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If iron or steel has been seriously appreciably higher than true earth potential. One such system gaining general acceptance  is to require as evidence of protection that the instantaneous-off potential see Where the surfaces to be potential is measured.
In order to avoid Formulae are available from which the output from possible coating disbondment, the protective anodes of various shapes can be estimated see, for current applied should be controlled so as to example , , ,  and . In this, the instantaneous-off making isolated repairs. In the case of impressed current installations, the provision of reference electrodes, as described In some applications, the possibility of in The weatherproof housing on the upper deck.
To prevent this, it is recommended that anodes be d A disturbance of the outer skin of the hull. For a given volume of anode material, used, for example, in the form of a cylindrical rod, the resistance decreases if the length is increased; the effect of diameter being less important. They are, however, frequently used in the form of a thin layer of platinum or platinum alloy about 0. For applications in fully enclosed circulating systems see 8.
It is advisable therefore to comply with these regulations where appropriate. Alternatively, individual control units, each 3. This can usually be carried out on 4. A resistive bond between sleeve is installed by thrust boring, the coating sleeve and carrier pipe, although allowing some should be selected, and appropriate precautions current to reach the carrier pipe, may be taken, to minimize the risk of coating damage insufficient for complete cathodic vs.
When structures such as pipelines are being protected sb impressed current, considerations such as the availability 736-11 power supplies may, however, have an important bearing on the design. Cast iron may Their use in areas susceptible to pollution may therefore be remain effective longer than steel because the discouraged. Soldering, welding and brazing of reinforcing bars involving high heat input is to be avoided but pin brazing or thermit welding could be considered.
Suitable types of coating include: Ep In contrast to the anodic reaction for example is called the protection potential. If the water is stagnant for long periods it 7361–1 seldom suitable and it is normal to use may be necessary to take measures to prevent the impressed current with platinized titanium anodes. For ground conditions where the soil is unsuitable as backfill, consideration should be given to the importation of selected fill, such as clean sand, or to some form of mechanical protection which has a minimal shielding effect on 7361–1 cathodic protection e.
The process is shown for iron in equation 1. Samples of finely ground concrete obtained from the structure either by drilling or by slicing removed cores may be analysed for chloride and cement content. The bonding cable will drain some of the passage of the track circuit signalling current leakage current back into the rail and thence back to between the rails and, hs this case, the traction the point of supply thus ensuring that the structure return current flows in both rails, as it does also receives partial, or sometimes complete, cathodic when there are no track circuits.
Compliance with a British Standard does 73611 of itself confer immunity from legal obligations. Anodes which are to be placed in the midships section of a ship should preferably not be attached to the bbs plating but to the bilge keel; this is recommended by the majority of ship classification societies.
By this means it is possible to reduce greatly the current density required for cathodic protection.
The effects that may will often be supplied from an overhead line. The steel is the structure, and coatings apart, is in contact with the bulk electrolyte. It should be resistant to any chemical or bacterial action to which it might be exposed, and should withstand all temperature variations to which it may be subjected; no blisters should exist and the coating should adhere strongly to the surface to be protected; it should have satisfactory ageing characteristics and adequate mechanical strength.
The gaps should be protection 3761-1 with a single, small electrode. The initial setting of the correct current requires If cathodic protection in service is to be by impressed two or three potential surveys at intervals of a few current, then temporary 731-1 anodes may be days. A schematic representation is shown in Figure 2. Hence all the electrons produced by the anodic reaction are consumed by the cathodic reaction, which is the condition existing on a freely corroding metal surface.
BS Cathodic protection. Code of practice for land and marine applications_图文_百度文库
It has been assumed in the drafting of this British Standard that the execution of its recommendations is entrusted to appropriately qualified and experienced people, for whose guidance it has been prepared.
Tests should normally be made, using Arrangements are normally required to enable the temporarily-installed equipment, to confirm that protection current to be adjusted so that the acceptable conditions can be 7361–1 over the appropriate protection potential is achieved and full range of service conditions, and to determine the maintained. This will need protection. For vessels carrying cargoes that bear a risk of fire or explosion, ship to shore bonding is not recommended see It should be noted, however, that the environment of the metal is altered, for example it becomes more alkaline see above.
Reference As these conditions are usually difficult to attain in should be made to the 736-11 and regulations of the practice, a more satisfactory solution ba to paint the relevant society, e.
Values more positive than these will anaerobic, for example clay soils. Additional points may be required bolt-heads to prevent damage to the insulating in certain critical areas such as pipe-sleeves, or washers when being tightened [see Figure 13 b ].
NOTE In such cases the use of a large mass of bare copper for earthing purposes should be discouraged because of the galvanic cell so created and also the increased cathodic protection current requirements see CP Attention is drawn to the importance of considering any measures necessary to prevent corrosion during the early stages of the design of structures and possible future extensions.
All surface terminal coat internally or replace with non-metallic pipe a boxes should be weatherproof and designed to resist sufficient length of pipe to eliminate entirely the tampering and theft.
BS – Cathodic protection. Code of practice for land and marine applications
Characteristics of the principal anode materials are summarized in Table 3. Other coatings may be more or less susceptible to overprotection, and the structure to soil potential may need to be limited to other values see 3.
Details of tests that are necessary are given in sections 10 and If used in a hazardous area it should minimum needed for protection. Anodes may need to sb designed to suit the geometry of the plant to be protected. For steel structures, the sacrificial anode systems see 9.