# Recent Trends and Progress in Corrosion Inhibitors and Electrochemical Evaluation
## 5 Corrosion Monitoring Techniques
### Self-Healing Study Using A Scanning Vibrating Electrode Technique  
Extrinsic self-healing corrosion protection coatings have gained a lot of interest because of their ability to stop the spread of damage by releasing corrosion inhibitors from micro/nanocarriers. The main storage sites for the healing agents are micro/nanocarriers or microvascular networks, which essentially decrease undesired interactions with the bulk coating and also make on-demand and controlled release possible. After unwanted external damage, self-healing materials have the ability to actively heal, extending the lifespan of organic coatings. Metal structures are typically shielded from corrosion by organic coatings, which are typically applied to the surface in liquid form and allowed to dry into a solid surface. Metallic coatings are applied by plating the target's surface with a thin layer of metal. Nanofibers, nanotubes, and electrospun nanofibers are a few examples of the many different types of carriers that are used to encapsulate corrosion inhibitors or self-healing chemicals. The problem of damaged coatings and under-film corrosion is addressed by coatings with encapsulated corrosion inhibitors as a form of self-healing technique. Corrosion inhibitors, as self-healing materials released from the damaged part of coatings, react with a metallic surface to form a passivation layer on the damaged metallic surface, thereby inhibiting the transportation of corrosion factors to the metal substrate and hindering further electrochemical reactions on the metal substrate. The scanning vibrating electrode technique (SVET) gives information about the corrosion initiation in a specified small area. SVET is run by non-instructive scanning and vibrating probe measurement, and also maps the electric field obtained in a plane that is above the electrochemically active surface. This helps quantify the local electrochemical and corrosion events in real time. The action of CI coating for the protection of corrosion is also studied in this method [140]. The coating structure can incorporate self-healing capabilities using a variety of methods. For instance, some polymers have the ability to absorb water and swell, covering and safeguarding the substrate surface under the damaged area [141]. The sol-gel approach is another way to make organic coatings capable of self-healing gel techniques as explained in the paper [142]. Owing to the abovementioned properties of SVET, many researchers have used this technique for the analysis of the coating's ability to resist corrosion. We discussed some of the studies performed using this method. By using the scanning vibrating electrode approach, the self-healing and corrosion protection abilities of the smart coatings are assessed. The vibrating electrode moves over the coated surface to sense the current flow that is naturally produced by the corrosion process. Therefore, a 3D current density map is plotted using the measured current density for a given area. In these graphs, the current flow is directly proportional to the spikes which appear on the 3D graph. The spikes are directly proportional to the corrosion rate [131]. According to the studies carried out by [PERSON] et al. [132] the different current density maps were obtained according to the exposure time of corrosive media on the scribed area. The experimental results showed that there was an increase in the anodic current (AC) in the scribed area of the bare substrate, which indicates accelerated corrosion and an absence of barrier protection. However, the matrix sol-coated substrate exhibited a decrease in AC current for 12 h before increasing. Current results confirm that these coatings provide good barrier protection.