7).
• Grounding connections to galvanized towers shall be exothermally welded whenever possible.
When exothermic welding is not possible, the tower grounding conductor shall be constructed of
tinned-copper (IEC 61024-1-2, section 5.2).
• Select appropriate grounding electrode system components using Table 4-5.
• When soil conditions are not favorable, such as highly acidic or alkaline, grounding electrode
system component corrosion may be reduced by encasing the components in a grounding electrode
encasement material. See “Grounding (Earthing) Electrode Encasement Materials” on page 4-27,
and BS 7430:1998, section 19.6.1, for additional information.
• When soil conditions are not favorable, such as highly acidic or alkaline, grounding electrode
system component corrosion may be reduced by installing electrolytic ground rods encased in a
grounding electrode encasement material. See “Grounding (Earthing) Electrode Encasement
Materials” on page 4-27 and “Electrolytic Ground Rods” on page 4-16.
• When soil conditions are not favorable, such as highly acidic or alkaline, the useful life of a copper
ground rod can be extended by using solid copper ground rods instead of copper-clad rods, if soil
conditions allow driving of the solid copper rod.
• When soil conditions are not favorable, such as highly acidic or alkaline, the useful life of buried
grounding conductors can be extended by using larger conductors, such as 70 mm2 csa (#2/0 AWG)
instead of 35 mm 2 (#2 AWG).
• Use a listed conductive anti-oxidant compound on all mechanical connections (ANSI T1.334-2002,
section 9). The anti-oxidant compound shall be liberally installed between the two metals (see
Figure 4-27 on page 4-40).
• See “Guy Anchor Points” on page 4-54 for information regarding proper grounding techniques to
help minimize galvanic corrosion of the guy anchor.
68P81089E50-B 9/1/05 4-39