Criterion of cathodic protection effect

1) common steel cathodic protection criterion: ◆ when the cathodic protection is applied, the negative potential shift of the protected structure reaches at least -850mV or more negative (relative saturated copper sulfate reference electrode CSE). ◆ The negative polarization potential relative to the saturated copper sulfate reference electrode is at least 850mV. ◆ The minimum cathodic polarization value between the structure surface and the stable reference electrode in contact with the electrolyte is 100mV. ◆ In the presence of sulfate-reducing bacteria, the potential of the protected structure is negatively shifted to 950mV(CSE) or more. 2) aluminum alloy cathodic protection criterion: ◆ The minimum cathodic polarization value between the structure and the stable reference electrode in the electrolyte is 100mV, the criterion is applicable to the polarization establishment or decay process. ◆ Polarization potential should not be negative to -1200mV (CSE). 3) Copper alloy cathodic protection criteria: ◆ The minimum cathodic polarization value of stable reference electrode in the structure and electrolyte is 100mV. Polarization establishment or decay processes can be applied. 4) dissimilar metal cathodic protection criterion: ◆ The negative voltage between the metal surface and the stable reference electrode in the electrolyte is equal to the protective potential of the metal in the anode area with the strongest activity. 5) high strength steel cathodic protection criteria: ◆ more than 700MPa steel corrosion rate is reduced to 0.0001mm/a protection potential is -760 ~ -790mv (Ag/AgCl). ◆ In the presence of sulfate reducing bacteria in the environment, steel yield strength is greater than 700MPa, the protection potential should be in the range of 800-950mV(Ag/AgCl). ◆ For steel with yield strength greater than 800MPa, the protection potential should not be lower than -800mV(Ag/AgCl).