鈍化液中的鋅對鍍鋅件鉻酸鹽鈍化的影響及鉻酸鹽鈍化液再生研究
發(fā)布時間：2018-11-18 06:27
【摘要】：鉻酸鹽鈍化是當前批量熱鍍鋅行業(yè)應(yīng)用最廣泛、性價比最高的處理方法之一,但是鉻酸鹽鈍化液具有高致癌性,且其在使用一段時候后,鈍化工件表面出現(xiàn)白色粉化物,影響了鍍件外觀,不得不定期更換鈍化液,不但增加了企業(yè)生產(chǎn)成本,同時對環(huán)境產(chǎn)生很大的危害。由于目前無鉻鈍化技術(shù)在批量熱鍍鋅行業(yè)的工業(yè)應(yīng)用條件尚不成熟,因此尋求有效延長鉻酸鹽鈍化液的使用壽命的方法,達到少排放甚至零排放,是熱鍍鋅行業(yè)密切關(guān)注且亟待解決的問題。初步研究發(fā)現(xiàn)出現(xiàn)粉化現(xiàn)象與溶液中的鋅離子濃度升高有關(guān),因此本文以鉻酸鹽鈍化液中的鋅為研究對象,研究了鋅對鉻酸鹽鈍化產(chǎn)生的影響及影響機理、鉻酸鹽鈍化液中的鋅含量的測定方法、鉻酸鹽鈍化液的再生。用SEM、EDS、XRD、XPS研究了鋅對鉻酸鹽鈍化膜形貌及成分的影響;用NSS、EIS、Tafel極化曲線測試研究了鋅對鉻酸鹽鈍化膜耐蝕性的影響。得出以下主要結(jié)論:1、研究發(fā)現(xiàn),鈍化液中鋅離子的存在,使鉻酸鹽鈍化膜上形成了較多的顆粒物,鋅含量越高膜層表面顆粒物越多。膜層上顆粒物的鋅氧比約為1:2。XRD分析發(fā)現(xiàn),鈍化液中鋅的存在并不改變鈍化膜的物質(zhì)種類,鈍化膜主要是以鋅、鉻化合物組成。XPS分析表明,隨著溶液中鋅離子含量增加,膜層O含量增加,Zn/Cr原子比上升,表明當鉻酸鹽鈍化液中存在含量較高的Zn時,鈍化膜中會形成較多的鋅氧化合物。NSS、EIS、Tafel均表明,鈍化液中鋅的存在有助于提高鉻酸鹽鈍化膜的耐蝕性。提出了鋅對鉻酸鹽鈍化產(chǎn)生影響的機理,認為鉻酸鹽鈍化液中的鋅會促進耐蝕性更好的膜層的形成。在空氣成膜階段,溶液中鋅離子參與反應(yīng)生成了顆粒物鑲嵌在膜層中,形成致密度有別于內(nèi)膜層的外膜層。2、開發(fā)了一種用EDTA滴定法測定鋅含量的方法:用陰離子樹脂交換除去鈍化液中的Cr(VI),用鉻黑T做指示劑,用EDTA二鈉滴定鋅含量。該滴定方法操作簡單、測試成本低、重現(xiàn)性好、滴定終點易于判斷,誤差可控制在5%以內(nèi),可用于鉻酸鹽鈍化液中含量在50~1400mg/L的鋅的測定。3、通過靜態(tài)吸附的方法,用732強酸性陽離子交換樹脂再生鉻酸鹽鈍化液,對交換時間、溶液p H值、樹脂用量、溶液初始濃度、樹脂再生性能進行了研究。該樹脂能夠選擇性的吸附除去鋅離子,但不會對鈍化液中Cr(VI)含量產(chǎn)生影響。紅外試驗證實732強酸性陽離子交換樹脂的吸附位置為磺酸基團(-SO3H),交換反應(yīng)不引入其他雜質(zhì)離子,且可下調(diào)鈍化液p H值。732強酸性陽離子交換樹脂的吸附速度快效率高,對Zn(II)的吸附符合單分子層吸附規(guī)律,具有飽和吸附性,飽和吸附量為85.6 mg/g。樹脂的吸附性能和脫附再生性能良好,可實現(xiàn)樹脂循環(huán)利用。該樹脂再生鉻酸鹽鈍化液的最佳p H為3~6。
[Abstract]:Chromate passivation is one of the most widely used and cost-effective treatment methods in batch galvanizing industry. However, chromate passivation solution has high carcinogenicity, and white powder appears on the surface of passivated workpiece after being used for a period of time. It not only increases the production cost, but also causes great harm to the environment because of the influence on the appearance of the plating parts and the need to replace the passivation solution regularly. Because the industrial application condition of chromium-free passivation technology in batch hot dip galvanizing industry is not mature at present, the method of effectively prolonging the service life of chromate passivation solution is sought, and the discharge is less or even zero. It is a hot-dip galvanizing industry to pay close attention to and urgent problems to be solved. It is found that the phenomenon of pulverization is related to the increase of zinc ion concentration in the solution. Therefore, the effect of zinc on chromate passivation and its mechanism are studied in this paper. Determination of zinc content in chromate passivation solution, regeneration of chromate passivation solution. The effect of zinc on the morphology and composition of chromate passivation film was studied by SEM,EDS,XRD,XPS and the corrosion resistance of chromate passivation film was studied by NSS,EIS,Tafel polarization curve. The main conclusions are as follows: 1. It is found that the existence of zinc ions in the passivation solution results in the formation of more particles on the chromate passivation film, and the higher the zinc content, the more particles on the surface of the film. The zinc-oxygen ratio of particles on the film was about 1:2.XRD analysis. It was found that the existence of zinc in the passivation solution did not change the species of the passivation film, and the passivation film was mainly composed of zinc and chromium compounds. XPS analysis showed that the passivation film was composed of zinc and chromium compounds. With the increase of zinc ion content in the solution, the O content of the film increases, and the Zn/Cr atom ratio increases, which indicates that more zinc and oxygen compounds will be formed in the passivation film when the content of Zn in chromate passivation solution is higher. The existence of zinc in passivation solution can improve the corrosion resistance of chromate passivation film. The mechanism of the effect of zinc on chromate passivation is put forward. It is considered that zinc in chromate passivation solution can promote the formation of better corrosion resistant film. At the stage of air film formation, zinc ions in solution take part in the reaction to form particles embedded in the film layer, forming an outer layer with density different from that of the inner membrane. A method for the determination of zinc by EDTA titration was developed. The content of zinc was titrated with EDTA disodium and chromium black T was used as indicator for the removal of Cr (VI), from passivating solution by anion resin exchange. The titration method is simple in operation, low in cost, good in reproducibility, easy to judge the end point of titration, and the error can be controlled within 5%. It can be used for the determination of zinc in chromate passivation solution in 50~1400mg/L. The chromate passivation solution was regenerated by 732 strong acid cation exchange resin. The exchange time, pH value of the solution, the amount of resin, the initial concentration of the solution and the regeneration performance of the resin were studied. The resin can selectively adsorb and remove zinc ion, but it has no effect on Cr (VI) content in passivation solution. The adsorption position of 732 strong acid cation exchange resin is sulfonic group (- SO3H), and no other impurity ions are introduced into the exchange reaction. The pH value of passivating solution can be down-regulated. The adsorption rate of 732 strong acid cation exchange resin is fast and high efficiency. The adsorption of Zn (II) conforms to the law of monolayer adsorption, and has saturated adsorption capacity of 85.6 mg/g.. The resin has good adsorption and desorption and regeneration properties and can be recycled. The optimum pH of chromate passivating solution regenerated by this resin is 3o 6.
