MIL-HDBK-1004/10
The presence of other cathodic protection systems in the area should be
particularly noted as the installation of an additional cathodic protection
system can affect the operation of existing systems. The review of the site
drawings should also include the location of sources of ac power for impressed
current systems and possible location of anode ground beds.
Field Surveys. A field survey at the site is usually required in
4.2.2
order to establish the actual environmental conditions which will be
encountered. For submerged systems, all that is normally required is a water
analysis, or current requirement test, and a site survey to establish the
presence of interfering structures or other special circumstances. For buried
systems, more extensive information is required.
Water Analysis. Samples of water should be analyzed for pH,
4.2.2.1
chloride, sulfate, and resistivity at a minimum. Other factors such as
hardness may be pertinent to the specific circumstance.
Soil Characteristics. For buried systems, soil characteristics
4.2.2.2
must be defined in order to establish the requirements for protection.
Sulfide, sulfate, chloride, pH, and other chemical constituents will affect
the current requirements necessary for protection and protection criteria for
some materials. Current requirements for typical environments are given in
Tables 1 and 2. Protection criteria are given in para. 3.3.
Table 1
Current Requirements for Cathodic Protection of Bare Steel
ENVIRONMENT
MILLIAMPERES PER
SQUARE FOOT (mA/ft)
Soil with resistivity <1,000 ohm-cm
6.0
-
25.0
Soil with resistivity 1,000 - 10,000 ohm-cm
3.0
-
6.0
Soil with resistivity 10,000 - 30,000 ohm-cm
2.0
-
3.0
Soil with resistivity >30,000 ohm-cm
1.0
-
2.0
Highly aggressive soil with anaerobic bacteria
15.0
-
40.0
Still fresh water
2.0
-
4.0
Moving fresh water
4.0
-
6.0
Turbulent fresh water
5.0
-
15.0
Hot fresh water
5.0
-
15.0
Still seawater
1.0
-
3.0
Moving seawater
3.0
-
25.0
Concrete
0.5
-
1.5
20
Previous Page
