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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Cathodic protection | 4/5 | https://en.wikipedia.org/wiki/Cathodic_protection | reference | science, encyclopedia | 2026-05-05T10:46:35.089302+00:00 | kb-cron |
=== Automobiles === Several companies market electronic devices claiming to mitigate corrosion for automobiles and trucks. Corrosion control professionals find they do not work. There is no peer reviewed scientific testing and validation supporting the use of the devices. In 1996 the FTC ordered David McCready, a person that sold devices claiming to protect cars from corrosion, to pay restitution and banned the names "Rust Buster" and "Rust Evader." Under section 74.01(1) (b) of the Competition Act Canada, no performance claims about a product or its effectiveness can be done unless it can be proven that they are based on adequate and proper tests. The Competition Bureau Canada proceeded to investigate several companies selling electronic corrosion devices in Canada. Some were forced to withdraw their product from the market as they could not support their claims scientifically.
== Testing == Electrode potential is measured with reference electrodes. Copper–copper sulphate electrodes are used for structures in contact with soil or fresh water. Silver/silver chloride/seawater electrodes or pure zinc electrodes are used for seawater applications. The methods are described in EN 13509:2003 and NACE TM0497 along with the sources of error in the voltage that appears on the display of the meter. Interpretation of electrode potential measurements to determine the potential at the interface between the anode of the corrosion cell and the electrolyte requires training and cannot be expected to match the accuracy of measurements done in laboratory work.
== Problems ==
=== Production of hydrogen === A side effect of improperly applied cathodic protection is the production of atomic hydrogen, leading to its absorption in the protected metal and subsequent hydrogen embrittlement of welds and materials with high hardness. Under normal conditions, the atomic hydrogen will combine at the metal surface to create hydrogen gas, which cannot penetrate the metal. Hydrogen atoms, however, are small enough to pass through the crystalline steel structure, and can lead in some cases to hydrogen embrittlement.
=== Cathodic disbonding === This is a process of disbondment of protective coatings from the protected structure (cathode) due to the formation of hydrogen ions over the surface of the protected material (cathode). Disbonding can be exacerbated by an increase in alkali ions and an increase in cathodic polarization. The degree of disbonding is also reliant on the type of coating, with some coatings affected more than others. Cathodic protection systems should be operated so that the structure does not become excessively polarized, since this also promotes disbonding due to excessively negative potentials. Cathodic disbonding occurs rapidly in pipelines that contain hot fluids because the process is accelerated by heat flow.
=== Cathodic shielding === Effectiveness of cathodic protection (CP) systems on steel pipelines can be impaired by the use of solid film backed dielectric coatings such as polyethylene tapes, shrinkable pipeline sleeves, and factory applied single or multiple solid film coatings. This phenomenon occurs because of the high electrical resistivity of these film backings. Protective electric current from the cathodic protection system is blocked or shielded from reaching the underlying metal by the highly resistive film backing. Cathodic shielding was first defined in the 1980s as being a problem, and technical papers on the subject have been regularly published since then. A 1999 report concerning a 20,600 bbl (3,280 m3) spill from a Saskatchewan crude oil line contains an excellent definition of the cathodic shielding problem:
The triple situation of disbondment of the (corrosion) coating, the dielectric nature of the coating and the unique electrochemical environment established under the exterior coating, which acts as a shield to the electrical CP current, is referred to as CP shielding. The combination of tenting and disbondment permits a corrosive environment around the outside of the pipe to enter into the void between the exterior coating and the pipe surface. With the development of this CP shielding phenomenon, impressed current from the CP system cannot access exposed metal under the exterior coating to protect the pipe surface from the consequences of an aggressive corrosive environment. The CP shielding phenomenon induces changes in the potential gradient of the CP system across the exterior coating, which are further pronounced in areas of insufficient or sub-standard CP current emanating from the pipeline's CP system. This produces an area on the pipeline of insufficient CP defense against metal loss aggravated by an exterior corrosive environment.
Cathodic shielding is referenced in a number of the standards listed below. Newly issued USDOT regulation Title 49 CFR 192.112, in the section for Additional design requirements for steel pipe using alternative maximum allowable operating pressure requires that "The pipe must be protected against external corrosion by a non-shielding coating" (see coatings section on standard). Also, the NACE SP0169:2007 standard defines shielding in section 2, cautions against the use of materials that create electrical shielding in section 4.2.3, cautions against use of external coatings that create electrical shielding in section 5.1.2.3, and instructs readers to take "appropriate action" when the effects of electrical shielding of cathodic protection current are detected on an operating pipeline in section 10.9.
== Certification == In many countries, having a related CP certificate is recommended or, in some cases, mandatory for doing a CP job, from field test to design. There are different certification bodies and evaluation methods, but two of them are more common: AMPP certification and ISO 15257. AMPP cathodic protection certification has four levels: Tester, Technician, Technologist, and Specialist. ISO 15257 has five levels: Four levels close to the AMPP definition, plus another level for those who have made a scientific contribution.
=== Countries ===
==== France ==== The main center for cathodic protection certification in France and some French language countries is CEFRACOR.
==== Germany ==== fkks cert GmbH (owned by fkks: Fachverband Kathodischer Korrosionsschutz e.V., trans. German Professional Association for Cathodic Protection specialists) is an accredited certification scheme in the field of cathodic corrosion protection.
==== Italy ==== Three different bodies will provide cathodic protection certificates based on ISO 15257: APCERT, CICPND, and RINA.