Full Description: Title of Innovation: Intelligent Green Conversion Nanocoating. Category: Coatings and linings

Transcription

1 Title of Innovation: Intelligent Green Conversion Nanocoating Category: Coatings and linings Nominee(s): Dr. Atul Tiwari Associate Researcher University of Hawaii at Manoa, Honolulu, HI, USA Web site: Date of Innovation: 01/ /2012 Full Description: When and how was it developed? I was investigating the polymer and silicone based commercial coatings. I observed that most of the coatings suffer failure due to delamination that occurs due to the hydrolysis of adhesive bonds between the metal and coatings. I therefore realized that in order to create an impervious coating, one has to create permanent bonds between metal surface functionality and coating functional groups. I studied the surface of active metals and kinetics of inert oxide layer formation. On understanding the challenge, I selected different chemical components and tried resolving the issues that exist in commercial coatings. The work on this coating started in 2009 and fruitful results were seen in The invention was established after achieving the U.S. patent in 2012.

2 How does it work, in basic terms? Active metal surfaces are covered with natural formed inert oxide layer (IOL). The existing IOL should be removed to enhance bonding between the metal surface and coating. However, rate of formation of IOL is almost instantaneous and therefore mechanical removal of IOL will only result in another reformed layer. Hence traditional coatings cannot form strong bonds and will delaminate with time due to the absence of permanent adhesive bonds. Our SiloXel coating technology consists of chemical ingredients that etch the IOL, allowing other chemicals to immediately react with functional groups that become available on the removal of existing IOL. Special ingredients control the ph of the coating solution and medium. Later, these ingredients act as a buffering agent for the duration of the coating. The SiloXel and active surface groups construct permanent covalent bonds. The entire metal surface and SiloXel coating acts as a thin conversion coating (approximately 5 micron thick) that does not delaminate like other traditional coatings. The SiloXel contains in built titanium chemistry that generates titanium dioxide (TiO 2 ) nanoparticles in situ. Such nanoparticles are self assembled and diminish the chances of agglomeration that occurs in other TiO 2 containing coatings. The presence of silicone and titanium imparts excellent scratch resistant, excellent UV light protection, anti biofouling, anti microbial, and self cleaning characteristics to the coating and substrate. How or why is the innovation unique? The SiloXel composition is unique as it consists of smart chemistry that allows the material to convert the metal surface into thin, hard impervious coating. What type of corrosion problem does the innovation address? The SiloXel coated metal surface remains significantly protected from atmospheric corrosion, microbial corrosion in marine environment, crevice corrosion, and galvanic corrosion. What is the need that sparked the development of the innovation? An annual loss due to corrosion of materials in the United States alone is about $400 billion, and similar economic losses are incurred in the other parts of the world. Such economic losses could be minimized by developing new materials that are an effective barrier against corrosion. There are serious concerns over the use of chromate conversion coating (CCC) as it poses human health related problems. In fact, carcinogenic hexavalent chromium compounds that are being used in coating industry for the corrosion protection of metals is being phased out by EPA in America and REACH regulation in Europe. As a result of objection from the regulating agencies, the manufacturers of CCC and other companies have proposed new coating technologies to protect metals from corrosion damage. However, none of the coating technologies available so far could act as an impervious barrier (similar to CCC) against corrosion. An article titled Reducing the Barnacle Bill, published in The Economist emphasized the immediate need of new coatings to reduce the greenhouse gas emission and spreading of invasive mussels. Industry is desperately looking for a coating that is as effective as CCC and could eliminate or reduce the biofouling activity on metal alloys.

