1. College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China 2. College of Materials Science and Engineering, Zhejiang University, Hangzhou 310058, China
The sintering temperature was optimized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TG) in order to analyze the properties and mechanism of low-temperature sintered chemically reactive enamel (LTCRE) coating. Microstructure and corrosion process were analyzed by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The corrosion resistance of LTCRE coated steel was analyzed by salt spray test and xenon aging test. Optimized temperature for LTCRE coating is 500-540 °C, and this coating has dense structure and low porosity. Weight change ratio of LTCRE coated steel is 1.6% of that of uncoated steel in the same corrosive environment, peeling radius of LTCRE coated steel after 800 h salt spray test is only 0.26 mm and resisting time in xenon environment is longer than 500 hours. Results indicate that as an inorganic coating, LTCRE coating has better aging resistance and higher stability than epoxy coating. LTCRE coated steel is effective to prevent the infiltration and spread of corrosive substances because of its dense structure and good chemical reaction. Corrosion products accumulated in the corrosion channel can isolate the steel from corrosion, so LTCRE coating can mitigate further corrosion of steel with defects by healing itself.
为了研究低温烧结活性瓷釉（LTCRE）涂层的性能和机理，利用差示扫描量热法（DSC）和热重法（TG）对LTCRE涂层的烧结温度进行优化，采用扫描电子显微镜（SEM）、X射线能谱分析（EDS）和X射线衍射（XRD）分析涂层微观结构和腐蚀过程，通过中性盐雾试验和氙灯老化试验研究LTCRE涂层钢筋的耐腐蚀性能. LTCRE涂层的优化烧结温度为500~540 °C，涂层具有结构致密、孔隙率低的特点，LTCRE涂层钢筋在腐蚀后的质量变化为普通钢筋的1.6%，800 h盐雾腐蚀后人为缺陷孔的剥离半径为0.26 mm，在氙灯照射下耐老化时长超过500 h. 结果表明，LTCRE涂层作为无机陶瓷涂层，具有比环氧树脂涂层更优异的耐老化性能，具备长期稳定的耐腐蚀能力. 涂层密实少孔的结构和烧结时良好的化学反应使得LTCRE涂层钢筋能够有效阻止外界腐蚀物质渗入与蔓延，即使在缺陷孔发生腐蚀后也能够阻止腐蚀加剧，起到涂层自愈合的效果.
关键词：
活性瓷釉涂层,
微观结构,
耐腐蚀性,
耐盐雾性,
抗剥离性能,
抗老化性
w(C)
w(Mn)
w(Si)
w(S)
w(P)
w(Fe)
0.18
0.41
0.17
0.037
0.026
99.18
Tab.1Chemical components of HPB300 steel bar %
w(P2O5)
w(Al2O3)
w(SiO2)
w(CaF2)
w(B2O3)
w(CaO)
w(Li2O)
w(K2O)
w(Na2O)
w(CoO)
w(NiO)
w(ZrO2)
24.1
15.8
5.8
6.4
9.4
3.4
6.1
11.5
12.1
1.7
2.3
1.4
Tab.2Chemical components of LTCRE coating %
Fig.1DSC and TG analysis of LTCRE coating
Fig.2Surface morphology of LTCRE coated steel bar sintered at different temperature
Fig.3SEM images and EDS analysis of LTCRE/CRE coated steel bar
Fig.4XRD patterns of LTCRE coating
Fig.5Weight change ratio of LTCRE coated/uncoated steel bar
Fig.6LTCRE coated/uncoated steel bars in salt spray test
Fig.7Schemes of corrosion mechanism of FBE and LTCRE coated steel
Fig.8Schemes of defect hole and peeling distance
缺陷孔
LTCRE涂层钢筋1
LTCRE涂层钢筋2
LTCRE涂层钢筋3
平均值
区1
区2
区3
区4
区1
区2
区3
区4
区1
区2
区3
区4
缺陷孔1
0
0
0.62
0.3
0.32
0
0.18
0
0
0.48
0
0
0.26
缺陷孔2
0
0
0
0
?
?
?
?
2.2
1.69
0.23
0
0.26
缺陷孔3
0
0.18
0.45
0
0
0
0
0
?
?
?
?
0.26
Tab.3Peeling test results of LTCRE coated steel bar after salt spray test mm
Fig.9Surface morphology of LTCRE coated steel bar before and after xenon aging test
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