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Development of green anticorrosion coatings for steel protection based on environmentally friendly nanoparticles and conducting polymers

Final Report Summary - STEELCOAT (Development of green anticorrosion coatings for steel protection based on environmentally friendly nanoparticles and conducting polymers)

Executive Summary:
Development of green anticorrosion coatings for steel protection based on environmentally friendly nanoparticles and conductive polymers.

STEELCOAT was a project within the EU Seventh Research Frame Programme (FP7), in the area of NMP (Nanosciences, Nanotechnologies, Materials and new Production Technologies).

The long term objective of this three-year project was to reduce the use of toxic and hazardous substances in, and extend the service life of, anticorrosion coatings for steel substrates.

The consortium consisted of 10 partners from 6 different countries developed new environmentally friendly, anticorrosion coatings with extended durability for steel protection. Both high solid solvent-borne and water-borne coatings was developed and the corrosion protection in these novel coatings was achieved by combining environmentally friendly nanoparticles and conductive polymer, together with novel compatible binder polymers.

Project Context and Objectives:
The overall objective of the STEELCOAT project was to reduce the use of toxic and hazardous substances and extend the service life of anticorrosion coatings for steel substrates. The project aimed to develop novel green, environmentally friendly, anticorrosion coatings with extended durability for steel protection. Both high solids (HS) solvent-borne and water-borne anticorrosion maintenance coatings for steel constructions was developed. The corrosion protection in these novel coatings was achieved by combining environmentally friendly nanoparticles, conductive polymers and novel binders.

Project Results:
Unfortunately we are not in a position to make any information public since the data are consider to be exploited. Thus Everything is strictly confidential at present.
Potential Impact:
ENVIRONMENTAL AND HEALTH IMPACT

Hazardous compounds in anti-corrosion coatings

The aim of the STEELCOAT project was to replace hazardous compounds in anti-corrosion coatings with more environmentally friendly conductive polymer/nanoceria/nanoclay systems using green nanotechnology. Several hazardous compounds have been used extensively in anti-corrosion coatings, some of them are being phased out using legislation but equally good alternatives have still to be developed and accepted by the market. Examples of hazardous compounds that have been used in anti-corrosion coatings are given below:

- Hexavalent chromium has been used for more than 60 years in conversion coatings for corrosion protection of steel and other metal alloys. It is today well-known that hexavalent chromium is toxic and carcinogenic (http://www.osha.gov/OshDoc/data_General_Facts/hexavalent_chromium.pdf 2006). Workers who breath hexavalent chromium compounds at their jobs for many years may be at increased risk of developing lung cancer. Breathing high levels of hexavalent chromium can irritate or damage the nose, throat and lungs. Irritation or damage to the eyes and skin can occur if hexavalent chromium contacts these organs in high concentrations or for a prolonged period of time. Moreover, hexavalent chromium compounds are quite soluble in water and can also be found in airborne form. Hexavalent chromium can have a high to moderate, acute toxic effect on plants, birds and land animals. This can mean death of animals, birds or fish and death or low growth rate in plants. Chromium (VI) does not breakdown or degrade easily and there is a high potential for accumulation of hexavalent chromium in fish. Development of alternatives to hexavalent chromium has been difficult because hexavalent chromium displays a combination of unique characteristics. The less toxic cousin of hexavalent chromium, trivalent chromium, has also been used in trivalent chromate conversion coatings, however it is believed that the trivalent chromium can possibly convert to hexavalent chromium in the long run. The European Union RoHS (Restriction of Hazardous Substances) directive, which has been in force since July 1st 2006 (http://www.conformance.co.uk/Resources/ROHS.pdf) allows for a maximum concentration of hexavalent chromium of 0.1% in conversion coatings. Furthermore, the EU End-of-Life Vehicles Regulations that came into force on 15th July 2007 restricts the use of chromium in coatings (Official Journal of the European Communities, L 170/81, 29.6.2002).

-Red Lead . Lead-containing corrosion inhibitive pigments such as red lead pigments have been used in anti-corrosion coatings for many years. However, due to the toxic and carcinogenic (E. K. Silbergeld, M. Waalkes, J. M. Rice, AMERICAN JOURNAL OF INDUSTRIAL MEDICINE 2000, 38, 316) properties of red lead, the highly effective lead pigments can no longer be used for corrosion protection. For example, lead poisoning is a medical condition caused by increased levels of lead in the body. Lead interferes with a variety of body processes and is toxic to many organs and tissues including the heart, bones, intestines, kidneys, and reproductive and nervous systems. It interferes with the development of the nervous system and is therefore particularly toxic to children, causing potentially permanent learning and behavior disorders. Symptoms include abdominal pain, headache, anemia, irritability, and in severe cases seizures, coma, and death. The European Union RoHS directive of 2006 also restricts the use of lead in anti-corrosion coatings.

