铝合金表面防腐蚀处理新工艺_郭增昌

工艺研究

铝合金表面防腐蚀处理新工艺

郭增昌, 王云芳, 王汝敏, 熊艳丽(西北工业大学化工系, 陕西西安710072)

[摘 要] 为避免铬酸盐处理铝合金造成环境污染, 以环境友好的 缩水甘油醚丙基三甲氧基硅烷(GPT M S) 和正硅酸乙酯(TEOS) 为原料, 用溶胶 凝胶法在室温下制备有机 无机杂化溶胶, 经浸涂并室温固化后在铝合金表面形成涂层。通过X 射线衍射、反射吸收红外光谱、腐蚀测试技术(盐雾试验和动电位扫描) 和标准胶带方法对涂层的结构、耐腐蚀性及粘结力进行了分析和测试, 结果表明, 由于形成了致密的非晶态涂层, 同时涂层和基体界面之间形成了稳定的Ai O Si 化学键, 该涂层具有优异的耐腐蚀性能和强的结合力。

[关键词] 防腐蚀; 铝合金; 杂化涂层; 溶胶 凝胶法[中图分类号]T G174. 44

[文献标识码]A [文章编号]1001-1560(2005) 04-0025-03

0 前 言

铝合金表面防护常采用铬酸盐转化层, 以提高涂层的疏水性及其与随后涂层的粘结性。由于六价铬对环境和人体有严重危害, 近年来其应用已逐渐受到限制。为此, 许多研究者一直在寻找环境友好、对人体无危害的铬酸盐替代品, 而环境友好的有机改性硅烷(Ormo sils) 具有独特的结构和性能, 已受到研究者的极大关注

[2~8]

[1]

1 试 验

1. 1 材料及药品

试片材料为非轧制状态的LY12铝合金, 尺寸125m m 80mm 1mm, R a 1 m 。GPT MS; TEOS; 0. 05mol/L 乙酸; 美国3M 公司Fluor ad TM 非离子氟素表面活性剂(FC 4430) ; 去离子水; 硝酸; 铬酐; 脂肪族胺; 丙酮或丁酮; 铝合金清洗剂L8140。以上药品均为工业级。1. 2 铝合金表面预处理

铝合金的表面预处理的两种不同工艺路线:工艺路线1:脱脂(丙酮或丁酮擦洗) →冷水洗→碱液清洗(45~60g/L L8140, 通气搅拌, 57~63 , 10~15m in) →温水洗(30~50 , 2min) →喷淋水洗→脱氧(10%H NO 3+1%NaBrO 3+0. 01%偏钒酸铵) →喷淋水洗→干燥→浸涂偶联剂溶液(由GPTM S 在0. 05mo l/L 的醋酸溶液中水解30min 而制得, 其中GPTM S 为5. 5%~6. 0%) →常温干燥1h →浸涂杂化溶胶(铝试片在溶胶内保持5~10min, 提出速度10cm/min) →固化→测试。

工艺路线2:脱脂(丙酮或丁酮擦洗) →冷水洗→碱液清洗(45~60g/L L8140, 通气搅拌, 57~63 , 10~15m in) →温水洗(30~50 , 2min) →25

。

有机硅烷可与基底铝合金形成极强的M e O Si 键, 而硅烷的有机部分又可与表面聚合物涂层(底漆) 形成化学键结合, 硅氧烷键的形成可大大提高表面聚合物涂层与基体铝合金的结合力, 同时也使铝合金的抗腐蚀性得以提高。

本研究采用sol g el 工艺, 使一定物质的量比的3 缩水甘油醚丙基三甲氧基硅烷(GPT MS ) 和正硅酸乙酯(T EOS) 进行酸催化水解, 将预先处理的LY12铝合金在该杂化溶胶中浸涂后进行常温固化, 最终在铝合金表面形成GPTM S/TEOS 杂化转化层, 用电化学测试技术、盐雾试验、浸渍腐蚀试验对该转化层进行了腐蚀测试, 并与传统的LY12铝合金铬酸盐转化层进行了比较。

[收稿日期] 20050127

[9~11]

