In the design of impressed current cathodic protection, we must select the protection parameters scientifically and reasonably. Generally, the main parameters selected are the protection current density and protection potential, which is very important for whether the protection potential can achieve the expected effect.
If the selection of design parameters is too low, the structure can not be fully protected. However, if the parameters are too high, the over protection phenomenon will often occur, which will damage the integrity of the anticorrosive coating by hydrogen induced peeling, resulting in serious corrosion damage and further affecting the normal operation of cathodic protection system. No matter which type of parameter selection is unreasonable, it will affect the efficiency and economy of cathodic protection system. The problem of over protection should be avoided especially for the design of impressed current cathodic protection.
The protection current density is related to the type of metal material, surface state and environmental conditions. Some are also related to working conditions. Some factors should also consider the influence of seasonal variation and time effect.
In the same corrosion system, the protective potential and current density are interdependent. The selection and determination of protection potential include setting a given potential for the potentiostat, controlling the electrode potential of the structure at the designated reference electrode position through the internal comparison circuit of the potentiostat; and determining the effect of cathodic protection by testing and judging the effect of cathodic protection, and knowing whether the surface potential of the structure has reached the protection potential value required or specified by the criterion by measuring the potential. The selection of the minimum protection potential value of the structure should be determined according to the relevant standards or specifications. Under special conditions, the previous examples and experience can be referred to.
In the design of cathodic protection, in order to ensure the effectiveness of cathodic protection, the protection potential range must be determined first according to the protected structure and its environmental conditions, and then various process calculations can be carried out.
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