Progress 12/01/02 to 11/30/04
Outputs
The effectiveness of various types of ion exchange cellulose as corrosion inhibitors in protective coating systems was assessed. Two base polymer coating systems (vinyl and coal-tar epoxy) were considered; a commercial corrosion-resistant paint was used as the control system. The following types and dosages of ion-exchange celluloses (and resins) were investigated: (1) 1% (by weight of vehicle) strong-base ion exchange cellulose in OH, PO4, SiO3, BO3, NO2, SO4 and NO3 forms; (2) 1% weak-acid ion exchange cellulose (starch citrate in H form) by weight of vehicle; (3) 2% strong-base ion exchange cellulose in OH form; and (4) 1% and 2 % strong-base ion exchange resin in OH form. Different coating formulations were evaluated based on salt-fog and wet-dry corrosion, water resistance, pull-off adhesion strength, and abrasion resistance tests. Test data for scribed coated specimens subjected to salt-fog corrosion experiments for 1944 hours (81 days) indicated that
incorporation of relatively low dosages of ion exchange celluloses of selected forms into coal-tar epoxy and vinyl paint led to improved corrosion resistance. In the case of coal-tar epoxy, corrosion resistance was enhanced when 1% strong-base ion exchange cellulose in NO2, BO3 and SiO3 forms or 2% strong-base ion exchange cellulose in OH form were introduced into the paint formulation. In the case of vinyl paint, incorporation of 1% strong-base ion exchange cellulose in SO4, SiO3 and BO3 forms led to improved corrosion resistance. Salt-fog corrosion test data for unscribed coated specimens indicated that coal-tar epoxy paints with 1% strong-base ion exchange cellulose in NO3, OH and SiO3 forms offered improved corrosion resistance when compared with coal-tar epoxy paint without ion exchanger. Vinyl paints with 1% strong-base ion exchange cellulose in NO3, NO2, PO4, SiO3 and BO3 forms provided improved corrosion resistance when compared with paints of similar formulation without ion
exchanger. Wet-dry corrosion resistance test data on scribed coated specimens indicated that coal-tar epoxy paints with 1% strong-base ion exchange cellulose in NO3, OH and SiO3 forms, and vinyl paints with 1% strong-base ion exchange cellulose in OH form offered improved corrosion resistance when compared with similar pint formulations without ion exchanger. In the case of unscribed coated specimens, coal-tar epoxy paints with 1% strong-base ion exchange cellulose in OH form and vinyl paints with 1% strong-base ion exchange cellulose in NO3 and OH forms provided improved corrosion resistance. when compared with control paint formulations without ion exchanger. Tests on water resistance, adhesion capacity and abrasion resistance of various paint formulations indicated that ion-exchange cellulse systems which enhance the corrosion resistance of protective coatings can also yield favorable effects in terms of moisture and abrasion resistance and adhesion capacity of coating systems.
Impacts
The technology which is subject of this project promises to develop value-added markets in a key economic sector for chemically modified celluloses (emphasizing those derived from crop residues). The annual costs of metallic corrosion in the United States are estimated at 350 billion dollars or 4.2 percent of our GNP. Annual expenditures in the U.S. on protective coatings for corrosion resistance exceed 100 billion dollars. The project seeks to open this vast market to celluloses derived from different sources, in particular from agricultural residues which are abundantly available (320 million tons per year in the United States) and are mostly of little monetary value. The targeted markets can consume close to 300,000 tons per year of ion-exchange cellulose at an attractive (manufacturer-level) sales price of 5,000 dollars per ton, which is competitive against today's generally hazardous corrosion-inhibiting chemicals.
Publications
- No publications reported this period
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Progress 10/01/02 to 09/30/03
Outputs
The main thrust of the research project is to develop a new generation of effective and environmentally friendly corrosion protection coatings which incorporate bio-based ion exchangers to neutralize corrosive solutions diffusing through the protective coating towards metal surfaces. During this reporting period, alternative bio-based anion exchangers and protective coating formulations were selected for protection of steel against corrosive environments. Diffusion and ion-exchange theories were used to develop design methodologies for selection of the dosage of ion-exchange fillers in corrosion-protection coatings. Thorough experimental studies were implemented to assess the impact of various bio-based ion exchangers on the integrity and corrosion protection attributes of different coating systems. The selected bio-based ion exchangers represent different sources of raw materials, emphasizing agricultural by-products that can add value to agricultural activities.
These bio-based ion exchangers were acquired, converted to different forms (with different mobile ions offering dirrerent corrosion protection qualities), and then milled and incorporated into protective coatings. Examples of protective mobile ions considered so far include: OH-, BO3-, NO2-, SO3-, NO3-, and PO4-. Two different coating formulations based on epoxy and vinyl resin systems are under consideration in the project. Various resin systems differ in terms of the potential impact of ion exchangers on their curing process. Refined coating formulations incorporating bio-based ion exchangers at different dosages (ranging from 2.5% to as high as 12.5% by weight of the binder in coating) were prepared and applied to steel specimens subjected to standard surface preparation schemes. The coating systems were initially evaluated based on their thickness, abrasion resistance, adhesion capacity, and moisture resistance. The effectiveness of coatings embodying different types and dosages
of bio-based ion exchangers in protecting steel specimens against corrosion were assessed through performance of different corrosion tests on scribed and unscribed coating systems. The experimental data generated to date indicate that strong-base anion exchangers with the following mobile ions offer a desirable balance of corrosion protection and physical attributes: OH-, NO2-, SO3-, and BO3-. Lower dosages of these ion exchangers yield more favorable results. Compatibility of the ion exchanger with curing of the coating seems to be a fundamental factor in selection of ion exchangers best suiting particular coating formulations. The design methodologies developed based on diffusion and ion-exchange theories indicate that relatively low dosages of ion-exchanger (below 1% by weight of resin) would be sufficient to render protective effects against corrosive salt solutions diffusing through the coating towards metallic surfaces. The progress to date has been on schedule, and the results
indicate that the project is progressing smoothly towards accomplishing its objectives.
Impacts
The technology which is subject of this project promises to develop value-added markets in a key economic sector for chemically modified celluloses (emphasizing those derived from crop residues). The annual costs of metallic corrosion in the United States are estimated at 350 billion dollars or 4.2 percent of our GNP. Annual expenditures in the U.S. on protective coatings for corrosion resistance exceed 100 billion dollars. The project seeks to open this vast market to celluloses derived from different sources, in particular from agricultural residues which are abundantly available (320 million tons per year in the United States) and are mostly of little monetary value. The targeted markets can consume close to 300,000 tons per year of ion-exchange cellulose at an attractive (manufacturer-level) sales price of 5,000 dollars per ton, which is competitive against today's generally hazardous corrosion-inhibiting chemicals.
Publications
- No publications reported this period
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