Hexacyanoferrate-intercalated Layered Double Hydroxides as solution for Detection of Early-stage Corrosion of Steel

摘要

The in-situ detection of corrosion and failures represents an important stage in the procedures of maintenance of metallic structures. The use of nanotechnology embedded in the protective coatings is a promising way to develop user-friendly and cost-effective corrosion detection systems and has to be explored by the coating industry. Several groups have already reported the use of coating systems containing pH indicators and fluorescent probes to detect the corrosion of the substrates. The interest of encapsulating these indicators to prevent undesired interactions and leaching from the coating has also been argued.In this work, layered double hydroxides (LDHs) are intercalated with hexacyanoferrate to be used as corrosion indicator coating additives. Their structure is characterized as well as their toxicity towards marine species. The nanocontainers are then dispersed in a coating matrix to detect the corrosion of a steel substrate at early stage. Electrochemical impedance spectroscopy measurements are performed to monitor the response of this coating towards immersion in corrosive medium. The reaction of the color indicator with the Fe~(3+) ions liberated during corrosion produces a stable blue precipitate coloring the coating, which could be detected by optical instruments to highlight the zones of failure in the structure.