發(fā)布時間：2018-05-09 09:14

  本文選題：Q235碳鋼 + 304不銹鋼��； 參考：《北京化工大學》2015年碩士論文

【摘要】：由于混凝土的碳化作用和環(huán)境中氯離子的侵蝕均能導致鋼筋銹蝕,采用不銹鋼代替碳素鋼可以有效延長混凝土結(jié)構(gòu)的使用期限。因此研究和對比不同鋼筋在混凝土孔隙液中的耐蝕性能對鋼筋混凝土結(jié)構(gòu)的應(yīng)用有著十分重要的意義。本文通過動電位極化,恒電位極化,Mott-Schottky曲線,EIS等電化學技術(shù)以及XPS、掃描電鏡觀察等方法對Q235碳鋼和304不銹鋼(304 SS)兩種材料在五種不同的模擬孔隙液中的耐蝕性進行了對比研究；對兩種碳化混凝土模擬孔隙液中Cl-對碳鋼亞穩(wěn)態(tài)孔蝕的特征參數(shù)的影響進行了深入的分析;并對碳鋼表面亞穩(wěn)態(tài)孔蝕向穩(wěn)態(tài)孔蝕的轉(zhuǎn)化進行了探討。所得到的主要結(jié)論如下：(1)對五種不同pH值的模擬孔隙液中無氯以及有氯離子兩種情況下Q235碳鋼和304 SS的耐腐蝕性能進行對比。無氯條件下,兩種鋼材在五種pH值的孔隙液中均能保持很好的鈍化狀態(tài),耐蝕性能無明顯差別;加入0.05 mol/L Cl-后304 SS的耐蝕性仍然沒有變化,而Q235碳鋼僅在pH 13.3的孔隙液中能維持很好的鈍化性能,但在輕微碳化(pH 11.5)和碳化(pH 10.3和9.7)的模擬孔隙液中耐蝕性能顯著下降,極化曲線上產(chǎn)生明顯的亞穩(wěn)態(tài)電流波動并發(fā)生了小孔腐蝕。Mott-Schottky曲線測試結(jié)果顯示,304 SS表面鈍化膜中的摻雜濃度隨著溶液pH值的降低略有上升,有氯和無氯條件下相差不大;Q235碳鋼在無氯條件下鈍化膜的摻雜濃度隨pH值的變化不明顯,有氯時鈍化膜摻雜濃度隨溶液pH值的降低有較大提升,導致耐蝕性下降。XPS結(jié)果表明：無氯離子條件下Q235碳鋼表面膜層中Fe3+/Fe2+隨pH值下降無明顯變化,而在有氯離子的孔隙液中Fe3+/Fe2+隨pH值下降明顯降低,表明鈍化膜的穩(wěn)定性下降；不同pH的模擬孔隙液中304SS的鈍化膜成分變化不明顯,因而其耐蝕性也無明顯變化。(2)兩種碳化模擬孔隙液(pH 10.3和9.7)中隨著Cl-濃度的增大,Q235碳鋼的亞穩(wěn)態(tài)孔蝕電位Em和穩(wěn)定孔蝕電位Eb值均負移,其中Eb與ln[Cl-]成線性關(guān)系：Em和Eb均隨著溶液中l(wèi)n[Cl-]/[OH]和1nCagg/Cinh(侵蝕性離子與緩蝕性離子之比,[Cl*]/[OH-][HCO3][CO32-])的增加而下降,也呈良好的線性關(guān)系。Cl-濃度增加,碳鋼表面鈍化膜中的施主濃度Nd和平帶電位Efb均增大,膜中的空位增多,鈍化膜電阻下降,電容升高,膜層的致密性下降,碳鋼的孔蝕敏感性增加。(3)隨著Cl-濃度的增大,Q235碳鋼的亞穩(wěn)態(tài)小孔形核數(shù)目增加、形核率最大值對應(yīng)電位負移、小孔平均壽命增加、理論亞穩(wěn)孔半徑增大,因此Cl-對亞穩(wěn)態(tài)孔蝕的形核和生長均起到促進作用。亞穩(wěn)態(tài)小孔半徑的最大值出現(xiàn)的電位與亞穩(wěn)孔形核率最大值出現(xiàn)的電位相一致,該電位略低于穩(wěn)定孔蝕電位Eb,說明亞穩(wěn)小孔半徑越大、小孔數(shù)量越多,轉(zhuǎn)化為穩(wěn)定孔的幾率越大,大量的小孔集中爆發(fā)后會很快轉(zhuǎn)入穩(wěn)定孔蝕階段。(4)Q235碳鋼在略高于Em的電位進行恒電位極化,形成的亞穩(wěn)態(tài)小孔的孔徑較小(小于1μm),孔口多呈開放狀態(tài)。極化電位升高到鈍化區(qū)中段(高于Em,但遠低于Eb),形成的亞穩(wěn)態(tài)小孔的尺寸增大(1μm左右);多個亞穩(wěn)態(tài)小孔有聚集形核、生長的趨勢,蝕孔底部可以觀察到有小孔向下生長的痕跡；部分孔口尚存未完全破裂的鈍化膜,由電流波動峰積分計算證實亞穩(wěn)態(tài)小孔在膜下繼續(xù)深挖發(fā)展。極化電位接近Eb時,碳鋼表面發(fā)生幾百微米的穩(wěn)定蝕孔群,蝕孔群由許多集中生長的小孔組成,許多小孔較深,表面多有腐蝕產(chǎn)物覆蓋；腐蝕產(chǎn)物膜中有氯離子富集,與基體接觸誘發(fā)大量孔蝕形核,即亞穩(wěn)態(tài)孔蝕主要在穩(wěn)定孔的周圍形核與生長,導致了穩(wěn)定蝕孔在試樣表面的橫向生長。
[Abstract]:As the carbonization of concrete and the erosion of chloride ions in the environment can cause corrosion of steel, the use of stainless steel instead of carbon steel can effectively prolong the use period of concrete structures. Therefore, it is of great significance to study and compare the corrosion resistance of different reinforcing bars in the pore fluid of concrete. In this paper, the corrosion resistance of two kinds of Q235 carbon steel and 304 stainless steel (304 SS) materials in five different simulated pore fluids were studied by means of dynamic potential polarization, constant potential polarization, Mott-Schottky curve, EIS and other electrochemical techniques, XPS and scanning electron microscopy, and Cl- to carbon steel in two carbonated concrete pore fluid. The influence of the characteristic parameters of steady-state pore erosion was deeply analyzed, and the transformation of metastable pore erosion to steady-state pore erosion of carbon steel surface was discussed. The main conclusions are as follows: (1) the comparison of corrosion resistance of Q235 carbon steel and 304 SS under two different pH values of simulated pore fluid and two kinds of chloride ions Under the condition of chlorine free, two kinds of steel can keep a very good passivation state in the five pH value pores, and there is no obvious difference in corrosion resistance. The corrosion resistance of 304 SS after adding 0.05 mol/L Cl- remains unchanged, and Q235 carbon steel can maintain very good passivation properties in the pore solution of pH 13.3, but in mild carbonization (pH 11.5) and carbonization (pH 10.3, and 10.3) 9.7) the corrosion resistance in the simulated pore fluid decreased significantly. The apparent metastable current fluctuation on the polarization curve and the small hole corrosion.Mott-Schottky curve showed that the doping concentration in the passivation film on the 304 SS surface slightly increased with the decrease of the pH value of the solution, and the