-Zinc phosphates. For maintenance paints used in steel protection, zinc and strontium chromates have been replaced partly by zinc phosphate. However, zinc phosphate has a limited efficiency so higher coating thicknesses are required to create a sufficient corrosion barrier in these systems. This is not a sustainable solution in the long run due to a larger carbon foot print with thicker organic coatings. Furthermore, zinc phosphate has been classified as hazardous to the environment, in particular to aquatic organisms (“European Union risk assessment report: trizinc bis(orthophosphate)”, 15th Sept 2004. http://ecb.jrc.ec.europa.eu/documents/ExistingChemicals/
RISK_ASSESSMENT/SUMMARY/zincphosphateHHsum077.pdf).
Even though the presence of hexavalent chromium and lead containing inhibitive pigments has been restricted in anti-corrosion coatings since some years, these substances are still present in coatings on objects that have been coated previously. These hazardous coating films are being removed and replaced with less harmful coating systems. However, equally good anti-corrosion alternatives have to be developed and accepted by the market. Until then the cost for corrosion will increase further if not new environmentally-friendly and effective anti-corrosion systems is developed in the near future.

Reducing VOC from anti-corrosion coatings

In general, solvent-borne anticorrosion coating systems have previously provided a better corrosion protection for steel structures than the existing water-borne ones due to the highly hydrophobic nature of coating that effectively prevents water permeation into the steel surface through the coating layer. However, the solvent-borne coatings contribute substantially more to the volatile organic compounds (VOC) emissions compared to water-borne coatings.
The release of VOC from paints and coatings during drying is the most important negative environmental impact from coatings. Virtually everything but the solids in a typical coating formulation is released to the air around the surface being coated. In an enclosed system, such as a paint booth, some of this emission may be captured before release to the atmosphere. Otherwise, it adds to the general atmospheric loading.
Most organics in the atmosphere have a relatively short life. Sunlight is particularly effective at bringing about the oxidation of VOCs, ultimately to carbon dioxide. But it can have some consequences on the way. In the presence of nitrogen oxides (such as are produced by combustion from such sources as vehicles and power plants), photochemically induced VOC oxidation produces ozone as a by-product. Ozone is a health risk at very low concentrations, and is the ultimate risk factor associated with VOC emissions.
It was concluded in a recent Australian study that the total VOC emissions from coatings in Australia was about 36 000 tons in 2007 (from about 0,2 million tons of coatings), and the ozone formation potential was about 106 000 tons (http://www.ephc.gov.au/taxonomy/term/88 “VOCs from Surface Coatings – Assessment of the Categorisation, VOC Content and Sales Volumes of Coating Products Sold in Australia”). Thus, the ozone formation potential is 2.9 times greater than the total VOC emission estimates. The sector of heavy duty coatings (including anti-corrosion coatings) accounts for 7% of the total VOC emissions. However, the percentage of low VOC/water-borne coatings sold within Australia in the sector of heavy duty coatings is only 0.7%. There is thus a huge potential of decreasing the VOC from heavy duty coatings by increasing the percentage of low VOC/water-borne coatings in this sector.
The volume of coatings produced in Europe is about 27 times the volumes in Australia (based on figures from 2003). If we assume the same VOC emission per liter of coating produced in Europe as in Australia, we end up with a total VOC emission from coatings of nearly 1 million tons in Europe. If we assume the same division between coating sectors as in Australia, the total VOC from heavy duty coatings is about 70 000 tons. This number could be decreased substantially if the percentage of low VOC and water-borne coatings could be increased in this sector. The development of low VOC anticorrosion coatings within STEELCOAT can contribute to such an increase.
The European Directive 2004/42/EC limits the VOC content of coatings on the European market (http://eurlex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2004:143:0087:0096:EN:PDF). For example, the maximum VOC content values for primers are set to 30 g/l for water-borne coatings, and 350 g/l for solvent-borne coatings, from 1st January 2010. The corresponding limits for one-pack performance coatings are 140 g/l for water-borne systems and 500 g/l for solvent-borne systems. One of the objectives of the STEELCOAT project is to develop coatings that have VOC contents below 20 g/l for water-borne coatings and 300 g/l for solvent-borne coatings. These values are well below the limits of the EU directive for these types of coatings.
The aim of the STEELCOAT project was to develop anti-corrosion coatings that are water-borne systems or high-solid solvent-borne systems with a low VOC emission. The potential impact on VOC reduction in the anti-corrosion coatings is huge since only 0.7% of the heavy duty coatings today are based on low VOC or water-borne systems (based on figures from Australia).