铝合金表面防腐蚀处理新工艺

喷淋水洗→脱氧(70~105g /L 硝酸, 22 5~26 3g/L Cr 6+, 室温, 用H F/NH 4H F 2调节腐蚀速度) →冷水洗→喷淋水洗→铬酸盐阳极化[30~52g/L Cr (游离) ; 30~107g/L Cr (总) , 38~42 , 55~60min]→喷淋水洗(﹤35 , 0. 5~15. 0min, 水中总固溶物 100mg/L, 漂洗水中CrO 3含量不高于100m g/L ) →封闭(25~35m g/L K 2Cr 2O 7, pH =6~7, 95~98 , 40~45m in) →测试。

1. 3 溶胶的制备及铝合金表面转化层的形成

按n(GPT MS) /n(TEOS) =3(物质的量比) 分别把二者加入到0. 05mo l/L 乙酸缓冲溶液中(按R=15~16比例添加, R 为水量与有机硅量之比) , 强烈搅拌陈化1h, 在室温下密闭的容器中搅拌陈化3d; 取陈化好的溶液V mL 用1. 7~2. 0倍的水稀释并强烈搅拌, 再超声处理1~3min, 然后加入固化剂(三乙烯四胺) 0. 025V mL 和复合非离子表面活性剂(全氟烷基聚乙烯醇和全氟烷基酯化物) 0. 01V mL, 采用浸涂法(提拉速度10~12cm/min) , 把已表面预处理的铝合金浸入到溶胶中几分钟后提出, 室温固化24h 即形成转化层。为了确定杂化涂层结构, 对其进行了X 射线衍射(XRD) 分析见图1。图1中无尖锐的衍射峰, 所以涂层表现出明显的非晶态结构特征, 图1中衍射数据表明涂层具有纳米特征, 较宽的3个衍射峰处的衍射面间距分别为0. 4, 0. 9, 1. 8nm

。

6+

6+

2. 3 动电位扫描

极化测定前, 试样预先在3. 5%N aCl 溶液中浸2h, 电化学测试试验用M237A 恒电位仪进行, 并由其软件分析记录的数据, 参比电极为饱和甘汞电极, 铂网为辅助电极, 测试结束后利用相应的计算机软件M 352拟合求出腐蚀电位E corr , 腐蚀电流密度J corr , 其大小表示材料的腐蚀程度, 值越大表明腐蚀越严重, 结果见表1。试样暴露在溶液中的面积为1cm , 测试装置见图2, 动电位扫描速度为50mV/min, 扫描范围-1000~+200mV 。

表1 动电位测量结果

LY12处理工艺GPT M S T EOS 溶胶固化膜

未处理的LY12铬酸盐阳极化预处理层

J co rr /(A cm -2) 4. 3 10-91. 3 10-53. 2 10-7

E corr (vs SCE ) /mV

-608-697-

628

2

图2 动电位测试装置示意图

图1 GP T M S T EO S 涂层XR D 分析结果

2 结果与讨论

2. 1 盐雾试验

盐雾试验在西安飞机制造公司的盐雾箱内进行, 将不同工艺处理的试样暴露在盐雾试验箱(5%NaCl 溶液喷雾) 中经168h 后取出观察发现, 表面没有腐蚀现象。2. 2 膜厚测量

试验测得GPT MS T EOS 膜厚度为0. 6~1. 0 m, 铬酸盐阳极化膜层的厚度为2~3 m 。

动电位极化测试结果表明:空白铝合金在3 5%NaCl 溶液中的阳极过程主要为活性溶解, 阴极反应为氧扩散所控制, 腐蚀电位为-697mV, 未显示任何钝化区; 铬酸盐阳极化(Alo dine 1200) 处理试样的腐蚀电位为-628mV, 显示出较小(0. 04V) 的极化区; GPT MS TEOS 溶胶固化处理试样的腐蚀电位为-608mV , 钝化区较大(0. 4V ) , 与铬酸盐阳极化处理时相比, 有机改性硅膜(GPT MS T EOS 溶胶固化保护膜) 具有优异的防腐蚀性能, 这是由于GPT M S T EOS 涂层固化后形成结构致密的纳米膜。测试结果(见图3) 表明, 同等条件下有机改性硅膜比铬酸盐预处理层的耐蚀性好且无

污染。

图3 动电位扫描曲线

26

铝合金表面防腐蚀处理新工艺

2. 4 漆层结合力检查

参照波音公司BSS 7225标准, 用标准胶带(1mm 方格250压敏胶带) 法检查, 参考西安飞机制造公司飞机蒙皮涂层质量检验标准认为, 结合力100%。将涂覆GPTM S T EOS 涂层的材料在20 蒸馏水中浸14d 后, 按上述方法进行检查, 结合力仍达100%。这是由于涂层与铝合金基体形成结合紧密的Al O Si 共价键(图4) , 随着固化温度的提高, Al O Si 峰的吸收强度不断增强所

