Trivalent Chromium Conversion Coating Formed on Hot Dip Zn-55Al-1.6Si Coated Steel

6th Annual International Conference on Material Science and Environmental Engineering

材料科学;生态环境科学

Li, Yan^1 ; Pan, Jie^1 ; Qi, Jiantao^2

School of Material Science and Engineering, China University of Petroleum (East China), Qingdao, Shandong

266580, China^1

College of Chemical Engineering, China University of Petroleum (East China), Qingdao, Shandong

266580, China^2

关键词: Conversion coatings;    Corrosion current densities;    Electrochemical polarization measurement;    Forming parameters;    Salt spray corrosion;    SEM and EDS analysis;    Trivalent chromium;    Trivalent chromium conversion coating;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/472/1/012075/pdf
DOI  :  10.1088/1757-899X/472/1/012075

来源: IOP

【 摘 要 】

Trivalent Chromium Process (TCP) coating on hot dip Zn-55Al-1.6Si coated steel was investigated by XPS, SEM and EDS. The XPS revealed that aluminium oxides enriched the conversion coating surface. SEM and EDS analyses indicated that composition and microstructure of the conversion coating were not uniform on the dendrite and inter-dendrite regions within the Zn-Al alloy coating, and a small amount of spherical precipitation with the same composition as the conversion coating was detected in the zinc-rich inter-dendrite region. The optimal forming parameters of dilute passivator determined by salt spray test and orthogonal test is: 40°C, 50 vol.% and 3 min. In addition, the salt spray corrosion resistance of the optimal conversion coatings can reach 192 h, and the optimal TCP coating can reduce the cathodic corrosion current density in 0.05 M NaCl solution by an order of magnitude due to the electrochemical polarization measurements.