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A method for cathodic protection of bare steel structures in seawater

A cathodic protection and bare steel technology, which is applied in the field of cathodic protection of steel structures, can solve the problems of high requirements on the surface state of steel structures, accelerate coating cathodic stripping, shorten the service life of coatings, etc., and achieve saving the amount of sacrificial anodes, coating The effect of process simplification, process saving and construction time

Active Publication Date: 2020-11-20
OCEAN UNIV OF CHINA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the coating requires a relatively complicated process, high requirements on the surface state of the steel structure, complicated pre-treatment, long construction period, high cost, and an excessively negative cathodic protection potential will accelerate the cathodic stripping of the coating and shorten the coating life. service life

Method used

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  • A method for cathodic protection of bare steel structures in seawater
  • A method for cathodic protection of bare steel structures in seawater
  • A method for cathodic protection of bare steel structures in seawater

Examples

Experimental program
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Effect test

Embodiment 1

[0042] Example 1: Cathodic protection method for temporary coating of bare steel

[0043] A protection area of ​​9300m in the seawater of the jacket structure of a Bohai oil production platform 2 , design life 20a, seawater resistivity ρ = 20Ω·cm. The Al-Zn-In sacrificial anode is selected and has the following performance parameters: driving voltage ΔE=0.25V, sacrificial anode working potential of -1.05V (vs. SCE), and cathode polarization potential of -0.80V (vs. SCE). The designed anode size is (250+260)×260×(2100+2300), and the initial equivalent radius of the anode is r=16.4cm. The anode core is a Q235 steel pipe of Φ114×8.5×3360, and the radius of the anode core is r corr = 5.7 cm. The net weight of the anode is 333kg. The electrochemical capacity of the sacrificial anode is ε=2500Ah / kg.

[0044] Thus, the initial current of each anode is obtained as:

[0045]

[0046] According to the NACE standard, the recommended initial current density is 100mA / m 2 , mid-te...

Embodiment 2

[0090] Example 2: Cathodic protection method for temporary coating of bare steel

[0091] Take a certain jacket in the South China Sea as an example.

[0092] A protection area of ​​95,000m in seawater for the jacket structure of an oil production platform in the South China Sea 2 , Design life 31a, seawater resistivity ρ = 25Ω·cm. Al-Zn-In sacrificial anode is selected, which has the following performance parameters: driving voltage ΔE=0.25V, sacrificial anode working potential is -1.05V (vs.Ag / AgCl / sea water), cathode polarization potential is -0.80V (vs. Ag / AgCl / sea water). The designed anode size is (250+260)×260×(3000+3100), and the initial equivalent radius of the anode is r=16.4cm. The anode core is a Q235 steel pipe of Φ114×8.5×4390, and the radius of the anode core is r corr = 5.7 cm. The net weight of the anode is 461.7kg. The electrochemical capacity of the sacrificial anode is ε=2000Ah / kg.

[0093] Thus, the initial current of each anode is obtained as:

[...

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Abstract

The invention discloses a method for protecting cathodes of a bare steel structure in seawater. The method comprises the following steps that (1) first the type of sacrificial anodes is selected, thenthe current from each sacrificial anode is calculated, the number N1 of the sacrificial anodes is calculated by the medium-term current density and the electrochemical capacity of the sacrificial anodes, the number N2 of needed anodes is calculated by the current from terminal anodes, and a larger value is selected by comparing N1 with N2; (2), a temporary coating is applied to the surface of a protected bare steel structure; and (3) sacrificial anodes with the number calculated in the step (1) are welded on the protected bare steel structure according to a general construction method. Compared with a traditional method of protecting cathodes by sacrificial anodes, the method for protecting the cathodes of the bare steel structure in the seawater can save anode consumption; at the same time, the bearing capacity of the structure is reduced, the cost is saved, and the safety is increased; and compared with a traditional coating and cathodic protection combined protection technology, the coating process is simplified, the requirement of quality of coating is low, a role is played in the initial stage, the process and construction occupation time are saved, and the cost is saved.

Description

technical field [0001] The invention relates to a method for cathodic protection of steel structures, in particular to a method for cathodic protection of bare steel structures in seawater. Background technique [0002] Metal structures far away from the coast are often protected by sacrificial anode cathodic protection. However, in the process of cathodic protection, there is a contradiction between the initial high current density and the medium-term low current density, and the former is about twice as much as the latter. In view of the contradiction between the initial large current density and the mid-term low current density of cathodic protection of marine structures, the currently adopted measures are: (1) Design and calculate according to the initial and mid-term current densities respectively, and then take the larger value. The harm of doing so is obvious: wasting resources; increasing the carrying capacity, bringing security risks. (2) Use a small-mass anode to...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C23F13/04C23F13/16
CPCC23F13/04C23F13/16C23F2213/20C23F2213/31
Inventor 杜敏王焕焕刘思奇高荣杰
Owner OCEAN UNIV OF CHINA