# Recent Trends and Progress in Corrosion Inhibitors and Electrochemical Evaluation
## 5 Corrosion Monitoring Techniques
### Self-Healing Study Using A Scanning Vibrating Electrode Technique
Due to a change in pH of the local scribed area because of the attaching of a CI ion, the anodic current flow decreases after 12 h and is completely suppressed after 24 h. Further corrosion of metal will stop after the formation of the passive layer after cationic inhibitors are released from halloysite nanotubes which are mixed with an epoxy monomer matrix. As such, this confirms the self-healing mechanism using the SVET technique [133]. SVET has its own important role in waterborne coatings. Due to strict laws regarding emissions of volatile organic compounds, the market share of waterborne coatings has significantly increased during the past few decades. Waterborne coatings will have the internal ability to repair corrosion damage on their own or by using external components, such as water incorporating self-healing components. For innovative coating goods, sunlight, heat, or mechanical pressure are particularly attractive. Typically, nanocontainers or microcapsules that contain inhibitors or healing agents are impregnated into self-healing coatings. Due totheir size and pore volume, mesoporous silica nanoparticles (MSNs) are excellent nanocontainers. The spontaneous leakage of minute molecule inhibitors from mesoporous is a drawback of these approaches. To overcome these unwanted features researchers have been looking for chemicals that are adhesive in nature to fabricate corrosion inhibitor coatings. One of the most flexible techniques for functionalizing virtually all nanomaterial surfaces is the use of polydopamine (PDA). The adhesive abilities of catechol and amines in mussel adhesive proteins served as its inspiration. This is because PDA has great properties, like increasing wettability [143] and reconstruction of cracked polymer networks [144]. These promising techniques gained the attraction of researchers for the application of PDA into coatings or on metals. Based on a shape memory polymer (SMP) epoxy coating, polyaniline/benzotriazole (PANI/BTA) nanocapsules, and shape memory polymer (SMP) epoxy coating, a three-action self-healing coating was created to help prevent corrosion on carbon steel. As shown in the Figure 16. Additionally, the thermo-responsive SMP coating's ability to minimize scratch size upon heating helped to lessen the quantity of corrosion inhibitors required to completely cover the steel surface. Measurements using electrochemical impedance spectroscopy (EIS) were used to examine how well the coatings containing various amounts of PANI/BTA nanocapsules self-heal. Furthermore, scanning electrochemical microscopy was used to show the combined inhibitory effects of PANI, BTA, and SMP coatings. According to the findings, the healed 0.5 wt.% PANI/BTA coating had a high self-healing efficiency of over 96% and displayed a good self-healing characteristic [145]. Although SVET provides insightful information, it also has several drawbacks and restrictions. For monitoring local electrochemical currents and scanning the vibrating electrode, SVET requires specific equipment. It can be difficult to set up and maintain the equipment, and instrumentation and electrochemistry knowledge may be necessary. The electrochemical activities taking place at the material's surface are the main focus of SVET. It might not offer information about self-healing processes that take place in the majority of the material. Comprehensive SVET tests might take a while to complete since the vibrating electrode needs to be scanned across the sample surface, especially over long periods of time [146]. Figure 16: Saline-responsive triple-action self-healing coating for intelligent corrosion control [145].