致。

涂漆前的预处理。这种杂化溶胶引入其他的均匀分散相(氧化锆、氧化钛、氧化铝) 、提高涂层的厚度后, 有望代替底漆使用。

[

参

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[2] 陆 峰, Vanoo ij W J. 铝合金表面硅烷处理后腐蚀

性能的研究[J].材料工程, 1999(8) :18~20.

[3] V reugdenhil A J, Balbyshev V N , Donley M S.

N ano st ructur ed silicon so l g el sur face tr eatments for Al 2024 T 3pro tection[J]. J Co at T echno, 2001, 73(915) :35~43.

[4] Du Y J, Damr on M , T ang G , et al. Ino rg anic/or

g anic hy br id coat ing s fo r aircr aft aluminum allo y substrates[J]. P rog O rg, 2001, 41:226~232.

[5] K ast en L S, Balbyshev V N, Donly M S. Sur face

analyt ical st udy self assembled nanophase par ticale (SN A P ) sur face tr eatments [J ].Pro g O rg Co at, 2003, 47:214~224.

[6] Do nly M S, M antz R A, Balbyshev V N , et al. T he

图4 GP T M S T EO S 涂层的反射吸收红外光谱

self assembled nano phase particale (SN A P )

该杂化溶胶的形成和固化原理见图5, 首先是

四功能的正硅酸乙酯水解形成环状三聚体、四聚体等结构[12], 然后和三功能的GPT MS 水解产物缩聚, 随后环氧乙基与加入的脂肪胺(T ET A) 反应,

固化成膜。

process:a nanoscience appro ach t o coat ing s [J]. Pr og Or g Coat, 2003, 47:401~415.

[7] Castelv et ro V , Vita C D. N anostructured hybrid

materials from aqueous polymer disper sions[J].A d v an Co lloi Inter f Sci, 2004, 108~109:167~185. [8] Schmidu H , L ang enfeld S, N ab R. A new co rr osio n

protectio n coating system fo r pressure cast a lumin ium automo tive pa rts[J].M ateri Desig , 1997, 18(4/6) :309~313.

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t ion and evaluat ion of envir onmentally compliant spr ay coated or mosil films as cor ro sion r esistant treatments for aluminum 2024 T 3[J]. P rog Or g Co at, 2001, 41:261~265.

[10] O sbo rne H J, Blohow iak K Y, T aylor S R , et al.

T esting and evaluat ion of no nchro mated coating sy s t ems fo r aero space a pplicat ions[J]. Pr og O rg Co at, 2001, 41:217~225.

[11] Berw ag en G P, T allman D E. Choice and measur e

ment of cr ucia l aircraft coating s system pr operties [J].Pr og Or g Coat , 2001, 41:201~216.

[12] N g L V , T ho mpson P, Sanchez J, et al. F or matio n

cagelike inter mediat es fr om nonrandom cy clizatio n dur ing acid cat aly zed sol g el po ly merizatio n of tet raethyl ort ho silicate[J]. M acr omo lecules, 1995, 28:6471~6476.

[编辑:魏兆军]

图5 GP T M S T EO S 溶胶杂化及固化原理

3 结 论

LY12铝合金经GPT MS TEOS 杂化溶胶处理, 其表面可形成结构致密的纳米保护膜。由于硅醇与活化处理的铝合金表面形成非常强的M e O Si 化学键, 所以GPT MS TEOS 杂化膜表现出较高的耐蚀性和界面结合力, 该工艺基本可用于铝合金

