scope:

Scope and Limitations

This standard practice describes appropriate prevention and mitigation measures that can be applied to steel reinforced concrete (RC) and prestressed concrete (PC) structures that are, or can be, exposed to stray-currents from external sources in order to minimize or eliminate stray-current corrosion. This standard practice addresses only steel corrosion related issues, and does not deal with issues of safety and hazards to people or structures associated with DC and AC voltages; these are covered in national standards and regulations, such as EN 50443 and EN 50122-1.^3,4

Stray-current corrosion damage can appear after only a short time of exposure to stray currents and is highly dependent on a large number of variables,¹ which should be determined during the planning or design stage of a structure. It is important to make provisions for incorporation of protection and mitigation measures and/ or monitoring techniques at an early stage in the design (Sections 3, 4 and 6) and monitor the effect of these protection and mitigation measures regularly (Sections 5, 7 and 8).

Measurement techniques used to determine stray current effects on a structure are described in Section 4. This standard practice also gives measurement criteria for determining when countermeasures must be applied.

Monitoring for stray currents is important during the service life of a structure. If stray currents are detected, proper mitigation techniques should be selected to avoid corrosion from stray current interference. Mitigation techniques in an existing structure are discussed in Section 6.

This standard practice considers only stray current effects from sources external to the structure or structural elements. In the case that a system (such as, but not limited to, CP, ECE, realkalization) is going to be installed in a structure, the possibility of generating stray current interference and their effects to other parts of the structure or to neighboring structures shall be considered. When stray current interference from such a system is expected to be unacceptable, measures shall be taken and appropriate standards shall be followed to ensure that stray current interference to other parts of the structure or to neighboring structures is minimized. Electrical continuity requirements for CP installation in RC structures are described in NACE SP0290.⁵ The effect of CP on prestressing steels is a separate and important issue discussed in NACE Publication 01102.⁶ For high-voltage DC transmission systems, information on controlling stray currents is given in NACE SP0177.² Proper measures taken on DC rail systems to avoid the generation of stray currents is given in NACE Publication 10B189.⁷

The measures described in this standard practice are intended solely for protection against stray-current corrosion. Galvanic corrosion of steel reinforcement that could result from intentional contact of steel with other metals, such as during grounding for safety and stray current mitigation measures, should be carefully considered. For effective protection against other types of corrosion, other measures should be applied as they are described in other standards.^5,8-11

The provisions of this standard practice are intended to be applied under the direct supervision of competent professionals, who are qualified to engage in the practice of corrosion control of stray-current corrosion in RC and PC structures. Such professionals may be, but are not limited to, registered professional engineers or persons certified by NACE as corrosion specialists or CP specialists, if their professional activities include suitable experience of corrosion control from stray-currents in RC and PC structures.

The practices and procedures described in this standard practice must ensure a safe and healthy environment for personnel. All personnel shall be instructed concerning any electrical hazards when working in an area where high voltage or current may be present and shall be required to follow safe working practices at all times, as set by local and state standards and regulations.

Corrosion control work shall be conducted in compliance with the safety requirements as outlined in the National Electrical Safety Code (NESC)¹² set forth by the Institute of Electrical and Electronics Engineers (IEEE),⁽²⁾ and state and local codes. The international user should follow the safety requirements and codes in his/her country.

⁽¹⁾ European Committee for Standardization (CEN), Avenue Marnix 17, B-1000 Brussels, Belgium.

⁽²⁾ Institute of Electrical and Electronics Engineers (IEEE), 3 Park Ave., 17th Floor, New York, NY 10016-5997.

⁽³⁾ ASTM International (ASTM), 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959.

⁽⁴⁾ International Organization for Standardization (ISO), Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva, Switzerland.

⁽⁵⁾ Bundesamt für Strassen (ASTRA), Mühlestrasse 2, CH-3003 Bern, Switzerland.