Thanks to APCJ: Asia Pacific Coatings Journal, Volume 24, Number 2, pp. 20-21, April/May, 2011, for permission to reprint this article written by Rosa S. Raskin of Rosa S. Raskin & Associates, LLC.
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Research Trends in Innovative Anti-corrosion Additives
"Chemistry, our life, our future" is the theme of the International Year of Chemistry (IYC) 2011 celebrating the 100th anniversary of Madame Marie Curie's Nobel Prize. An IYC chemistry experiment involving school children across the world, entitled “Water: A Chemical Solution,” focuses on technology to supply clean water.1
Coating additives protect water and global infrastructure from fouling and corrosion. Additives enhance anti-corrosion characteristics by modifying coating binder, pigment and/or solvent. Although present in small amounts, single or in combination, additives add desired properties to coatings, must comply with environmental regulations and generally increase cost. 2
Economical, renewable sources of additives are identified in nature, sought in recycling, and display multifunctional properties via nanotechnology and molecular science.
NATURAL INHIBITORS
Chalcones, found in green plants, display slimicidal activity and reduce the hydrophobicity of surfaces. Researchers in India added 2-methoxy-2',4'-dichloro chalcone to a marine paint and observed dead cells on painted surfaces. A reduction in biofilm formation by Vibrio natriegens, a marine bacterium, was observed on the chalcone containing painted polycarbonate (PC), polymethylmethacrylate (PMMA) and glass fiber reinforced plastic (GFRP) used in marine applications. 3
Leaf and plant extracts are potential sources of novel corrosion inhibitors of metals. A Malaysian team identified the ethyl acetate extraction of Uncaria gambir, a Southeast Asian herbal plant found in Malaysia and Indonesia, as inhibiting corrosion of steel in aqueous solutions. Anti-corrosion activitiy of U. gamir was highest at a concentration of 150 ppm in solutions with a pH of 5. 4
Another Malaysian group reports that highly soluble and easy to produce vanillin inhibits corrosion of the aluminum alloy, AA6061, in sea water. In earlier studies, the researchers identified sodium benzoate, tapioca starch and natural honey as corrosion inhibitors of AA6061. 5,6,7
SYNTHETIC COMPOUNDS
Top research studies in 2010 include reports by "the Munich group," a collaborative team of chemists and physicists, who suggest that "guest molecules" placed in individual nano-container cavities enable novel, multifunctional properties in the assembled material. The resulting material displays characteristics not apparent in the single additive. Arrangements of nanostructures in the anti-corrosive chemicals are "moved by light - as if by magic, resulting in complex molecules. 8,9
Conductive polymer coatings prevent substrates from directly contacting corrosive environments, such as sea water. Evidence suggests that alkyd coatings containing electroactive polymers additives, such as polyaniline or polyaniline derivatives, protect carbon steel against corrosion through the formation of protective oxides of Fe2O3 and Fe3O4. 10
MEDICAL IMPLANTS
Reduction of detrimental, slimy biofilms is important in medical and aqueous environments. Inactivation of bacteria on stainless steel surfaces by zeolite ceramic coatings containing silver and zinc ions was demonstrated in 2002 and 2003.11,12
In recent years the use of noble metals, such as silver, has increased due to antibiotic resistant bacteria in complex biofilms. Recent laboratory studies conclude that coating titanium implants with nanoparticle silver ion-coatings prevents biofilm formation, the coatings serving as reservoirs for Ag while limiting the exposure of healthy cells to silver ions. 13,14
Titanium (Ti6AL4V) is used in medical implants and fixation devices per its biocompatibility. Reports suggest that Ti6AL4V may release toxic Al and V ions into the surrounding tissue after implantation. 15 Potential, long-term adverse effects include implant losening and deosteointegration. Zeolite coatings are proposed to prevent release of toxic ions and enhance osteointegration by matching the mechanical properties of bone. Zeolite MFI coatings, described by researchers from the University of California, are synthesized on Ti6AL4V. The coating shows excellent adhesion by incorporating titanium from the substrate within the zeolite framework. The zeolite coatings eliminate release of cytotoxic Al and V ions over a 7 day period. 16
RECYCLING
Korean researchers used magnetic enzyme carriers to improve the recycling of antifouling enzymes that prevent the biofouling of membranes in advanced wastewater treatment systems.17
Extracting useful chemicals from toxic wastes is not a new concept. Toxic garbage, such as cigarettes butts numbering in the trillions, can be "recycled". A Chinese team identified nine compounds in cigarette butt extracts that inhibit metal corrosion of N80 steel used in undersea, oil industry pipelines.
Corrosion inhibitors detected in water/cigarette butt extracts by liquid chromatography, mass spectrometry and an infrared reaction analysis include but are not limited to: N-nitroso-nornicotine, nicotine, cotinine, 2,2-dimethyl-2,3-dihydrobenzofuran-7-ol, 5-(4,6-dichloropyridine-3-yl)pyridine-1(2H)-carboxamide, 6-(2,6-dichlorophenoxy)pyrimidine-2,4-diamine, 1,5-dihydroxy-anthraquinon, rutin, beta-carotene-4,4'-dione.18
China, the third largest user of cigarettes, may take the lead in recycling cigarette filters to extract useful chemicals from the toxic waste stream. 19
CONCLUSION
Corrosion is destructive and costly. Identifying biological, chemical and/or physical methods to unlock biofilm formation via coating additives continue as key objectives.
