MIL-HDBK-1004/10
Section 4:
CATHODIC PROTECTION SYSTEM DESIGN PRINCIPLES
Introduction. As cathodic protection is applied to the prevention
4.1
of corrosion of a wide variety of structures in a wide variety of
environments, each situation will require special consideration. There are
fundamental procedures that should be followed in each case. However, the
actual functioning of any cathodic protection system is dependent upon the
condition of the local environment at each point on the surface of the
structure to be protected, and upon the actual level of protective current
supplied to each point of the structure. A predesign survey, as outlined in
Appendix A, is essential for determining environmental and structural
considerations for the design of any cathodic protection system. While a good
approximation of the system requirements can be obtained through field surveys
and a good approximation of current distribution can be made when allowances
are made for differing environments and interfering structures, the installed
system will, at a minimum, require initial adjustments to balance the system
and periodic adjustments to maintain that balance. In some cases,
particularly in the case of previously unknown interfering metallic structures
in the vicinity of the structure being protected, modifications to the
initially designed system may be required in order to achieve adequate
protection. The design and operation of cathodic protection systems is an
iterative procedure.
General Design Procedures. The general design procedure for both
4.2
sacrificial anode and impressed current systems is similar. First the amount
of protective current is determined, then the best means of applying the
current to the structure is established. In many cases both sacrificial and
impressed current systems are feasible and an initial approximate design is
prepared for each type of system in order to select the most appropriate type
of system for the particular application.
Drawings and Specifications. A review of pertinent drawings and
4.2.1
specifications for the structure being protected and for the site should be
made in order to obtain information necessary for the design of a cathodic
protection system. Actual conditions ("As-Built") should be verified since
structurally and operationally insignificant factors, such as contact between
buried structures (shorts), can have a great effect upon the operation of a
cathodic protection system.
Drawings and Specifications for the Structure to be Protected. The
4.2.1.1
size, shape, material, and surface condition of the structure to be protected
must be established in order to design an effective cathodic protection
system. The size and shape are usually established by the appropriate
drawings for the installation. The material and surface conditions,
particularly the presence and quality of protective coatings, are usually
established by the specifications for the installation. For a previously
installed system, the condition of the protective coatings may have to be
established during a field survey.
Site Drawings. A site drawing including all other metallic
4.2.1.2
structures in the vicinity should also be reviewed to establish the presence
and locations of other structures which may affect the operation of the system
being designed.
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