摘要
采用开尔文探针研究了相对湿度(RH)为75%和33%时,Al-0.63Mg-0.28 Si合金在原始浓度0.05～0.3 mol/L、体积6μL的MgCl_2液滴作用下的腐蚀行为。由于液滴水分蒸发,在合金表面形成直径约2.9～3.2mm的MgCl_2薄液膜。当开路电位基线在基本维持稳定(-0.3～-0.5 V_(vs SCE))的基础上重复出现电位突降而后立即回复的电位噪声时,对应于亚稳孔蚀的不断形成与钝化,合金表面生成直径小于3μm的亚稳孔蚀。当开路电位缓慢下降至-0.7～-0.8 V左右并维持稳定时,对应于合金表面丝状腐蚀的形成与生长。在RH=33%气氛中,合金表面只发生亚稳孔蚀。在RH=75%气氛中,当初始浓度0.3 mol/L和0.2 mol/L时,24 h内合金主要发生亚稳孔蚀;当浓度下降至0.1 mol/L时,合金表面发生稳定腐蚀(丝状腐蚀),且丝状腐蚀发生在液滴边缘并向外扩展;当浓度进一步下降至0.05 mol/L时,发生稳定腐蚀的几率下降,24 h内主要发生亚稳孔蚀。气氛湿度降低,单位时间内亚稳孔蚀数目降低;而相同气氛湿度条件下,随原始MgCl_2液滴浓度降低,单位时间内亚稳孔蚀数目增加。
The corrosion behavior of A1-0.63Mg-0.28Si alloy under MgCl2 solution drops with initial concen- tration of 0.05 mol/L-0.3 mol/L and volume of 6 pL in the environment of relative humidity （RH） 75% and RH 33% were studied by using Kelvin Probe. In these two environments, because the water in the drop is evaporated, a thin MgCl2 solution layer with a diameter of about 2.9-3.2μm forms on the alloy surface. As the open circuit potential （OCP） baseline keeps stable at -0.3- -0.5 Vvs SHE, there exists potential noise that the OCP repeatedly exhibits a sudden decrease and then immediate recovery, which is associated with initiation and re-passivation of metastable pits with diameter less than 3 #m. When the OCP baseline decreases slowly to -0.7,- -0.8 V and keeps stable low, stable filiform-like corrosion occurs and develops. In the environment of RH 33%, only metastable pitting corrosion occurs within 24 h. In the environment of RH 75~, as the initial MgC12 concentration is 0.3 mol/L and 0.2 mol/L, the main corrosion form is metastable pitting corrosion. As the initial concentration is reduced to 0.1 mol/L, stable filiform-like corrosion always occurs on the drop edge and grows outward. As the initial concentration is further decreased to 0.05 mol/L, the likelihood of stable corrosion is lowered, and the main corrosion form is metastable pitting corrosion within 24 h. The number of metastable pits every unit time is increased with RH of the environment. Meanwhile, in environment of the same RH, it is increased with the decrease in initial concentration.
出处
《中国腐蚀与防护学报》
CAS
CSCD
北大核心
2011年第6期467-472,共6页
Journal of Chinese Society For Corrosion and Protection
基金
国家自然科学基金项目(50771092
21073162)资助
