Active corrosion protection

In addition to the above-mentioned passive protection with coatings, active corrosion-protection measures, which intervene in the corrosion reaction, are also available. Examples are ... 

The mechanism by which CPs bring active corrosion protection is their ability to intercept electrons at the metal surface and to transport them outside of the primer. Some electrochemical activity... 

Electrochemical methods, in contrast to chemical methods, provide mainly qualitative data on corrosion systems. They are very suitable for studying corrosion mechanisms and the influence of parameters as well as for investigating the value and effectiveness of active corrosion protection... 

Active corrosion protection with the participation of conductive emeraldine base (EB), based on a spatial separation of cathodic and anodic partial reactions as well as a passivation of the metal substrate. 

The effectiveness of the corrosion protection in all three phases depends on many factors. In particular, the durability of the active corrosion protection depends mainly on barrier properties of both the top coat and PANI primer as well as on the resistance of ES against alkaline media. This kind of protection can take place only by a limited diffusion of water and ions through the coating and moderate electrochemical activities at the metal substrate. In the third phase, only the barrier properties of the PANI-primer/top-coat system are crucially important. 

Tedim, J., Poznyak, S. K., Kuznetsova, A., Raps, D., Hack, X, Zheludkevich, M. L., and Ferreira, M. G. S., Enhancement of active corrosion protection via combination of inhibitor-loaded nanocontainers. Apphed Materials and Interfaces, 2(5), 1528-1535 (2010). 

Buchheit, R.G., Mamidipally, S.B., Schmutz, P., and Guan, H. (2002) Active corrosion protection in Ce-modified hydrotalcite conversion coatings. Corrosion, 58, 3. 

Improved Materials for Active Corrosion Protection Systems... 

R. G. Buchheit, S. B. Mamidipally, P. Schmutz and H. Guan, Active corrosion protection in Ce-modifled hydrotalcite conversion coatings . Corrosion 58, 3 (2002). 

In the first case, encapsulation of REM cations in the matrix of coatings, mainly sol-gel, is of particular interest. The purpose of the incorporation of snch cations in such coatings is to be later released, in a eontroUed way, upon eventual exposure to an aggressive enviromnent, precipitating in the active areas and blocking the corrosion reactions. Thus, this protective system attempts to balance the barrier properties supphed by the coating itself with the active corrosion protection role of the eontained speeies. 

Key words self-healing coating, active corrosion protection, sol-gel coating,... 

In summary, the direct addition of RE inhibitors to a sol-gel matrix offers an additional active corrosion protection effect. On the other hand, the presence of RE salts can negatively influence the adhesion and the barrier properties of sol-gel coating, and can chenucally modify the sol-gel matrix and affect polymerization of the sol-gel system. An additional problem is that soluble RE salts are prone to fast release from the sol-gel coatings, thus reducing their effectiveness in corrosion protection. 

Buchheit R.G., Guan H., Mahajanam S., Wong F. (2003), Active corrosion protection and corrosion sensing in chromate-free organic coatings . Prog. Org. Coat, 47,174. 

Dias S.A.S., Lamaka S.V, Nogueira C.A., Diamantino T.C., Ferreira M.G.S. (2012), Sol-gel coatings modified with zeohte fillers for active corrosion protection of AA2024, Corros. Sci., 62,153-162. 

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