热镀锌钢盐雾腐蚀行为及机理研究

Study on salt spray corrosion behavior and mechanism of hot dip galvanized steel

通过研究中性盐雾腐蚀研究热镀锌钢的腐蚀行为,明确不同时间周期下热镀锌钢的腐蚀过程及腐蚀机理.模拟中性盐雾加速试验,通过失重法、SEM、XRD以及拉曼光谱等分析方法,对比不同腐蚀周期对热镀锌钢腐蚀行为的影响.结果表明:随着腐蚀周期的增长,热镀锌钢的腐蚀速度呈现出逐步增大并最终趋于平稳的状态.腐蚀过程中,腐蚀表面首先出现白色和浅黄色锈迹,随着腐蚀的加剧,腐蚀表面逐渐出现褐红色以及黑色锈迹,腐蚀层也逐渐由较为致密转变为蓬松、开裂、剥落,腐蚀产物主要以ZnCl_(2)、Zn(OH)_(2)、γ-FeOOH、Fe_(3)O_(4)以及Fe_(2)O_(3)为主.热镀锌钢30天的腐蚀过程主要可以分为三个阶段,分别为:镀锌层的保护阶段,镀锌层的破损阶段以及镀锌层的失效阶段.其中,以镀锌层的破损阶段腐蚀速率为最高,该阶段腐蚀产物以黄锈(γ-FeOOH)和红褐色锈(Fe_(2)O_(3)、Fe(OH)_(3))为主,腐蚀产物蓬松,且出现裂纹,为下一步的腐蚀提供通道.随着腐蚀周期的增加,碳钢基体逐渐暴露,此时腐蚀速率下降且趋于平稳,腐蚀产物以红褐色锈及黑锈(Fe_(3)O_(4))为主,腐蚀产物蓬松易脱落.

In this work,the corrosion process and corrosion mechanism of hot-dip galvanized steel under different time periods were clarified through investigating the corrosion behavior of hot-dip galvanized steel under neutral salt spray corrosion.The neutral salt spray accelerated test was simulated,and the influence of different corrosion periods on the corrosion behavior of hot-dip galvanized steel were compared by weight loss method,SEM,XRD and Raman spectroscopy.The results showed that the corrosion rate of hot-dip galvanized steel gradually increased and finally became stable with the increase of corrosion period under 8 corrosion periods.In the process of corrosion,white and light yellow rust appeared on the surface at first.With the intensification of corrosion,maraud-red and black rust gradually appeared on the surface,and the corrosion layer gradually changed from relatively compact to fluffy,cracking and peeling.The main corrosion products are ZnCl_(2),Zn(OH)_(2),γ-FeOOH,Fe_(3)O_(4) and Fe_(2)O_(3).The 30-day corrosion process of hot-dip galvanized steel can be divided into three stages:the protection stage of galvanized layer,the damage stage of galvanized layer and the failure stage of galvanized layer.Among them,the corrosion rate is the highest in the damage stage of galvanized layer,and the corrosion products in this stage are mainly yellow rust(α-FeOOH)and reddish-brown rust(Fe_(2)O_(3),Fe(OH)_(3)).The corrosion products are fluffy and cracked,providing a channel for the next step of corrosion.With the increase of corrosion period,the carbon steel substrate gradually exposed,at this time,the corrosion rate decreases and tends to be stable,the corrosion products are mainly red brown rust and black rust(Fe_(3)O_(4)),and the corrosion products are fluffy and easy to drop.