不锈钢表面导电聚苯胺薄膜的耐腐蚀性能
试验研究
不锈钢表面导电聚苯胺薄膜的耐腐蚀性能
白春钰,梁燕萍
(西安电子科技大学应用化学系,陕西西安 710071)
[摘 要] 导电聚苯胺性能优异,应用前景广阔。采用原位聚合法在不锈钢表面制备了绿色导电聚苯胺(P An )薄膜,研究了苯胺(An )与硫酸的物质的量浓度比、苯胺(An )与过硫酸铵(APS )的物质的量浓度比以及
反应温度对合成的影响。用点滴试验、阳极极化曲线评价了聚苯胺薄膜的耐腐蚀性能。通过正交试验确定了本试验条件下的最优工艺条件为:c (An )∶c (H 2S O 4)=1∶3,c (An )∶c (APS )=1∶1,反应温度为18℃;通过阳极极化曲线测试发现,在最优工艺条件下制备的覆盖了聚苯胺薄膜的不锈钢试片在3.5%NaCl 溶液中点腐蚀电位正移了1000mV 左右。说明该聚苯胺薄膜具有较好的耐腐蚀性能。
[关键词] 导电聚苯胺薄膜;耐蚀性;不锈钢
[中图分类号]TG174.46 [文献标识码]A [文章编号]1001-1560(2008)07-0001-03
[收稿日期] 20080222
0 前 言
在导电聚合物中,聚苯胺由于其单体价格低廉、制备方法简单、导电性能良好、掺杂机理独特、稳定性良好等优点而备受关注,它是一种最有发展前景的导电聚合物。自从1985年用电化学方法在不锈钢表面合成了导电聚苯胺防腐蚀膜以后,聚苯胺作为一种新的防腐蚀材料才逐渐被引起重视,各国许多学者相继开始了这方面的研究,并取得了一系列重要的成果
[1]
。
目前,在金属表面制备导电聚苯胺膜的方法主要有2种:电化学法和化学法。电化学法简单易行,但不适用于大型工业化生产;化学法合成过程比较复杂,且由于聚苯胺分子链的强刚性和分子链间的强相互作用使其溶解性差,需要使用大量挥发性有机溶剂,对环境造成污染。最近研究的原位聚合沉积技术
[2,3]
,具有不需要
特殊设备、操作简单、膜厚可控、可涂布于各种形状的表面等优点,尤其对找不到合适溶剂的导电聚合物和某些特殊表面具有优势。用此方法在玻璃[4,5]
、纤维织
物
[6]
、高聚物
[7]
等的表面合成聚苯胺膜已有很多研究
报道,但在金属表面合成聚苯胺膜还未见报道。原则上,几乎任何基体的表面都可以通过原位聚合涂覆聚
苯胺膜
[8]
。基于此,本工作用原位聚合的方法在不锈
钢表面合成了导电聚苯胺薄膜,避免了因采用普通化学方法而使用大量挥发性有机溶剂(如某些酮类),同时研究了它的耐腐蚀性能。
1 试 验
1.1 试样及前处理
不锈钢试样尺寸为5.0mm ×2.0mm ×0.5mm ,并作如下处理:碱洗除油→水洗→化学抛光→4%Na 2CO 3中和→热水洗→冷水洗→自然晾干→待用。1.2 聚苯胺膜制备
分别配制50mL 0.3mol/L 的苯胺(An )硫酸溶液和等体积不同浓度的过硫酸铵(APS )溶液,然后将二者混合,放入待用的试片在不同温度下搅拌至基片膜变绿色,取出试片,用蒸馏水冲洗,100℃烘干,即制得耐蚀性聚苯胺薄膜。1.3 性能测定1.3.1 点滴试验
在室温下将10%HCl 点滴在试片表面,记录产生锈斑的时间,以此时间衡量聚苯胺膜的耐腐蚀性能。每个试样作3次点滴试验,计算平均时间。
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1.3.2 阳极极化曲线
以工作电极(不锈钢试片)、辅助电极(铂电极)、参比电极(饱和甘汞电极)构成三电极测量体系。工作电极用石蜡封装,留下4mm×4mm的工作面。腐蚀介质为3.5%NaCl溶液。测量系统由计算机与电极钝化曲线测试仪(西安电子科技大学化学系研制)组成,记录阳极电压与腐蚀电流的变化曲线。
2 结果与讨论
选定0.3mol/L苯胺,通过改变反应温度、苯胺与氧化剂的浓度比、苯胺与硫酸的浓度比,反应至基片膜变绿色。
2.1 反应温度的影响
由于反应温度对反应体系和所得产物的结构可能产生某种程度的影响,进而影响产物的性能,所以有必要研究苯胺聚合时反应温度的影响。苯胺在一定的温度范围内可以发生聚合,聚合温度低时,反应速度太慢,聚合温度过高时,反应速度过快。据此,按上述的制备方法,改变反应温度,考察聚苯胺膜耐蚀性的变化。试验结果见表1。
表1 反应温度的影响
温度/℃101826304050
点滴时间/m in20272516--
注:c(An)∶c(H
2
S O4)=1∶3, c(An)∶c(APS)=1∶1。
由表1可见,聚合反应对温度是比较敏感的,温度在30℃以下时,可以在试片表面形成具有耐蚀性的聚苯胺薄膜,30℃以上则成膜困难。这可能是由于随着反应温度的升高,反应速度加快,构成薄膜的颗粒尺寸逐渐变大,温度过高,快速成长的聚苯胺大颗粒难以吸附在基体表面形成薄膜所致。
2.2 苯胺与硫酸浓度比的影响
