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The application of platinum or platinum should not offer excessive resistance to flow.
In this, the instantaneous-off potential is measured. Off-shore applications are to be covered in Part 2 see foreword. In providing cathodic protection within confined Equipment for power supply is described in 3. The output also depends on the driving potential and thus upon the anode materials 3. If isolation and separate earthing is required, it is feasible to design special joints to interrupt the continuity of the cable sheath.
This is because of allow corrosion to occur. Where mains power is not available, other types of generator such as diesel, solar, wind, thermoelectric or turbine may be used. In any event, as a general guide, it should be an electrolyte having a suitable resistivity should not exceed the level necessary to produce and not aggressive with respect to the anode an instantaneous-off potential more negative material.
The decision should current systems and sometimes with full hull take into account factors that determine the bulk of schemes an allowance should be made in the sacrificial anode material which would be required, system design for the additional current that will and the importance attached to increased drag.
Anodes or groundbeds should be sited where the soil resistivity is as low as possible compatible with a suitable position in relation to the structure to be protected. Where a protected structure, or the anode s or groundbed slie near to other buried or immersed metallic structures that are not fully insulated from earth, the latter secondary structures may, at certain points, pick up a proportion of the protective current due to potential gradients in the soil or water and return it to earth at other points.
Storage tank bottoms are generally constructed by lap welding individual plates and are therefore electrically continuous.
Steel corrosion produces expansive forces which generate cracks in the concrete. Cathodic protection is a means of preventing the corrosion of most metals wherever they are in contact with a mass of water or moist materials.
If the isolated section is so placed that inorganic fibres, and petroleum wax impregnated the required continuity of the structure is fabric ba are also used. The method of gasket should ensure that no recess is formed attachment to the pipeline will vary according to internally between flanges in which material may circumstances, but whatever method is selected, accumulate that could bridge the insulating gap.
The criterion for protection is that the cathodic protection systems is described and the potential of the metal with respect to the electrolyte general features of materials and equipment are immediately adjacent to it should be, at all indicated. Such connections and the connection to the structure to be protected should be securely made and have low electrical resistance.
Zinc has been sprayed on concrete and used as continuous anodes.
Application to ships 6. If cathodic protection is to be applied, for example, because of evidence of chloride intrusion see 5. This does not apply sb plant protected internally by cathodic protection. Formation of gaseous cathodic products which are unable to diffuse away from the interface, could lead to disruption bw this interfacial adhesion. Their output cannot be controlled but there is 8 a tendency for their current to be self-adjusting because, if conditions change such that the metal to be protected becomes less negative, driving e.
BS Cathodic protection. Code of practice for land and marine applications_图文_百度文库
Application to buried structures 4. It has been found that water as is indicated in Table 1. The final current requirement will usually be much less owing to long term polarization effects. Soldering, welding and brazing of reinforcing bars involving high heat input is to be avoided but pin brazing or thermit welding could be considered.
In to maintain cathodic protection.
BS – Cathodic protection. Code of practice for land and marine applications
Both tend to make the electrolyte alkaline near the cathode excess of hydroxyl ions over hydrogen ions: General principles of cathodic protection C. Entries in Table 4 which are of special importance with respect to ships are 6891011 and At one time, chlorides were in both cases, the criteria for protection differ also used, 73661-1 the form of calcium chloride, to substantially from conventional cathodic protection accelerate the initial set of concrete. The choice between the two systems in any particular application will depend upon a detailed assessment of the technical and economic factors involved see 3.
Superseded by BS EN The metals aluminium, titanium and a magnesium most electronegative of the tantalum also form highly resistant and adherent materials listed ; oxide films which restrict the rate at which metal b zinc; ions can pass into solution.