27

alcohol; anode; o xidation reactio n

Electrochemical Preparation of BaWO 4Film at Room Tempera ture and Its Characterization GA O Dao jiang 1, XI AO Ding quan 2, YU P ing 2, L A I X in 1, BI Jian 1(1. Colleg e of Chemist ry, Sichuan No rmal U niv ersi t y, Chengdu 610066; 2. Co llege of M ater ials Science and En g ineering , Sichuan U niv ersity , Cheng du 610064, China ) Cailiao Bao hu 2005, 38(4) , 18~20(Ch) . BaWO 4cr ystalline film with scheelite st ruct ur e was prepared directly on tung sten flake substrate using r oom t em perat ur e co nstant cur rent galvanostatic method, in an attempt to study the influence o f the electr ochemical pr ocessing co nditions on t he for mation and per formance of the pr epar ed BaW O 4film. T he film fo rming mechanism was also discussed. T hus the as plated film w as char acter ized by means o f X r ay diff raction, scanning electr on micro sco py , and X ra y phot oelectr on spectrosco py. Results revealed that the tar get BaW O 4film w ith sing le tetr ago nal st ruct ur e was unifor m and co mpact. T he o pt imized parame ter s for the elect rochemical r eact ion w ere recommended as cur rent density 1mA /cm 2, pH value of t he elect rolyte 13, electro chemical treatment dur ation 1h.

Key wo rds:BaW O 4film; electr ochemical pr epar atio n; roo m temper atur e; character izat ion

Electrochemical Corrosion Failure of NiC rBSi Welded Surfacing C oating

ZHA O W ei min 1, 2, WA N G Y ong 2, X U E Jin 1, W U K ai yuan 2(1. Scho ol of M aterial Science and Eng ineering, X i an Jiaotong U niver sity, X i an 710049; 2. Schoo l of M echanical and Electr ical Engineering , U niv ersit y o f Petr oleum, Dong y ing 257061, China) Cailiao Baohu 2005, 38(4) , 21~24(Ch). NiCrBSi alloy w elded surfacing co ating w as pr epar ed on the sur face of car bo n steel using ox yacety lene flame, and the co r r osio n failure pr ocess of the allo y surf acing co ating in 3. 5%NaCl so lutio n w as studied using immersing test and alter na t ing current (AC) impedance met ho d. T he potentio static po larization was used to acceler ate the cor ro sion of the N iCrBSi alloy sur facing coat ing w ith excellent cor rosio n resistance. Results show ed that the pitting cor ro sion of the surfacing co ating was mainly att ributed to the impurit y inclusio n. T herefor e, it w as feasible to efficiently incr ease the cor ro sion resistance o f t he surfacing coating by decreasing the amount and vo lume of the included impur ities. M or eover , the surfa cing co ating had stable cor rosion resistance and assumed a lit t le decr ease in the impedance value during t he cor ro sion pr ocess. T he equivalent circuit for the co rr osion sy stem of the sur facing coating w as a typical Randles equivalent cir cuit. If sev ere cor rosion locally occur red on the sur facing co ating and the metal substrate w as par tly ex posed, the impedance of the sur facing co ating wo uld markedly decrease and the cor re sponding equiva lent circuit wo uld change. In this case the sur facing coating wo uld fail even ther e did no t occur larg e scale co upled cor rosion betw een the co ating and the metal subst rate. T he measurement o f the fr ee cor ro sion potential indicated that it was feasible to judg e the cor rosion failure sit uatio n of the N iCrBSi allo y surfacing co ating by monito ring the elect rode cor ro sion potential o f the st ructur al par ts made ther eof.

Key wo rds:met allic surfacing co ating; N iCrBSi co ating; co r r osio n failure; nickel alloy; alt er nating curr ent impedance Environm entally Friendly Surf ace Treatment Process for Corro sion Protection of Aluminum alloys

GU O Zeng chang, W A NG Y un fang , WA N G Ru min, XIO NG Y an li (Depar tment of Chemistr y Eng ineer ing, No rthw ester n Po ly technical U niv er sity , Xi an 710072, Chi na) Cailiao B aohu 2005, 38(4) , 25~27(Ch) . Env ir onmental friendly pro cess w as develo ped to o vercome the pollutio n re sulted fro m chro mate in the surface t reatment o f aluminum al loy. T hus the enviro nmentally friendly g lycidox ypro py ltr i mentox ysilane (GP T M S) and tetr aetho x ysilane (T EO S) wer e br so tar get co at ing w as pr epar ed on the A l allo y sur face by dip coat ing and curing at ro om temperature. T he st ructur e of the coat ing was analyzed by means of X ra y diffr action and r eflec tio n absorptio n infrar ed spectrosco py. T he co rr osion resist ance o f the co ating w as investigated using salt spray test and potentio dy namic scanning test, w hile its adhesion str eng th w as measured using standard adhesiv e tape method. T he re sults sho wed that the coat ing had ex cellent cor rosio n resist ance and high adhesio n str eng th, w hich w as attr ibuted to the dense amor pho us cry stalline hy brid str ucture and stable A l O Si chemical bo nd at the interface o f t he coating and the al lo y substr ate.