3 Are there technological challenges or limitations that the innovation overcomes? The coating composition contains eco friendly ingredients and creates an impervious barrier that does not delaminate like other polymer based coatings. The viscosity of the coating is low (almost similar to water in flow), therefore it can easily seep into the crevices and areas that are difficult to coat using traditional coatings. The coating process does not need special training or instrumentation. What are the potential applications of the innovation? There is immense impetus toward achieving sustainability by adopting renewal energy resources so that human dependence over fossil fuel could be reduced or eliminated. New green technologies are continuously under development. However, most of such technologies are dependent on materials that degrade in aggressive environmental conditions. For example, the metal frame that host solar panel degrades on exposure to corrosive atmosphere, thereby reducing the service life span of the photovoltaic. The thin and transparent SiloXel can be applied on active metal surfaces and provides adequate corrosion protection. Moreover, SiloXel can be applied on the existing commercial paints and coatings to increase their service life. Several other applications may include coatings for low Earth orbit space craft materials, flame retardant coating, paint restoration, self cleaning, protection blanket for plastics and composites against UV light degradation, anti fouling, finger print mark resistant, etc. In brief, SiloXel could increase the service life span of the existing materials without being noticed or adding an extra weight. How does the innovation provide an improvement over existing methods, techniques, and technologies? The chromate conversion coating is being phased out and alternates are scarce. The green SiloXel coating is thin that contain chemical ingredients easy to dispose. The chemical formulation is easy to mix and apply without any specialized training. SiloXel is a quasiceramic coating that cures in ambient conditions without the need of external heating. Being transparent in appearance, the coated object does not lose its aesthetic appeal. Moreover, the SiloXel can be used as standalone coating or as undercoat or topcoat. In fact, in some cases, topcoats adhered much better to SiloXel compared to the adhesion on bare metal surface. What type of impact does the innovation have on the industry/industries it serves? As per the paint and coating industry review 2009, the global coating market is approximately $100 billion and out of which the market for conversion coating is approximately $300 million. We expect that our SiloXel coating technology could capture this $300 million market and will potentially help in reducing other related losses. Does the innovation fill a technology gap? If so, please explain the technological need and how it was addressed prior to the development of the innovation. As mentioned above, hexavalent chromium based coatings are being phased out. So far industrial sector has tried to fill the gap through trivalent chromium and various conversions using rare earth materials. The problem with these systems is that they do not meet the corrosion protection that hexavalent chromium has to offer. A safer alternative can be formulated for use under paint systems and unpainted systems with a protection mechanism that is flexible and user friendly along with being able to be sprayed on, wiped on, and a dip process. The system type approaches that have undercoat, mid coat, and topcoat do work although the industry is looking for standalone products that can be applied directly to the

4 surface as a very thin film and offer corrosion protection. Additionally, the material should have flexibility and be able to also be painted over and allow excellent paint adhesion that would extend the corrosion protection. Has the innovation been tested in the laboratory or in the field? If so, please describe any tests or field demonstrations and the results that support the capability and feasibility of the innovation. The Siloxel coating has been extensively tested in the laboratory and in several outdoor atmospheric conditions. SiloXel coating has been tested in extreme corrosive conditions such as immersion in NaCl, Na 2 SO 4, real and simulated sea water, immersion in ocean, UV light exposure at high altitude, and accelerated testing as per GM and ASTM standards. Third party validation and testing by independent researchers was also accomplished. Results were compared to the chromated and non chromate treatments and with organic polymer coatings. The SiloXel displayed optimum corrosion protection that was similar to chromate and was much better than non chromated and polymer based coatings. A few results are shown below as Figures 1 & 2. More results are available on request. Is the innovation commercially available? If yes, how long has it been utilized? If not, what is the next step in making the innovation commercially available? We have recently achieved U.S. patent and coating is being commercialized. The first commercial batch of this coating is expected to hit the market in Are you aware of other organizations that have introduced similar innovations? If so, how is this innovation different? We are not aware of any such chemistry available in the market. The international patent cooperation treaty (PCT) search report did not mention any such technology. Are there any patents related to this work? If yes, please provide the patent title, number, and inventor. Patents: US 8,236,203 B2, EP 2,521,755 A2, PCT: WO 2012/ A1 Title: Corrosion Protection Coating and Methods of Making the Same. Inventors: Atul Tiwari & Lloyd H. Hihara Supporting Photos:

5 Figure 1: After approx. 1,300 hours as per ASTM B117. Similar results were obtained after approx. 2,700 hours of exposure. Adequate corrosion protection was achieved by 5 micron thin standalone SiloXel coating. Figure 2: After four months immersion in ocean. Anti biofouling characteristic was demonstrated by SiloXel coating.