氢氧化物
钝化
材料科学
腐蚀
铬酸盐转化膜
锂(药物)
氢氧化锂
介电谱
氢氧化锌
金属氢氧化物
涂层
铝
化学工程
盐(化学)
阳极
基质(水族馆)
电化学
无机化学
转化膜
锌
电极
冶金
图层(电子)
化学
离子
纳米技术
有机化学
物理化学
内分泌学
海洋学
工程类
离子交换
医学
地质学
作者
Zachary Bergseth,Xiaoning Qi,Vinod Upadhyay,Dante Battocchi
标识
DOI:10.1016/j.apsadv.2023.100432
摘要
As an effort to replace carcinogenic chromate from protective coatings, researchers are continuously searching and proposing new non-toxic chemicals sharing similar properties: leachable, responsive, and film-forming. Lithium (Li), in the form of either a salt additive in coatings or alloyed with aluminum (Al), is observed to be able to form insoluble protective layers and thus reduce the corrosion rate of the Al substrates. The protective film formed is often composed of Li, Al, carbonate (CO3), hydroxide (OH) etc., sharing similar structure to a layered double hydroxide (LDH) as indicated by several mechanistic studies. The successful formation of the irreversible/insoluble protective film requires oxygen, correct pH, and the right combination of available ion species. In this study, electrochemical impedance spectroscopy (EIS) results show that these leachable inhibitor coatings yield poor barrier properties before and after artificial weathering. Scanning electron microscopy pictures show the growth of an inorganic layer between the coating and aluminum substrate, indicative of the formation of a layered double hydroxide (LDH) structure. Current mapping generated by scanning vibrating electrode technique (SVET) indicates that aerated lithium salt solutions can cause pitting corrosion over bare aluminum, while organic coatings pigmented with lithium were able to keep the surface relatively passive, with and without the presence of a defect. An anodic shift of the surface of the organic coatings pigmented with lithium containing a defect is seen while keeping the surface relatively passive, indicating anodic passivation of the metal surface.
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