Research trends include identifying natural extracts, creating new compounds via biomimicry and nanotechnology, studying conducting polymers, incorporating noble metals in coatings and recycling waste streams. The goal is to reduce costs of environmentally friendly additives that protect our marine infrastructure, water quality and human health.
REFERENCES
1. IPY, International Year of Chemistry 2011. http://www.chemistry2011.org accessed January 16, 2011.
2. Bieleman, Johan (editor). Additives for Coatings. Wiley-VCH, 2000.
3. Sivakumar, P.M. et al. 2-Methoxy-2',4'-dichloro chalcone as an antimicrofoulant against marine bacterial biofilm. Colloids and Surfaces B: Biointerfaces, Volume 81, Issue 2, pp. 439-446, December 2010.
4. Hussin, Mohd. Hazwan et al. Electrochemical studies of mild steel corrosion inhibition in aqueous solution by Uncaria gambir extract. Journal of Physical Science, Volume 21, Issue 1, pp. 1–13, 2010. http://web.usm.my/jps/21-1-10/16753402_21.1.1.pdf
5. Rosliza, R. et al. Study on the effect of vanillin on the corrosion inhibition of aluminum alloy. Journal of Applied Electrochemistry, Volume 40, pp. 833–840, 2010.
6. Rosliza R. et al. Anti-corrosive properties of natural honey on Al–Mg–Si alloy in seawater. Current Applied Physics, Volume 10, pp. 923–929, 2010.
7. Rosliza R. et al. Improvement of corrosion resistance of AA6061 alloy by tapioca starch in seawater. Current Applied Physics, Volume 10, pp. 221–229, 2010.
8. Nanowerk News. Moved by light - as if by magic. January 3, 2011. http://www.nanowerk.com/news/newsid=19574.php?utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+nanowerk%2FagWB+%28Nanowerk+Nanotechnology+News%29
9. Woerdemann, Mike et al. Dynamic and reversible organization of Zeolite L. crystals induced by holographic optical tweezers. Advanced Materials, Volume 22, pp. 4176-4179, 2010.
10. Goncalves, G.S. et al. Alkyd coatings containing polyanilines for corrosion protection of mild steel. Synthetic Metals, Volume 161, pp. 313-323, January 2011.
11. Bright K.R. et al. Rapid reduction of Staphylococcus aureus populations on stainless steel surfaces by zeolite ceramic coatings containing silver and zinc ions. Journal of Hospital Infection, Volume 52, pp. 307-309, 2002.
12. Rusin P. et al. Rapid reduction of Legionella pneumophila on stainless steel with zeolite coatings containing silver and zinc ions. Letters in Applied Microbiology, Volume 36, pp. 69-72, 2003.
13. Secinti, Kutsal Devrim et al. Nanoparticle silver ion coatings inhibit biofilm formation on titanium implants. Journal of Clinical Neuroscience, Volume 18, Issue 3, pp. 391-395, March 2011.
14. Menno, L. et al. New strategies in the development of antimicrobial coatings: the example of increasing usage of silver and silver nanoparticles. Polymers, Volume 3, pp. 340-366. http://www.mdpi.com/2073-4360/3/1/340/pdf
15. Bedi, R.S. et al. Synthesis of zeolite thin films on titanium alloys and biocompatibility testing via electrochemical methods. ECS: Electrochemical Society Meeting 213, Abstract #502, Phoenix, Arizona, May 18-22, 2008. http://www.electrochem.org/meetings/scheduler/abstracts/213/0502.pdf
16. Bedi, R.S. et al. Biocompatibility of corrosion-resistant zeolite coatings for titanium alloy biomedical implants. Acta Biomaterialia, Volume 5, Issue 8, pp. 3265-3271, October 2009.
17. Yeon, KM et al. Magnetic enzyme carrier for effective biofouling control in the membrane bioreactor based on enzymatic quorum quenching. Environmental Science and Technology, Volume 43, Issue 19, pp. 7403-7409, October 2009.
18. Zhao, Jun et al. Cigarette butts and their application in corrosion inhibition for N80 steel at 90 °C in a hydrochloric acid solution. Industrial & Engineering Chemistry Research, Volume 49, Issue 8, pp. 3986–3991, 2010.
19. Dillow, Clay. New use for cigarette butts makes them suddenly worth the cost of recycling. Popular Science, May 14, 2010. accessed online January 8, 2011. http://www.popsci.com/science/article/2010-05/researchers-turn-cigarette-butts-strong-anti-corrosive
Author
Rosa S. Raskin, M.S., M.L.S., proprietor of Rosa S. Raskin & Associates, LLC provides expert information specialist, research and consulting services to clients worldwide. Address: 451 Lassiter Drive, Highland Heights, Ohio 44143, U.S.A., Phone: 440-461-4125, Web: www.raskinfo.com
Email: rosa@raskinfo.com