| CAI Fan-fan,HUANG Yan-liang,XING Shao-hua,XU Yong,WANG Xiu-tong.Effect of Barnacle Adhesion on Cathodic Protection of Low Alloy High Strength Steel by Sacrificial Anode[J],52(8):226-236 |
| Effect of Barnacle Adhesion on Cathodic Protection of Low Alloy High Strength Steel by Sacrificial Anode |
| Received:July 29, 2022 Revised:September 19, 2022 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.08.017 |
| KeyWord:barnacle low alloy high strength steel sacrificial anode localized corrosion protection efficiency shielding effect |
| Author | Institution |
| CAI Fan-fan |
Key Laboratory of Marine Environmental Corrosion and Bio-fouling, Institute of Oceanology, Chinese Academy of Science, Shandong Qingdao , China;Open Studio for Marine Corrosion and Protection, Qingdao National Laboratory for Marine Science and Technology, Shandong Qingdao , China;University of Chinese Academy of Sciences, Beijing , China;Center for Ocean Mega-Science, Chinese Academy of Sciences, Shandong Qingdao, China |
| HUANG Yan-liang |
Key Laboratory of Marine Environmental Corrosion and Bio-fouling, Institute of Oceanology, Chinese Academy of Science, Shandong Qingdao , China;Open Studio for Marine Corrosion and Protection, Qingdao National Laboratory for Marine Science and Technology, Shandong Qingdao , China;Center for Ocean Mega-Science, Chinese Academy of Sciences, Shandong Qingdao, China |
| XING Shao-hua |
CSSC Luoyang Ship Material Research Institute, Shandong Qingdao , China |
| XU Yong |
Key Laboratory of Marine Environmental Corrosion and Bio-fouling, Institute of Oceanology, Chinese Academy of Science, Shandong Qingdao , China;Open Studio for Marine Corrosion and Protection, Qingdao National Laboratory for Marine Science and Technology, Shandong Qingdao , China;University of Chinese Academy of Sciences, Beijing , China;Center for Ocean Mega-Science, Chinese Academy of Sciences, Shandong Qingdao, China |
| WANG Xiu-tong |
Key Laboratory of Marine Environmental Corrosion and Bio-fouling, Institute of Oceanology, Chinese Academy of Science, Shandong Qingdao , China;Open Studio for Marine Corrosion and Protection, Qingdao National Laboratory for Marine Science and Technology, Shandong Qingdao , China;Center for Ocean Mega-Science, Chinese Academy of Sciences, Shandong Qingdao, China |
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| Abstract: |
| In order to study the effect of barnacle adhesion on the cathodic protection of low alloy high strength steel with sacrificial anode, comparative experiments were set up in the field site. The low alloy high strength steel used in this study was AISI 4135 steel and the sacrificial anode used in this study was 99.9% pure zinc. The steel was machined into corrosion coupons with two specifications of 350 mm×250 mm×4 mm and 60 mm×15 mm×4 mm respectively. Part of the small corrosion coupons were placed in a cage with plankton-filter of porosity 74 μm to prevent barnacle larva from contacting the surface of the corrosion coupons. Based on past long-term observational experiences, adhered barnacles were fairly abundant at the mid-tide level. Accordingly, the corrosion coupons were fixed at the mid-tide level. After being exposed for 6 and 12 months, the corrosion coupons were analyzed by advanced test techniques, such as X-ray diffraction, Raman spectra, confocal laser scanning microscope and electrochemical tests. Meanwhile, simulating experiments were conducted. The protection current and polarization potential of the low-alloy steel with barnacle adhesion under the protection of sacrificial anodes were monitored. After the experiments, the steel surface deposits were analyzed by scanning electron microscope (SEM) and energy dispersive spectrum (EDS). In the corrosion morphology analysis, the barnacle adhesion area was selected as the observation site of the corrosion coupons with barnacle adhesion, and the observation site of the corrosion coupons without barnacle adhesion was randomly selected. The corrosion morphology results demonstrated that localized corrosion pits formed on the steel substrate regardless of the presence or absence of barnacle adhesion. Meanwhile, it could be found that the steel with barnacle adhesion had larger localized corrosion pits, and tended to form at the edges of the barnacle adhesion. Near-circular raised corrosion morphology was formed in the barnacle adhesion area, while local corrosion pits similar to crevice corrosion were formed at the adhesion edge. The adhesion of barnacle did not affect the composition of corrosion products and deposits. Meanwhile, the content of calcite in the corrosion coupons with barnacle adhesion was higher, mainly from the barnacle shells. Mg2+ could inhibit the formation of calcite, accordingly, the corrosion products on the surface of the corrosion coupons without barnacle adhesion were mainly aragonite. Iron oxides in corrosion products were in the form of Fe3O4, γ-FeOOH, β-FeOOH and Fe5HO8.4H2O. The adhesion of barnacles had no apparent effects on the average corrosion rate of steel under cathodic protection state. Accordingly, the adhesion of barnacles had no apparent effects on the protection efficiency of sacrificial anodes. Polarization curves and current/potential-time curves under sacrificial anode protection suggested that the steel with barnacle adhesion required small polarization current only to reach the required protective potential. The area of the steel affected by the shielding effect of barnacle and the area where localized corrosion occurred were blocked from coming into contact with the external corrosive environment. Accordingly, barnacle adhesion could decrease the effective working area of the steel. Under the condition that the physical properties of the sacrificial anode remained unchanged, the smaller the area of the protected steel, the greater the current on the steel surface, and the closer the potential of the steel was to that of the sacrificial anode. Accordingly, the barnacle-free area of the steel with barnacle adhesion had a higher cathodic protection current (63.9 μA/cm2) than the steel without barnacle adhesion (46.3 μA/cm2), while, the barnacle adhesion area and the localized corrosion area were not effectively protected by cathodic protection. Excessively negative cathodic protection potential promoted hydrogen permeation behavior of the steel. The effects of barnacle adhesion on the hydrogen permeation behavior of steels under sacrificial anode protection are of important research interests both theoretically and practically. |
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