difference between the chlorine and the chlorine free conditions was not significant; Q235 carbon steel was no chlorine. The doping concentration of passivating film is not obvious with the change of pH value. The doping concentration of passivating film increases with the decrease of pH value, which leads to the decrease of corrosion resistance.XPS. The result shows that the Fe3+/Fe2+ in the surface film layer of Q235 carbon steel film decreases with the decrease of pH value under the condition of chlorine free ion, and Fe3+/Fe2+ in the pore solution with chlorine ion is followed by Fe3+/Fe2+ The decrease of pH value indicates a decrease in the stability of the passivation film, and there is no obvious change in the passivation film composition of the 304SS in the simulated pore fluid of different pH. (2) the metastable potential Em of Q235 carbon steel and the stable orifice potential Eb in the two simulated pore fluid (pH 10.3 and 9.7) with the increase of Cl- concentration Both Eb and ln[Cl-] have a linear relationship. Both Em and Eb decrease with the increase of ln[Cl-]/[OH] and 1nCagg/Cinh in the solution (the ratio of erosive ions to corrosion ions, [Cl*]/[OH-][HCO3][CO32-]), and a good linear relationship between the concentration of.Cl- and the increase of the concentration Nd and potential Efb in the passivation film on the surface of carbon steel. The number of vacancies in the film increases, the resistance of the passivation film decreases, the capacitance increases, the density of the film decreases, and the porosity of carbon steel increases. (3) as the concentration of Cl- increases, the number of metastable small pores in the Q235 carbon steel increases, the maximum value of the nucleation rate corresponds to the negative shift of the potential, the average life span of the pores increases, and the radius of the theoretical metastable hole increases, thus Cl- is substable to metastable metastabilities. The nucleation and growth of the orifice are all promoted. The potential of the maximum value of the metastable pore radius coincides with the potential of the maximum value of the metastable pore nucleation rate. The potential is slightly lower than the stable orifice potential Eb. It shows that the larger the radius of the metastable pore is, the more the number of small pores is, the greater the probability of transforming into a stable hole, and a large number of small holes concentrated. It will soon turn into the stable pore erosion stage. (4) the Q235 carbon steel has a constant potential polarization of slightly higher than the potential of Em, the pore size of the metastable small hole is smaller (less than 1 m), and the pore opening is more open. The polarization potential rises to the middle part of the passivation region (higher than Em, but far below Eb), and the size of the metastable small hole is increased (about 1 mu m), and a number of metastable metastabilities. At the bottom of the orifice, there is a trace of downward growth of small holes, and there is a passivating film that has not been completely broken at the bottom of the orifice. It is confirmed that the metastable small hole continues to develop under the membrane by the current wave peak integral calculation. The stable etch group of several hundred microns on the surface of carbon steel occurs when the polarization potential is close to Eb. The orifice group is composed of many small pores which are concentrated. Many small holes are deep and the surface is covered with corrosion products. The chloride ion is enriched in the corrosion product membrane, and a large number of orifice nucleation is induced by contact with the matrix. That is, the metastable pore erosion mainly nucleates and grows around the stable hole, leading to the lateral growth of the stable etch on the surface of the specimen.

【學位授予單位】：北京化工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TU528

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本文編號：1865441