Corrosion Resistance of Thiourea-Modified Waterborne Acrylic Resin Organic Silane Composite Passivation Film on the Surface of Zn-Al-Mg Plate
For exploring the effect of thiourea on the corrosion resistance of waterborne acrylic resin organic silane composite passivation film on Zn-Al-Mg coating,an aqueous acrylic resin-organosilane was used as the main film-forming material,and different contents of thiourea were added to formulate a chromium-free passivate solution for the composite passivation of Zn-Al-Mg coatings. The particle size of thiourea was measured by Nano ZS90 nanoparticle size analyzer,and the structure of thiourea was tested by Nicolet 6700 Fourier transform infrared spectrometer (FTIR) . In addition,the corrosion resistance of the composite passivation film was analyzed through full immersion test,electro-chemical test and neutral salt spray test,and the effect of thiourea content on the corrosion rate of the composite passivation film was explored. Results showed that thiourea possessed an inhibitory effect on the corrosion resistance of Zn-Al-Mg coatings,but too much thiourea could lead to a decrease in the corrosion inhibition of the passivation film. Compared with three different addition amounts of thiourea,the corrosion resist-ance of the Zn-Al-Mg coating was optimal when the mass fraction of thiourea in the passivation solution was 0.5％. Furthermore,thiourea and waterborne acrylic resin organic silane underwent cross-linking,and after corrosion,they formed a complex with metals,forming a dense network structure,which improved the density of the film layer and reduced the corrosion rate of the film layer.
thioureaZn-Al-Mg coatingpassivation filmelectrochemistryneutral salt spray testcorrosion resistance
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