| WU Guang-chun,LI De-ming,ZHANG Meng-meng.Alternating Current on Corrosion Behavior of X80 Steel[J],51(6):307-316 |
| Alternating Current on Corrosion Behavior of X80 Steel |
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| DOI：10.16490/j.cnki.issn.1001-3660.2022.06.029 |
| KeyWord:X80 steel AC current density corrosion behavior CP |
| Author | Institution |
| WU Guang-chun |
Safetech Research Institute, Beijing , China |
| LI De-ming |
Shanghai Natural Gas Pipeline Network Co., Ltd., Shanghai , China |
| ZHANG Meng-meng |
Safetech Research Institute, Beijing , China |
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| Abstract: |
| This paper aims to clarify the influence of alternating current on the electrochemical kinetic parameters of corrosion process, corrosion development and corrosion rate of X80 steel. The influence of AC on the electrochemical kinetic parameters of X80 steel corrosion was analyzed by using the dynamic potential polarization test of X80 steel specimens under the action of AC current density; The indoor corrosion weightlessness simulation test was built and the cathodic protection and AC interference parameters of the specimens were monitored during the test to analyze the influence of AC on the corrosion rate, diffusion resistance and DC current density of X80 steel specimens; The corrosion morphology and the change process of corrosion product composition of X80 steel specimens under the action of AC were analyzed by using the combination of Raman spectroscopy test and microscopic morphology. The results show that the A.C. negatives the free-corrosion potential of X80, when the AC current density is less than 100 A/m2, the negative shift amplitude increases significantly with the increasement of the AC current density, and when the AC current density is greater than 100 A/m2, the corrosion potential is close to each other. The free-corrosion current density shows the same rule as the free-corrosion potential, and no significant change in the slope of the cathode and anode Tafel. When the polarization potential of the X80 steel sample is negatively shifted from –0.428 V (vs. SCE) to –0.928 V, the diffusion resistance of the sample with the surface area of 6.5 cm2 and 1.0 cm2 decreases from 0.063, 0.048 Ω.m2 to 0.051, 0.036 Ω.m2. When the alternating current density increases from 0 to 300 A/m2, the average DC current density corresponding to the polarization potentials of –0.428, –0.878 and –0.928 V increased 0.83, 1.72 and 2.30 times, respectively. The alternating current accelerated the corrosion of X80. When the alternating current density increased from 0 A/m2 to 300 A/m2, the corrosion rate increased significantly and then slowly. The corrosion morphology shows that as the AC current density increased, the corrosion morphology changes from uniform corrosion to pitting corrosion and finally to local corrosion. When the AC current density reaches 200 and 300 A/m2, γ-FeOOH appears in the corrosion products of the specimens. These results show that AC promoted the cathode and anode reaction process of X80 steel, and had a greater impact on the anode reaction process. The AC result in a negative shift to X80 free-corrosion potential and increased the free-corrosion current density. The AC accelerated the mass transfer process of ions, which is manifested by the decrease of the diffusion resistance under cathodic polarization. Also, the AC changed the development morphology of corrosion, with the corrosion morphology changed from uniform corrosion to pitting corrosion and finally localized corrosion. At high AC current density, a strong oxidant γ-FeOOH appears in the corrosion products, which accelerates the corrosion further. |
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