质子酸在苯胺的聚合过程中的作用主要是提供质子,满足聚合反应所需要的pH值,并以掺杂剂的形式进入聚苯胺骨架赋予聚苯胺导电性,因此可以在多种酸性介质中进行。本工作采用硫酸作为掺杂剂,在苯胺与硫酸的物质的量浓度比在1∶(1～5)范围内做点滴试验,用精密试纸检测聚合溶液的pH<2。试验结果见表2。
表2苯胺与硫酸浓度比的影响
c(An)∶c(H2S O4)1∶11∶21∶31∶41∶5
点滴时间/m in1923271412
注:c(An)∶c(APS)=1∶1,温度18℃。
由表2可见,随着硫酸浓度的增加,聚苯胺膜的耐蚀性先增加后减小,当增加到苯胺浓度的4倍以上,耐蚀性下降。这可能是由于随着硫酸浓度的增加,使反应速度加快,聚苯胺的粒径有所增长,膜的厚度随之增加,致密性和连续性都较好;但是当酸的浓度过高时,大粒径的聚苯胺颗粒短时间内产生,影响了薄膜的进一步形成,反而使膜变薄,致密性和连续性都下降,导致耐蚀性反而下降。
2.3 苯胺与过硫酸铵浓度比的影响
苯胺的氧化聚合电位较低,约为0.7V(vs SCE),因此在此之上的很多氧化剂均可用于引发苯胺的聚合,常用的有过硫酸铵、三氯化铁和重铬酸钾等。过硫酸铵由于氧化能力强,后处理简单,在-5～50℃内有很高的氧化活性而成为苯胺聚合中最常用的氧化剂。所以本工作采用过硫酸铵作为氧化剂来研究过硫酸铵浓度变化对苯胺聚合及耐蚀性的影响。试验结果见表3。
表3 苯胺与过硫酸铵浓度比的影响
c(An)∶c(APS) 1.0∶0.5 1.0∶1.0 1.0∶2.0 1.0∶3.0
点滴时间/m in23272513
注:c(An)∶c(H
2
S O4)=1∶3,温度18℃。
在试验中,氧化剂用量过小,苯胺得不到良好的聚合;氧化剂用量过大,反应速度过快,短时间内有大量聚苯胺沉淀生成,无法形成均匀性和稳定性良好的薄膜。由表3可见,当苯胺与过硫酸铵的浓度比不超过1.0∶3.0时,薄膜具有较好的耐蚀性,当苯胺与过硫酸铵的浓度比为1.0∶1.0时耐蚀性最好。
2.4 正交试验设计优选结果
为了进一步获得苯胺聚合反应的最佳工艺条件,同时考察综合因素的影响,采用正交试验对各聚合条件进行优化,对各单因素取3水平做正交试验,因素水平见表4。
表4 正交试验因素水平表
因素
A B C
c(An)∶c(H2S O4)c(An)∶c(APS)掺杂温度/℃水平11∶1 1.0∶0.510
水平21∶2 1.0∶1.018
水平31∶3 1.0∶2.026根据表4,不考虑3个因素之间的交互作用,采用L9(34)正交表进行试验,结果见表5。
表5 正交试验结果
试验号A B C点滴时间/m in 111112
212219
313317
421318
522122
623220
731223
832325
933124
Ⅰ485358
Ⅱ606662
Ⅲ726160
R24134
优A3B2C2
极差R越大,表明因素对试验指标的影响越大。由表5可以看出,在本试验条件下,A,B,C3个因素对聚苯胺膜耐蚀性影响的重要性依次为A>B>C,最优的因素组合为A
3
B2C2,即苯胺与硫酸浓度比为1∶3、苯胺与过硫酸铵的浓度比为1∶1、反应温度为18℃是最佳的工艺条件。
2.5 阳极极化曲线
图1为裸露的不锈钢试片和最优条件下制备的试片在3.5%NaCl溶液中的阳极极化曲线。由图1可见:无聚苯胺膜的不锈钢试片在腐蚀电位200mV左右电流开始持续上升,表明发生了点腐蚀;当不锈钢表面涂覆了导电聚苯胺膜以后,阳极极化曲线的钝化区域变宽(-750～1200mV),当腐蚀电位超过1200mV后,电流密度急速增大发生了点腐蚀,比裸露的不锈钢试片高出1000mV。这一现象说明聚苯胺膜的存在使得不锈钢的抗点蚀能力大大提高。同时观察溶液中工作面膜层的颜色变化,由绿色→蓝色→紫色,当膜变成紫色后,有点蚀现象发生,观察到曲线电流开始缓慢增大。
图1 试片在3.5%NaCl溶液中的阳极
极化曲线(扫描速率5mV/s)
3 结 论
(1)不锈钢在苯胺-硫酸溶液中,在过硫酸铵氧化剂的作用下,用原位聚合的方法合成了具有耐蚀性的绿色导电聚苯胺薄膜;经过盐酸点滴试验,研究了反应条件对聚合及耐蚀性能的影响,并通过正交试验得到了聚合的最佳工艺条件:苯胺与硫酸的物质的量的浓度比为1∶3,苯胺与过硫酸铵的物质的量的浓度比为1∶1,反应温度为18℃。
(2)在本试验条件下,通过阳极极化曲线测试发现,最优工艺条件下覆盖了聚苯胺薄膜的不锈钢试片在3.5%NaCl溶液中点腐蚀电位发生明显的正移,从裸钢200mV提高到1200mV,提高了1000mV左右。说明该聚苯胺薄膜具有良好的耐腐蚀性能。
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Contents&Abstracts