【學位授予單位】：華南理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TG174.4
本文編號：2339146
[Abstract]:Chromate passivation is one of the most widely used and cost-effective treatment methods in batch galvanizing industry. However, chromate passivation solution has high carcinogenicity, and white powder appears on the surface of passivated workpiece after being used for a period of time. It not only increases the production cost, but also causes great harm to the environment because of the influence on the appearance of the plating parts and the need to replace the passivation solution regularly. Because the industrial application condition of chromium-free passivation technology in batch hot dip galvanizing industry is not mature at present, the method of effectively prolonging the service life of chromate passivation solution is sought, and the discharge is less or even zero. It is a hot-dip galvanizing industry to pay close attention to and urgent problems to be solved. It is found that the phenomenon of pulverization is related to the increase of zinc ion concentration in the solution. Therefore, the effect of zinc on chromate passivation and its mechanism are studied in this paper. Determination of zinc content in chromate passivation solution, regeneration of chromate passivation solution. The effect of zinc on the morphology and composition of chromate passivation film was studied by SEM,EDS,XRD,XPS and the corrosion resistance of chromate passivation film was studied by NSS,EIS,Tafel polarization curve. The main conclusions are as follows: 1. It is found that the existence of zinc ions in the passivation solution results in the formation of more particles on the chromate passivation film, and the higher the zinc content, the more particles on the surface of the film. The zinc-oxygen ratio of particles on the film was about 1:2.XRD analysis. It was found that the existence of zinc in the passivation solution did not change the species of the passivation film, and the passivation film was mainly composed of zinc and chromium compounds. XPS analysis showed that the passivation film was composed of zinc and chromium compounds. With the increase of zinc ion content in the solution, the O content of the film increases, and the Zn/Cr atom ratio increases, which indicates that more zinc and oxygen compounds will be formed in the passivation film when the content of Zn in chromate passivation solution is higher. The existence of zinc in passivation solution can improve the corrosion resistance of chromate passivation film. The mechanism of the effect of zinc on chromate passivation is put forward. It is considered that zinc in chromate passivation solution can promote the formation of better corrosion resistant film. At the stage of air film formation, zinc ions in solution take part in the reaction to form particles embedded in the film layer, forming an outer layer with density different from that of the inner membrane. A method for the determination of zinc by EDTA titration was developed. The content of zinc was titrated with EDTA disodium and chromium black T was used as indicator for the removal of Cr (VI), from passivating solution by anion resin exchange. The titration method is simple in operation, low in cost, good in reproducibility, easy to judge the end point of titration, and the error can be controlled within 5%. It can be used for the determination of zinc in chromate passivation solution in 50~1400mg/L. The chromate passivation solution was regenerated by 732 strong acid cation exchange resin. The exchange time, pH value of the solution, the amount of resin, the initial concentration of the solution and the regeneration performance of the resin were studied. The resin can selectively adsorb and remove zinc ion, but it has no effect on Cr (VI) content in passivation solution. The adsorption position of 732 strong acid cation exchange resin is sulfonic group (- SO3H), and no other impurity ions are introduced into the exchange reaction. The pH value of passivating solution can be down-regulated. The adsorption rate of 732 strong acid cation exchange resin is fast and high efficiency. The adsorption of Zn (II) conforms to the law of monolayer adsorption, and has saturated adsorption capacity of 85.6 mg/g.. The resin has good adsorption and desorption and regeneration properties and can be recycled. The optimum pH of chromate passivating solution regenerated by this resin is 3o 6.
【學位授予單位】：華南理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TG174.4
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