M. L. Zheludkevich, S. K. Poznyak, L.M. Rodrigues, L.F. Dick, M. G. S. Ferreira

The passive corrosion protection is normally achieved by deposition of organic or hybrid polymer coatings as a barrier layer preventing contact of the metallic substrate with corrosive environment. The active corrosion protection aims at a decrease of the corrosion rate when the main barrier is damaged and corrosive species become in contact with the substrate. This can be achieved by the addition of corrosion inhibiting compounds to the protection system. However, direct mixing of an inhibitor with coating formulations can lead to the important drawbacks decreasing barrier properties of coating and diminishing activity of the inhibitor. The problem of coatings with active protection function becomes more acute due to the up coming restriction of the use of chromates, which are known as the most effective inhibitors but are strongly carcinogenic. The development of a new approach to introduce environmentally-friendly corrosion inhibitors, which can provide prolonged and even “smart” release of the inhibiting species on demand and prevent interaction of inhibitor with coating formulation, becomes an important issue for many industries where an adequate corrosion protection is needed.

 The present work shows a new contribution to the development of a novel protective system with self-healing ability that composed of polymer coating doped with nanocontainers that release entrapped corrosion inhibitor in response to presence of corrosive species. The new nanocontainers for organic and inorganic corrosion inhibitors were developed in this work employing layered double hydroxide (LDH) as nanocarriers for immobilization of active compounds. Mercaptobenzothiazole, 8-hydroxiquinoline and vanadetes were used here as corrosion inhibitors. The corresponding ionic forms of these compounds were introduced to the interlayer space of LDH structure by ion-exchange.

The coating with the nanocontainers reveals enhanced long-term corrosion protection of AA2024 in comparison with the undoped films. This effect is obtained due to regulated release of the corrosion inhibitor triggered by the presence of corrosive anions such as chlorides. The approach described herein can be used in many applications where active corrosion protection of materials is required.