Combined effect of hydrostatic pressure and dissolved oxygen on the electrochemical behavior of low-alloy high-strength steel
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摘要: 采用動電位極化測試和掃描電子顯微鏡/能譜儀表征, 通過理想動電位極化曲線分析方法和微觀腐蝕形貌觀察研究了靜水壓與溶解氧耦合作用對低合金高強鋼在質量分數為3.5% NaCl溶液中腐蝕電化學行為的影響. 結果表明: 隨著靜水壓和溶解氧溶度的同時增大, 腐蝕電位先增高而后逐漸降低, 腐蝕電流呈非線性增長; 靜水壓與溶解氧在腐蝕過程中存在相互競爭抑制關系, 在靜水壓與溶解氧同時增長過程中, 溶解氧首先促進陰極反應過程并抑制陽極反應過程, 而后靜水壓逐漸加速陽極過程并對陰極反應過程有一定的抑制作用; 靜水壓與溶解氧耦合作用加速了腐蝕產物膜的生長, 增加了低合金高強鋼表面點蝕坑的數量和生長尺寸.Abstract: With the development of marine industry, the performances of metal materials in marine environment have gathered much attention of scientists. Seawater, as a Cl--containing electrolyte, degrades the properties of steel structures and limits their service life due to its erosion to steel surface. The corrosion phenomena of low-alloy high-strength steels in surface seawater are well known but not sufficiently understood in deep-sea environment. The effect of hydrostatic pressure on the corrosion behavior of low-alloy steels is a focus in this aspect. However, the results from the laboratory study cannot well illustrate the ones from the field test, because some factors change simultaneously with the increase of ocean depth. Therefore, it is necessary to study the corrosion behaviors of steels in a multi-factor coupled environment. In this report, the combined effect of hydrostatic pressure and dissolved oxygen on the electrochemical behavior of low-alloy high-strength steel in 3.5% (mass fraction) NaCl solution was investigated using potentiodynamic polarization tests and scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) measurements. The results show that the corrosion potential increases at first and then decreases with the increase of both hydrostatic pressure and dissolved oxygen. The corrosion current density exhibits a nonlinear increasing tendency with the increase of these two factors. The ideal polarization curve method was used to analyze the interaction of hydrostatic pressure and dissolved oxygen in the corrosion process. The results indicate that there is a competitive inhibition relationship between hydrostatic pressure and dissolved oxygen. With the increase of both hydrostatic pressure and dissolved oxygen, dissolved oxygen first accelerates the cathodic reaction process and inhibits the anodic reaction process. Afterwards, hydrostatic pressure starts accelerating the anodic reaction rate and inhibits the acceleration of the cathodic process caused by dissolved oxygen. The corrosion films on the steel surface significantly inhibit the acceleration to corrosion process given by the combined effect of hydrostatic pressure and dissolved oxygen. Moreover, these two combined factors encourage the growth of corrosion films and increase the number and sizes of corrosion pits forming on the steel surface.
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圖 3 低合金高強鋼在不同靜水壓與溶解氧環境下浸泡0.5 h后的動電位極化曲線
Figure 3. Potentiodynamic polarization curves of low-alloy high-strength steel with different hydrostatic pressures and dissolved oxygen levels after 0.5 h pre-immersion
圖 4 利用理想的極化曲線法分析低合金高強鋼在不同靜水壓和溶解氧條件下的動電位極化曲線示意圖
Figure 4. Supposed diagram of ideal polarization curves of low-alloy high-strength steel with different hydrostatic pressures and dissolved oxygen levels
圖 5 低合金高強鋼在不同靜水壓與溶解氧環境下浸泡24 h后的動電位極化曲線
Figure 5. Potentiodynamic polarization curves of steel specimens after 24 h pre-immersion with different hydrostatic pressures and dissolved oxygen levels in 3.5% NaCl solution
圖 6 試樣分別浸泡0.5 h和24 h后的腐蝕電流密度隨靜水壓與溶解氧的變化曲線
Figure 6. Corrosion current density of steel specimens with different hydrostatic pressures and dissolved oxygen levels for 0.5 h and 24 h immersion
圖 7 低合金高強鋼分別在30 ATO和1 ATO條件下浸泡24 h后的微觀形貌. (a) 30 ATO; (b) 1 ATO
Figure 7. SEM images of corrosion morphologies of low-alloy high-strength steel at 30 ATO and 1 ATO after 24 h immersion: (a) 30 ATO; (b) 1 ATO
圖 8 低合金高強鋼分別在30 ATO和1 ATO條件下浸泡96 h后的微觀形貌及相應位置能譜圖. (a) 30 ATO; (b) 1 ATO; (c) 位置1的能譜圖; (d) 位置3的能譜圖; (e) 位置2的能譜圖; (f) 位置4的能譜圖
Figure 8. SEM images and EDS of corrosion morphologies of low-alloy high-strength steel at 30 ATO and 1 ATO after 96 h immersion: (a) 30 ATO; (b) 1 ATO; (c) EDS results of position 1; (d) EDS results of position 3; (e) EDS results of position 2; (f) EDS results of position 4
圖 9 低合金高強鋼在30 ATO和1 ATO條件下浸泡192 h后去除腐蝕產物后的掃描電鏡形貌. (a) 30 ATO; (b) 1 ATO
Figure 9. SEM images of corrosion morphologies of low-alloy high-strength steel without corrosion products at 30 ATO and 1 ATO after 96 h immersion: (a) 30 ATO; (b) 1 ATO
表 1 低合金高強鋼的化學組分(質量分數)
Table 1. Chemical composition of the studied low-alloy high-strength steel ?
% C Si Mn Cr Ni Mo V Fe 0.1 0.29 0.57 0.6 4.96 0.6 0.09 余量 
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中文字幕在线观看表 2 利用Tafel外擴法得到的低合金高強鋼動電位極化曲線參數
Table 2. Electrochemical corrosion parameters obtained using Tafel extrapolation method
時間/h 測試環境 Ecorr/V(vs Ag/AgCl) icorr/(μA·cm-2) Va/mV Vc/mV 0.5 1 ATO -0.60247 6.13 61.299 -146.9 10 ATO -0.36904 29.49 56.228 -172.01 30 ATO -0.38763 36.81 59.153 -215.52 60 ATO -0.46487 39.05 60.089 -172.71 24 1 ATO -0.52252 2.43 64.909 -100.4 10 ATO -0.47004 4.90 50.241 -105.5 30 ATO -0.49089 5.29 62.074 -116.1 60 ATO -0.51105 5.38 67.626 -111.32
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