The Corrosi on Resist ance of Conducti ve Polyan ili n e F il m on St a i n less Steel
BA I Chun2yu,L I A NG Yan2p ing(Depart m ent of App lied Che m istry, Xi’an University of Electr onics Science and Technol ogy,Xi’an 710071,China).Cailiao B aohu2008,41(07),01～03(Ch). Green conductive polyaniline fil m s were p repared on stainless steel u2 sing in2situ poly merizati on method.The effects of the concentrati on rati o of aniline/H2S O4and aniline/a mmoniu m persulfate and reacti on te mperature on the synthesis of polyaniline fil m s were studied.The op ti m al synthetic technics was established by orthogonal text.Moreo2 ver,the corr osi on resistance of the polyaniline fil m s was evaluated u2 sing che m ical titrati on test and electr oche m ical anodic polarizati on curves.The op ti m al concentrati on rati o of aniline/H2S O4and aniline/ persulfate was deter m ined t o be1∶3and1∶1,res pectively,while the op ti m al te mperature was suggested as18℃.The corr osi on poten2 tial of stainless steel coated with polyaniline in the s oluti on of3.5% NaCl increased by about1000mV as compared with blank,indicating that the conductive polyaniline fil m s had good corr osi on resistance. Key words:conductive polyaniline fil m;corr osi on resistance;stain2 less steel
Prepara ti on of Green M i cro2Arc O x i da ti on Ceram i c Coa ti n g on M agnesi u m A lloy
Y AN Feng yun a,F AN S ong2yan b,ZHANGW en2qun b,ZHANG Yu 2hai b(a.State Key Laborat ory of Gansu Advanced Non2ferr ousMetal Materials;b.Key Laborat ory ofM inistry of Educati on f or Non2ferr ous Metal A ll oys,Lanzhou University of Technol ogy,Lanzhou730050, China).Cailiao B aohu2008,41(07),04～06(Ch).Green cera m ic coating was p repared on the surface of AZ91D magnesiu m all oy by m icr o2arc oxidati on.The appearance and compositi on of the cera m ic coating obtained at a K2Cr2O7concentrati on of0.2,0.4,0.6,0.8, 1.0,1.2g/L and1.4g/L and m icr o2arc oxidati on ti m e of5,10, 20,30m in and40m in were investigated.It was f ound that unifor m and dense green ceram ic