| YIN Ze-bin,ZHONG Xian-kang,HU Jun-ying.Effect of Local Calcium Carbonate Deposition on Corrosion Behavior of N80 Carbon Steel[J],50(10):337-344, 383 |
| Effect of Local Calcium Carbonate Deposition on Corrosion Behavior of N80 Carbon Steel |
| Received:May 25, 2021 Revised:September 02, 2021 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2021.10.035 |
| KeyWord:carbon steel scaling calcium carbonate local deposition electrochemical corrosion local corrosion |
| Author | Institution |
| YIN Ze-bin |
School of Petroleum and Natural Gas Engineering |
| ZHONG Xian-kang |
School of Petroleum and Natural Gas Engineering ;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu , China |
| HU Jun-ying |
School of Petroleum and Natural Gas Engineering ;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu , China |
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| Abstract: |
| This paper studied the effect of local calcium carbonate deposition on the corrosion behaviors of N80 carbon steel in order to provide new ideas for the petroleum industry to solve the corrosion problem caused by calcium carbonate deposition. The author adopted the constant potential cathodic polarization method to induce the calcium carbonate to deposit at the local position of the electrode. Electrochemical impedance spectroscopy (EIS) and wire beam electrode technology (WBE) were used to study the corrosion behavior of N80 carbon steel during local calcium carbonate deposition. The morphology and composition of corrosion (uniform, local, and galvanic corrosion) products were analyzed using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The electrochemical test results showed that the deposition of calcium carbonate would positively shift the corrosion potential of electrode by about 100 mV. Under the same conditions, the capacitive arc diameter of the electrode covered by CaCO3 deposit was much larger than that of the bare electrode. After the electrode was immersed for a longer time, the capacitive arc radius of the bare electrode became larger, while the capacitive arc of the electrode covered by CaCO3 deposit first increased and then decreased over time. The results of the galvanic electrode showed that the electrode covered by CaCO3 deposit acted as the cathode in the galvanic corrosion and the bare electrode was the anode. Polarity reverse did not occur during the 168 h immersion. The galvanic current density finally stabilized at –0.4 μA/cm2. The WBE results showed that the potential at the calcium carbonate deposition area at the beginning of the immersing was higher than other areas and all was cathode current. After 24 h immersion, the anode spots gradually appeared in the calcium carbonate deposition area. After 72 h immersion, the position with the most negative potential began to shift to the calcium carbonate deposition area. The morphology analysis showed that corrosion products on the surface of the electrode covered by CaCO3 deposit were complete and dense, providing a better protective effect for the carbon steel. Local corrosion pits were observed on the substrate after the removal of corrosion products. In summary, the locally deposited calcium carbonate shows protective effect on the electrode in a certain extent, but it will induce galvanic corrosion. As the immersion time becomes longer, the locally deposited calcium carbonate will cause local corrosion due to the presence of the oxygen concentration difference battery and the autocatalytic effect. |
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