【摘要】：工業(yè)窯爐的省煤器在工業(yè)生產(chǎn)中經(jīng)常會(huì)遇到露點(diǎn)腐蝕問(wèn)題。由于工業(yè)燃料中含有S、C、N等元素,煙氣中通常含有相應(yīng)的氧化物,這些氧化物會(huì)與煙氣中的水蒸氣反應(yīng)生成酸性蒸汽。當(dāng)酸性蒸汽遇到低于露點(diǎn)溫度的省煤器外壁時(shí),就會(huì)凝結(jié)成酸性液滴,使省煤器外壁產(chǎn)生劇烈腐蝕,導(dǎo)致使用壽命縮短。所以防止露點(diǎn)腐蝕是提高省煤器使用壽命的關(guān)鍵。工業(yè)上常用碳鋼作為省煤器材料,所以本文以Q235碳鋼作為基材,在其表面通過(guò)化學(xué)鍍技術(shù)鍍覆一層Ni-Cu-P鍍層,提高其耐蝕性。利用兩步法制備性能更好的鍍層,提高鍍層對(duì)基體起保護(hù)作用的時(shí)間,并對(duì)鍍層的腐蝕機(jī)理進(jìn)行研究。本文通過(guò)正交試驗(yàn)確定較佳的化學(xué)鍍配方和工藝條件,通過(guò)SEM對(duì)鍍層表面形貌進(jìn)行觀察,通過(guò)EDS鍍層表面元素含量進(jìn)行分析,采用XRD和XPS分析了鍍層的結(jié)構(gòu)和表面元素。通過(guò)孔隙率測(cè)試、硬度測(cè)試、接觸角測(cè)試等測(cè)試方法研究了施鍍時(shí)間對(duì)鍍層各種性能的影響。利用腐蝕浸泡實(shí)驗(yàn)和動(dòng)電位極化曲線對(duì)鍍層在80℃C的模擬煙氣冷凝液、5%H2SO4、10%H2SO4和20%H2SO4溶液中的腐蝕行為進(jìn)行了研究。主要研究結(jié)果如下:本實(shí)驗(yàn)所用的化學(xué)鍍配方及工藝條件為:NiSO4 25g/L、CuSO40.9g/L、NaH2PO235g/L、Na3C6H5O745g/L、NaCH3COO 15g/L 和硫脲 1mg/L,溫度為84℃,鍍液pH值為6,施鍍時(shí)間1.5h。所得鍍層中,Ni、Cu和P元素含量分別78.72%、7.56%和13.72%,Cu和P與Ni形成固溶體,使得鍍層為非晶體結(jié)構(gòu),其中P和部分Ni之間交換電子形成共價(jià)鍵,而Cu是以單質(zhì)形式存在。在Q235碳鋼表面化學(xué)鍍Ni-Cu-P (Ni-Cu-P/Q235)能顯著提高Q235碳鋼在80℃的模擬煙氣冷凝液、5% H2SO4、10% H2SO4和20% H2SO4溶液中的耐蝕性,在上述四種介質(zhì)中,Ni-Cu-P/Q235的腐蝕速率是分別是Q235碳鋼的1/9、1/166、1/165和1/466;耐蝕性也優(yōu)于ND鋼,腐蝕速率分別是為ND鋼的1/6、1/136、1/139和1/351;在80℃三種濃度的H2SO4溶液中(5%、10%和20%),腐蝕速率分別是316L不銹鋼的1/8、1/10和1/121,耐蝕性也優(yōu)于316L不銹鋼。利用兩步法制備四種鍍層,其中一級(jí)施鍍時(shí)間為1.5h不變,二級(jí)施鍍時(shí)間分別為0.25h、0.5h、1 h和1.5h,鍍液成分和條件同前。兩步法能有效延長(zhǎng)鍍層對(duì)基體的保護(hù)時(shí)間。當(dāng)二級(jí)鍍層施鍍1.5 h時(shí)鍍層的性能最好,厚度為43.8 μm,孔隙率接近0,鍍層硬度最小(656.1 Hv),在80℃的5%H2SO4溶液中的腐蝕速率最低,鍍層發(fā)生鼓泡的時(shí)間(418h)是一步制備的鍍層鼓泡時(shí)間(106h)的3.9倍。當(dāng)二級(jí)施鍍時(shí)間為1.5 h時(shí),鍍層在80℃的5%H2SO4溶液中浸泡過(guò)程中,鍍層先后經(jīng)歷一個(gè)由米黃色變?yōu)楹谏⑷缓蠹t色、最后為黑色的過(guò)程。米黃色為鍍層的初始顏色。變?yōu)楹谏且驗(yàn)樵诮葸^(guò)程中,鍍層表面Ni選擇性溶解所致;當(dāng)鍍層表面Ni繼續(xù)溶解導(dǎo)致Cu富集后鍍層變紅色;當(dāng)二級(jí)鍍層完全腐蝕掉,一級(jí)鍍層的Ni開始溶解時(shí)鍍層又變成黑色。在一級(jí)鍍層腐蝕掉之前,鍍層的腐蝕速率變化平緩,鍍層對(duì)基體仍起到保護(hù)作用。
[Abstract]:The economizer of industrial kiln often meets the problem of dew point corrosion in industrial production. Since industrial fuels contain elements such as Schion N and so on, the flue gas usually contains corresponding oxides, which react with the water vapor in the flue gas to form acid steam. When acid steam encounters the outside wall of economizer which is lower than dew point temperature, it will condense into acid droplets, which will cause severe corrosion on the outside wall of economizer and shorten the service life. So to prevent dew-point corrosion is the key to improve the service life of economizer. Carbon steel is commonly used as economizer material in industry. Therefore, Q235 carbon steel is used as substrate in this paper. The surface of Q235 carbon steel is coated with a layer of Ni-Cu-P coating by electroless plating technology to improve the corrosion resistance of Q235 carbon steel. The coating with better performance was prepared by two-step method to improve the protective time of the coating on the substrate and the corrosion mechanism of the coating was studied. In this paper, the optimum formula and technological conditions of electroless plating were determined by orthogonal test. The surface morphology of the coating was observed by SEM, the surface element content of EDS coating was analyzed, and the structure and surface elements of the coating were analyzed by XRD and XPS. The effect of plating time on the properties of the coating was studied by means of porosity test, hardness test and contact angle test. Corrosion behavior of the coating in simulated flue gas condensate at 80 鈩，

本文編號(hào)：2165235