coating could be p repared fr om the electr o2 lyte containing10g/L Na A l O2,1g/L K2Cr2O7,and a s mall a mount of Na OH and H2O2,via m icr o2arc oxidati on col oring reacti on.It was feasible t o contr ol the col or of the m icr o2arc oxidati on coating by p r operly adjusting the col oring reacti on ti m e,and the col or of the ce2 ram ic coating becomed deeper with increasing col oring reacti on ti m e. Moreover,the green cera m ic coating was composed of M g O,A l2O3, MgCr2O4,and MgCr2O4was the col oring phase.
Key words:m icr o2arc oxidati on;magnesiu m all oys;green cera m ic coating
Syn thesis and Appli ca ti on of Resi n for Ultrav i olet2Curable Ca2 thod i c Electrophoresis Coa ti n g
AN Feng2lei,Y ANG Zhen2qing,L I U Ren,Z HANG Sheng2wen,L I U Xiao2ya(School of Che m ical&Material Engineering,J iangnan Uni2 versity,W uxi214122,China).Cailiao B aohu2008,41(07),07～09 (Ch).An energy2saving and envir on mentally friendly resin used for p reparati on of ultravi olet2curable cathodic electr ophoresis coating was synthesized.Thusβ2hydr oxy2ethyl acrylate(HE A)was used t o par2 tially bl ock t oluene diis ocyanate(T D I),all o wing the generati on of un2 saturated mono mer T D I2HE A containing is ocyanic radical.The unsatu2 rated mono mer T D I2HE A containing is ocyanic radical was then grafted ont o epoxy resin E2552NR3t o p repare water2s oluble phot osensitive resin containing vari ous functi onal gr oup s.The effect of electr ophoresis p r ocess on the depositi on of the resin coating was exa m ined,and the op ti m ized electr ophoresis conditi ons were deter m ined.A t the sa me ti m e,the effects of flash evaporati on te mperature and curing ti m e on the perf or mance of the electr ophoresis coating were investigated.Re2 sults indicated that the op ti m al potential and ti m e for electr ophoresis were80V and100s,res pectively.And the electr ophoresis coating p repared at a flash evaporati on te mperature of80℃and curing ti m e of 5m in sho wed excellent resistance t o s olvent attack.
