Controlled release of inhibitors

Kinlen, RJ., C.R. Graham, and Y. Ding. 2004. Corrosion protection of aluminum alloys by controlled release of inhibitors from inherently conductive polymer coatings. Polym Prepr Am Chem Soc Div Polym Chem 45 (2) 146. 

A controlled release of inhibitor can also be achieved when there are interactions between the functional groups of the sol-gel matrix and the inhibitor, as schematically shown in Fig. 9.3(c). An additional inhibition effect was revealed when phenylphosphonic acid was introduced into a hybrid sol-gel film containing phenyl groups (Sheffer et al, 2004). The inhibitor becomes entrapped inside the sol-gel matrix due to specific %-% interactions between the phenyl rings. Sol-gel coatings with phenylphosphonic acid deposited on aluminium substrates demonstrate enhanced corrosion protection attributed to the prolonged release of phosphonate ions. 

Summarizing the information presented above, it can be seen that the direct addition of inhibitors to sol-gel coatings confers additional corrosion protection, and in some cases active protection and self-healing effects. On the other hand, the addition of inhibitors is associated with a number of problems. Therefore, other strategies of inhibitor addition might be used that isolate an inhibitor from the coating components and provide a controlled release of inhibitor on demand. 

Microencapsulation techniques are now being actively developed along directions that will have an important impact on electrochemically based industries. Possibilities include the masking of particulate surfaces to prevent specific (and undesirable) reactions as well as the controlled release of electroactive components or inhibitors into the environment (24). The following examples illustrate these techniques. 

The paper is devoted to development of novel approach to dope coatings with active anticorrosion species with self-healing ability. They contain nanoreservoirs which can store active agents and provide controllable release of them. The titania nanoparticles doped with cerium ions and organic inhibitors were used as nanocontainers to dope the hybrid sol-gel matrix and to provide long-term corrosion protection. 

Activation-triggered delivery of thrombin inhibitors may offer a solution. As an example a recently developed thrombin-responsive starPEG-heparin hydrogel, already introduced in Section 6.4.2, is a promising biofunctional coating for feedback controlled release of heparin at blood-contacting material surfaces. 

F. Presuel-Moreno, M.A. Jakab, N. TaUleart, M. Goldman, and l.R. Scully, Corrosion resistant metallic coatings. Materials Today 11 (10) 14-23,2008 MA. lakab and l.R. Scully, Storage and release of inhibitor ions from amorphous Al-Co-Ce alloys Controlled release on demand. Nature Materials 4 667-670, 2005. 

Yang N, Chen T, Fu J. Controlled release of corrosion inhibitor from intelligent nanocontainers based on acid and base dual-responsive. Gaodeng Xuexiao Huaxue Xuebao/Chem J Chin Univ 2014 35(5) 971-5. 

There are two aspects that are particularly interesting for the future. One is the controlled release of corrosion inhibitors and the other is the stndy of the synergy of these substances with others, organic or inorganic, to improve their inhibition efficiency. 

Control release of RE Inhibitors in self-healing coatings... 

Khramov A.N., Voevodin N.N., Balbyshev V.N., Mantz R.A. (2005), Sol-gel-derived corrosion-protective coatings with controllable release of incorporated organic corrosion inhibitors . Thin Solid Films, 483,191-196. 

Scheme of the controllable release of the inhibitor from LbL nanocontainers and the smart self-healing process (Zheludkevich etal., 2007). 

Controlled release of corrosion inhibitors maybe involved in new-generation corrosion protection coatings based on conducting polymers. Considerable evidence indicates that conducting polymers provide beneficial protection to many metals in a corrosive environment. However, the mechanism by which this protection is afforded is not well understood at the present time. Many studies since the mid 1980s have shown that a coating of PAn, PPy or PTh can inhibit the corrosion rate of mild steel, stainless steel, aluminium ... 

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