汽车用钢板纳米晶镀锌层在氯化钠溶液中的腐蚀机理

摘要

An nanocrystalline zinc coating was prepared on steel sheet used for automobile in alkaline zinc plating bath.The surface morphology of the zinc coating before and after corrosion in 3.5％ NaCl solution was observed with field emission scanning electron microscope (FE-SEM), and the chemical composition of the corrosion products was analyzed by energy-dispersive spectroscopy (EDS). The electrochemical corrosion behavior of nanocrystalline zinc coating was studied by Tafel polarization and electrochemical impedance spectroscopy (ELS). Results revealed that the zinc coating consists of nanocrystal with grain size from 80 to 100 nm, and the corrosion current density of zinc coating is increased obviously after corrosion in 3.5％ NaCl solution for 24 h and 48 h. There are agglomerate corrosion products on the coating after corrosion for 48 h. The capacitance of the corrosion products is increased while the resistance is decreased with increasing corrosion time.%将汽车用钢板置于碱性镀锌液中电镀,制备了纳米晶镀锌层.采用场发射扫描电子显微镜(FE-SEM)观察镀锌层在3.5%NaCl溶液中腐蚀前后的表面形貌,以能谱仪(EDS)研究腐蚀产物组成,运用塔菲尔(Tafel)曲线和电化学阻抗谱(EIS)考察纳米晶镀锌层的电化学腐蚀行为.结果表明,镀锌层由直径为80～100 nm的针状结构的纳米晶组成;在3.5%NaCl溶液中,经24h和48 h腐蚀后,腐蚀电流密度明显增大;经过48 h腐蚀后,有腐蚀团聚物出现;随着腐蚀时间的延长,腐蚀产物的电阻减小而电容增大.