Key words:cathodic electr ophoresis coating;UV2curing;water s olu2 ble;resistance t o s olvent attack
Sulf i de Stress Corrosi on Crack i n g of X80P i peli n e Steel
Z HANG Peng2cheng1,T ANG D i1,WU Hui2bin1,HUANG Guo2 jian2,WANG Lu2bing1,X I E Guang2yu1(1.Nati onal Engineering Re2 search Center f or Advanced Rolling Technol ogy,University of Science and Technol ogy Beijing,Beijing100083,China;2.Center of Tech2 nol ogy,Anshan Ir on and Steel Gr oup Cor porati on,Anshan114001, China).Cailiao B aohu2008,41(07),10～12(Ch).NACE three2 point standard bent2bea m test was conducted t o investigate the sulfide stress corr osi on cracking(SS CC)of X80grade p i peline steelswith and without all oying ele ments.Thus the corr osi on tests of the p i peline steel in aqueous s oluti on of0.5%CH3C OOH saturated with H2S gas(puri2 ty above99.9%)were carried out at a te mperature of(25±3)℃and for a durati on of200h.Results indicated that the p i peline steel with Cu and N i as m icr o2all oying ele ments had a critical stress of over1390 MPa,while that without Cu and N i registered a critical stress of only 770MPa.The intr oducti on of the Cu and N i m icr o2all oying ele ments led t o the f or mati on of fine and unif or m acicular ferrite m icr ostructure and hence increased resistance t o SS CC.Na mely,in the p i peline steel with the m icr o2all oying ele ments,the hydr ogen p ressure was shared by more grains,leading t o obvi ously increased critical stress and resist2 ance t o SS CC aswell.Moreover,both the high density tangled disl oca2 ti on and p reci p itati on of carbonitrides of m icr o2all oying ele ments in disl ocati on net w orks p layed i m portant r oles as hydr ogen entrappers, which was one of the main reas ons for acicular ferrite t o have excellent resistance t o SS CC.
Key words:sulfide;acicular ferrite;p i peline steel;sulfide stress corr osi on cracking
Corrosi on I nh i b iti on of I ndustr i a l A lu m i n u m by D ecyl am i n e
GE Ke1,WANG Q ing2,Z HANG Sheng2tao1(1.College of Che m istry and Che m ical engineering,Chongqing University,Chongqing 400044,China;2.Chengdu Tongdi W ater Treat m ent Co.,L td., Chengdu610031,China).Cailiao B aohu2008,41(07),13～15 (Ch).The inhibitive perfor mance of decyla m ine t o alu m inu m in hy2 dr ochl oric acid was investigated by measuring the electr oche m ical po2 larizati on curves at a scanning vel ocity of1mV/s.The cathodic and a2 nodic acti on coefficients of decyla m ine at vari ous concentrati ons were exa m ined,and the ex peri m ental data were analyzed and discussed u2 sing ads or p ti on theory.Results sho wed that the inhibitive efficiency of decyla m ine gradually increased up t o a maxi m u m of89.3%with in2 creasing concentrati on,while the acti on coefficients rap idly decreased with increasing concentrati on of decyla m ine and kep t al m ost unchanged at0.01mol/L.I n general,decyla m ine was a kind of m ixed inhibit or, and its ads or p ti on behavi or obeyed Fl ory2Huggins is other m model. Key words:industrial;alu m inu m;inhibit or;decyla m ine;electr o2 che m ical
Corrosi on I nh i b iti on of M ild Steel i n Hydrochlor i c Ac i d by N2 D odecyl Benzotr i a zole Ca ti on i c Surfact an t
WANG Hong2jun,CHE N Hong2ling(College of Chem istry and Chem ical Engineering,Nanjing University of Technol ogy,Nanjing 210009,China).Cailiao B aohu2008,41(07),16～17(Ch).The inhibiti on behavi or of N2dodecyl benzotriazole cati onic surfactant (DBCS)f orm ild carbon steel in1.0mol/L HClmediu m was investi2 gated by means of weight l oss measure ment,polarizati on curve p l ot2 ting,and scanning electr on m icr oscop ic(SE M)observati on.The in2