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EFFECT OF SOLUBLE SALTS ON UNDERFILM CORROSIONOF ZINC SUBSTRATE AND FAILURE OF THE COATINGS |
Yongxiang Xv;Chuanwei Yan;Yanmin Gao |
北京航空材料研究所 |
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Abstract Effect of 6 soluble salts on under film corrosion of metal and failure of the coatings were studied by means of exposed samples.The results show that the acceleration of NaCl to corrosion of zinc substrate is les s than that of Na2SO4 and similar with that of Na2SO3 and FeSO4.NaNO 3 acceleates greatly blistering of the coatings and affects relatively less the corrosion of the substrate.ZnCl2,however,has no harmful effects either on corr o sion of the zinc substrate or on failure of the coatings,and even has some inhib iting effect on corrosion of the substrate.The reason may be that the corrosion product when there is ZnCl2 is unsoluble Zn5(OH)8Cl2.The order that solu ble salts accelerate underfilm corrosion is as:Na2SO4≈Na2SO3>NaCl≈FeS O4>NaNO3ZnCl2;while the order of accelerating blistering is as:NaNO3 ≈Na2SO4> NaCl>FeSO4≈Na2SO3ZnCl2.Polyurethane coating provides better pro tection than alkyd coating.Because the polarity of the molecule of polyurethane is greater than that of alkyd,the polyurethane coating can provide greater resis tance to O2 than alkyd coating.FTIR analysis shows that H-bond is formed betwe en the water molecule and the C=O group of the coatings,and therefore the water can permeate through the coatings much faster than O2.There is intermolecular H-bond 〖JG(〗O〖ZJZ;Y〗C〖ZJLX,S〗〖SX(B-*9〗H〖〗O〖DD(〗··〖DD)〗〖SX) 〗〖ZJS〗N〖ZJZ;Y〗C〖ZJLX,X;Y〗〖SX(B-*9〗O〖〗H〖DD(〗·· 〖DD)〗〖SX)〗〖ZJX〗N〖ZJZ;Y〗O〖ZJY〗〖JG)〗 in the structure of polyurethane,so the available sites for the water mol lcules to react is less than in alkyd coating.Therefore the capacity of polyu rethane to resist water is better than that of alkyd.
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Received: 12 October 2001
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Corresponding Authors:
Yongxiang Xv
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[1]MorcilloM .Solublesalts:theireffectsonprematuredegradationofanticorrosionpaints[J].Prog.Org.Coat.,1999,36:137-147 [2]MorcilloM ,RodriguezFJ,BastidasJM .Theinfluenceofchlorides,sulphates,andnitratesatthecoating-steelinterfaceonunderfilmcorrosion[J].Prog.Org.Coat.1997,31:245-253 [3]XuYongxiang,YanChuanwei,GaoYanmin,DingJie,CaoChu’nan.Diffusionandexistingformofwatervapourinorganiccoatings[ju].ActaPhys.Chem.Sin.,2002,18(7):649-652(徐永祥,严川伟,高延敏,丁杰,曹楚南.水汽在涂层中的传输行为和存在形式[J].物理化学学报,2002,18(7):649-652) [4]YanChuanwei,GaoTianzhu,ShiZhiming,LinHaichao,CaoChu’nan.EffectofNaCloncorrosionofzincinatmospherecontainingSO2[J].ActaMetall.Sin.,2000,36(3):272-274(严川伟,高天柱,史志明,林海潮,曹楚南.NaCl对含SO2环境中Zn大气腐蚀的影响[J].金属学报,2000,36(3):272-274) [5]WuJinguang.TechnologyandApplicationofModernFouriertrans formInfraredSpectroscopy[M ].Beijing:LiteratureofScienceandTechnologyPress,1994(吴瑾光主编.近代傅利叶变换红外光谱技术及应用[M ].北京:科学技术文献出版社,1994) |
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