ECONOMIC AND SOCIAL IMPACT

Cost for corrosion worldwide
The huge economic impact of the corrosion of metallic structures is a very important issue for all modern societies. The World Corrosion Organization (WCO) has recently estimated the annual direct cost of corrosion worldwide to exceed $ U.S. 1.8 trillion, which is equal to 3-4% of the Gross Domestic Product (GDP) of the industrialized countries (“Global Needs for Knowledge Dissemination, Research and Development in Materials Deterioration and Corrosion Control”, G. Schmitt, May 2009, http://www.corrosion.org/images_index/whitepaper.pdf). The corresponding figure for the US has been determined by the Federal Highway Administration (FHWA) to be $U.S. 276 billion per year in 2001 (or 3.1% of the US GDP).
There is to our knowledge no similar investigation of corrosion costs in Europe however since the technological situation in Europe is quite similar to that in the United States, one can assume a similar number for the percentage of the GDP. If we use a number of 3.14% of the GDP for the Euro zone, we end up with direct costs of corrosion of 250 billion € (W. Fürbeth, M. Schütze, Materials and Corrosion 2009, 60, 481). As a comparison it can be mentioned that the whole budget for the European Commission in year 2009 was 133.8 billion €.
All these figures only takes the direct costs associated to corrosion into account. The indirect costs, such as loss of production, environmental impacts, transportation disruption, injuries and fatalities were estimated to be equal to the direct costs (W. Fürbeth, M. Schütze, Materials and Corrosion 2009, 60, 481). The total corrosion costs are thus 6-8% of the GDP worldwide.
Many different areas are affected by corrosion, for example areas such as production and manufacturing (mining, food processing, agricultural pulp and paper, etc), infrastructure (bridges, railroads, airports, gas and liquid transmission pipelines), transportation (ships, motor vehicles, aircrafts etc), utilities (gas distribution, drinking water and sewer systems etc) and government (defense, nuclear waste storage etc). Thus the cost of corrosion is a worldwide problem that affects the whole modern society.
Carbon steel is the most widely used engineering material today. It accounts for approximately 85% of the annual steel production worldwide (http://www.keytometals.com/Articles/Art60.htm). Despite its relatively limited corrosion resistance, carbon steel is used in large tonnages in many application areas. We have previously presented the total cost of metallic corrosion world-wide per year (3-4% of GDP). Because carbon steels represent the largest single class of alloys in use, it is easy to understand that the corrosion of carbon steels is a problem of enormous practical importance.
Below we will present some different examples of steel constructions where corrosion protection is vital for the durability of the objects, and the cost associated with corrosion protection will be analyzed.

Life cycle cost analysis of coating systems for structural steel:
The Duncan Group in the US has provided some data for the life time cost for anticorrosion coating of structural steel (http://www.duncangalvanizing.com/life-cycle-costing-steel/). As an example they have calculated the life time cost for steel coated with an inorganic zinc rich primer, a tie coat of high build polyamide epoxy and a topcoat of aliphatic urethane (Reference coating in Table 1). The total life time of the construction was set to 50 years and in the example a construction of 200 tons of structural steel was used. The data are summarized in Table 1 and compared with the corresponding cost using a new STEELCOAT coating with 25% extended life time. We can conclude that $ 136 322 ($ 565 316- $ 428 994) can be saved by using the STEELCOAT coating with 25% extended service life. This amount is almost as high as the cost for the initial coating of the steel construction.
Table 1: The life time cost for anticorrosion coating of structural steel (http://www.duncangalvanizing.com/life-cycle-costing-steel/)
Category With Reference coating With STEELCOAT coating
Initial coating cost $ 170 000 $ 170 000
Years until first maintenance is needed 21 years 21*1,25=26,25 years
Maintenance intervals 16 years 16*1,25=20 years
Cost per maintenance event $ 218 100 $ 218 100
Maintenance cost per year $ 13 632 $ 10 905
Total cost after 50 years $ 565 316 $ 428 994