K ey wo rds:anticor ro sion; aluminum allo y; hybrid coat ing ; sol g el method

Electroless Ni C r C u P Alloy Plating Technology

1

XI AO Xin , Z HO NG Ping 1, XI A H ai bo 2, CH EN Y ong kang 1(Department of Chemistry and Chem ical Engineer ing , H unan Inst itute of Eng ineer ing, Xiang tan 411104; 2. Sifang Ro lling Stock W or ks, China South L o co motiv e &R olling Sto ck Industry Gr oup Cor po ration, Qing dao 266031, China) Cailiao B aohu 2005, 38(4) , 28~31(Ch) . T he co rr osion re sistance o f electr oless nickel pho sphor us alloy plat ing is un satisfactor y in mo der n industr y. T hus electr oless nickel cop per chro mium pho sphor us alloy plating was dev elo ped to im prov e the comprehensive pro per ties of the N i P alloy plating so as to ex tend its applicat ions in industr y. T he effects of the bath composit ion and o per ating co ndit ion o n the appear ance, depo sitio n r ate, and co rro sion resistance of the tar get N i Cr Cu P a lloy depo sit w ere studied, and the pr operties of the al lo y depo sit w ere inv est igated as well. A s t he results, it w as feasible to deposit the Ni Cr Cu P allo y deposit by adding cupr ic sulfate and chrom ium chlor ide in the tradit ional electr o less N i P plating bath. T he optim ized formulation of the plat ing bath w as deter mined to be 15g /L NiSO 4, 40g /L NaP O 2, 0 2g/L CuSO 4, 0 5g/L N a 2M oO 4, 0 5g/L stabilizing a gent (nitro gen co ntaining or ganic co mpo und o r iodine co nt ai ning compound ) , 40g/L co mplexing agent (polyhydro xy carbo xy lic acid and po ly basic car bo x ylic acid ) , 20g/L CH 3CO ON a, 10g /L CrCl 3, and a pro per amo unt of sur factant (po ly ethylene g lyco l and fluo rine containing surf actant) . T he o ptimal plating parameter s w ere determined to be pH 4 0~5 0, temperature 80~90 , and a dur atio n o f 20min. T he tar get N i Cr Cu P allo y depo sit w as composed of 8%~9%Cr, 2%~3%Cu, and 78%~85%N i, and it was superio r to the conventio nal N i P plating in terms of the fine g ra in structure, brightness, co rr osio n r esistance, po rosit y, and ha rdness. K ey w or ds:elect roless plating ; N i Cr Cu P alloy ; cor rosio n r esist ance; depo sitio n rate

Factors Affecting the C opper Deposition Rate on C arbon Fiber G AO Song 1, 2, Y A O Guang chun 1(1. Schoo l of M ateria ls and M etallur gy , No rtheastern U niversity, Shenyang 110004; 2. Department of Chemistr y, Shenyang Institut e of Chemical T echnolog y, Shenyang 110142, China) Cailiao Baohu 2005, 38(4) , 32~34(Ch) . U nifo rm and thick co pper plating w as depo sited on carbon fiber by combining elect ro less plating copper with electro plating copper. T he ef fects o f fo rmalde hyde, complex ing ag ent, stabilizer, pH v alue, temper ature, curr ent density, and electr olysis time on the deposit ion r at e w ere investigated. T hus the optimal for mulatio n for the cop per deposition on the ca rbon fiber s w as determined, and the r esulting copper plating was character ized using a scanning e lectr on micro sco pe. As t he results, t he optimum for mulatio n fo r the electro less copper plating w as det er mined to be 16g/L CuSO 4 5H 2O, 25g /L EDT A 2N a, 15g/L so dium potas sium t artr ate, 15g/L N aOH , 5mg/L 2, 2 dipyr idine, 15mg /L K 4F e(CN ) 6, and 6mL /L H CH O (A. R. ). It w as able to get r id of the co re blacking of the carbon f iber s making use o f the dev elo ped electr oless Cu plating plus Cu electro plating techno lo gy and the tar get copper co ating w as thick and w ell adher ed to the car bo n fiber s.

; ; ;