Study of the corrosion protection offered by self-healing coatings by using localized electrochemical techniques

Description

The research topic concerns the interpretation of protection mechanisms of coatings applied on a metal substrate using localized electrochemical techniques. This study is situated within the context of developing new types of coatings protecting metal substrates. The developed coatings must have anti-corrosion properties to protect the metal substrate. Two types of protection are identified:

• passive protection characterized by the formation of a barrier between the metal and the corrosive environment;
• active protection related to the coating’s ability of self-healing upon the occurrence of defects.

Passive protection of sol-gel, organic or hybrid coatings is evaluated by electrochemical impedance spectroscopy (EIS) which is a macroscopic technique. Follow up during the immersion time in the corrosive environment enables to characterize the durability of coatings. To protect against occurring surface damage, corrosion inhibitors are dispersed in the coating, the release of these inhibitors enabling to counteract the corrosive effects caused by the external environment diffusing at the metal-substrate interface. Local electrochemical techniques (such as the vibrating electrode probe (SVET) and the electrochemical microscope (SECM)) are then used to assess the active protection of the coatings. Given the complexity of the studied systems (coatings, inhibitors, electrolyte, interface, metal substrates, measurement artefacts), full control and interpretation of the parameters involved in the mechanism of localized protection of coated and scratched metal substrates require extensive studies and will be explored during the thesis.