Windmills
Wind energy parks are being installed at many places in the world, both onshore and offshore. In Germany, about 20 000 windmills produce about 3% of the German electric energy. The installation of another 20 000 wind mills is planned in the North and Baltic Seas in the next 10 years (“Global Needs for Knowledge Dissemination, Research and Development in Materials Deterioration and Corrosion Control”, G. Schmitt, May 2009, http://www.corrosion.org/images_index/whitepaper.pdf). Huge corrosion problems can arise due to the hostile environment in which the offshore windmills have to work. The severity of corrosion varies according to the different marine zones (see Table 2). The splash zone of the structures suffers the most severe corrosion with 0.4 mm corrosion of steel per year. In the area of offshore wind mills there is a huge need for environmentally friendly anti-corrosion coatings with excellent corrosion protection properties since maintenance here can be difficult and expensive. Also, the alternative power industry is looking for innovative coating solutions that make the whole value chain environmentally friendly. The relative cost of the coating material is almost always insignificant compared to the total cost of maintenance, including work force, for offshore constructions such as windmills.

Table 2: Steel corrosion rates in different marine zones(“Global Needs for Knowledge Dissemination, Research and Development in Materials Deterioration and Corrosion Control”, G. Schmitt, May 2009, http://www.corrosion.org/images_index/whitepaper.pdf)
Marine Zones Corrosion Rates of Steel in Offshore Service (mm/year)
Seamud Zone 0.1
Immersion Zone 0.2
Tidal Zone 0.25
Splash Zone 0.4
Atmospheric Zone 0.1

Safety risks associated with corrosion
The corrosion of steel and other metallic materials and alloys is not only associated with huge costs world-wide. The corrosion of for example steel constructions can also cause safety risks in the modern society. For example, a Berlin Congress Hall collapsed in 1980 due to hydrogen-induced stress corrosion cracking of pre-stressed steel. Furthermore, collapse of suspended ceilings in swimming halls in Denmark and in Uster was caused by chloride-induced stress corrosion cracking (“Global Needs for Knowledge Dissemination, Research and Development in Materials Deterioration and Corrosion Control”, G. Schmitt, May 2009, http://www.corrosion.org/images_index/whitepaper.pdf). Thus, safety risks like these ones can probably be avoided if we in the future can find better corrosion protection systems.
Impact on coating industry and other industries in Europe
The coating industry sector is an important part of the European economy. In Western Europe the domestic sales of coatings was in total 5.4 million tons in 2003, with a value of about 15.4 billion €. The corresponding number for 2010 is more than 17 billion €, according to the European coating organisation CEPE (http://www.cepe.org/ePub/easnet.dll/ExecReq/Page?eas:template_im=100087&eas:dat_im=1002FD).
The EU coatings industries have a strong position, but increasing competition from overseas markets, where labour is cheap, is eroding the leadership of Europe. To change this trend the European industry needs to develop knowledge-based technologies that will increase the technology gap to foreign competitors. The development of new types of functional hybrid coatings based on nanotechnology is part of this important development. In this project we have developed anticorrosion coating solutions for steel with properties beyond the state-of-the-art using nanotechnology. Coating industries can benefit from this technical development, resulting in a sound economical development in this industrial sector with secured employment for a large number of persons.
Companies involved in the production of nanoparticles will also benefit from this development since new market segments will be available for these companies, resulting in new jobs. The new production methods for nanoparticle manufacture which have been developed in this project will lead to new competitive industrial processes for this industrial sector. The sector of nanoparticle production will be strengthened and both large multinational companies as well as small and medium sized companies can benefit from this development.

IMPACT - CONCLUSIONS
Consequently, more sustainable anti-corrosion solutions are needed by society – steel will remain a vital construction medium for many years to come due to the abundance of iron in the Earth’s crust and its strength to weight ratio. However, for damp or exposed environments it needs effective corrosion protection, and occasional maintenance, to ensure safe performance throughout its design life. More sustainable protective coatings need to be developed which use less hydrocarbon resources (lower carbon footprint), are more effective, in thinner films and preferably have superior adhesion from resin binders that can be waterborne or high solid formulations.
Thus, with the improved green, environmentally friendly, anticorrosion coatings which have been developed in the STEELCOAT project it will be possible to reduce the use of toxic and hazardous substances in anticorrosion coatings and to reduce the VOC from anti-corrosion coatings. This will lead to both improved health of workers that are exposed to hazardous substances in anticorrosion coatings and humans in general. Furthermore, the new coating systems will contribute to a cleaner environment in Europe.
With 25% more durable coatings we can also decrease the cost of corrosion substantially. The total cost of corrosion world-wide is today 3-4% of the total GDP. The corrosion costs are thus huge and the impact from a decrease in this cost will thus also be substantial.

List of Websites:
www.steelcoatproject.com
Dr Anders Larsson
tel +46 105166060
Email: anders.larsson@sp.se