Coating processes – Removable protective coating applied
Reexamination Certificate
1999-03-31
2003-10-07
Navarro, Mark (Department: 1645)
Coating processes
Removable protective coating applied
C427S156000, C427S212000, C427S213340, C427S384000, C427S414000, C435S252100, C435S252300, C435S252500, C435S253300
Reexamination Certificate
active
06630197
ABSTRACT:
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT
Not applicable.
NON-FEDERAL RESEARCH SUPPORT
The invention described herein was made in the course of or under a contract, RP8044-02, with the Electric Power Research Institute.
FIELD OF THE INVENTION
The present invention relates to the field of prevention or inhibition of degradation of surfaces susceptible to degradation through the use of bacteria which secrete antimicrobial chemical compositions. In particular, the invention relates to the use of bacteria which, either naturally or through the use of recombinant technology, secrete chemical compositions which inhibit the growth of sulfate-reducing bacteria on metals, concrete, mortar, and other surfaces subject to corrosion or degradation.
BACKGROUND OF THE INVENTION
Degradation and corrosion damage imposes an enormous cost throughout the world. In the United States alone, the annual cost of corrosion damage has been estimated to be equivalent to 4.2% of the gross national product (Martinez, L. J.
Metals
. 45:21 (1993)) (hereafter, Martinez, 1993). These large costs could be greatly reduced by better and wider use of corrosion protection techniques.
Microbes contribute significantly to degradation and corrosion damage. When surfaces, and particularly metals, are exposed to natural environments, they are rapidly colonized by aerobic bacteria present in the bulk liquid phase (Geesey, G. G., What is biocorrosion? Presented at the International workshop on industrial biofouling and biocorrosion, Stuttgart, Germany. Springer-Verlag, New York (1990)) (hereafter, Geesey, 1990). The upper layers of this biofilm are aerobic while the regions near the metal surface are anoxic due to the depletion of oxygen by the biofilm (Blenkinsopp, S. A. et al.,
Trends. Biotechnol
. 9:138-143 (1991); Bryers, J. D. et al.,
Biotech. Prog
. 3:57-67 (1987)). Sulfate-reducing bacteria (“SRB”) can colonize these anaerobic niches and thus contribute to corrosion even in an aerobic environment (Hamilton, W. A. Sulphate-reducing bacteria and their role in biocorrosion. Presented at the International workshop on industrial biofouling and biocorrosion, Stuttgart, Germany. Springer-Verlag (1990)) (hereafter, Hamilton, 1990).
SRB have been implicated in the deterioration of metals in a wide range of environments (Borenstein, S. W.
Microbiologically influenced corrosion handbook
. Woodhead Publishing Limited, Cambridge, England (1994) (hereafter, “Borenstein, 1994”); Hamilton, W. A.
Ann. Rev. Microbiol
. 39:195-217 (1985) (hereafter “Hamilton, 1985”); Hamilton, W. A.
Trends. Biotechnol
. 1:36-40 (1983); Hamilton, 1990). Pipelines and off-shore oil rigs in the oil and shipping industries (Hamilton, W. A.
Trends. Biotechnol
. 1:36-40 (1983)), cooling water recirculation systems in industrial systems (Borenstein, 1994; Miller, J. D. Metals, p. 150-201. In Rose, A. H. (ed.),
Microbial Deterioration
, Academic Press, New York (1981)) (hereafter, Miller, 1981), sewage treatment facilities and pipelines (Hamilton,1985); Odom, J. M.
ASM NEWS
. 56:473-476 (1990)), jet fuel tanks in the aviation industry (Miller, 1981), and the power generation industry (Licina, G. J.
Mater. Perform
. 28:55-60 (1989)) (hereafter, Licina, 1989) have all been adversely affected by the growth and colonization of SRB. SRB can cause corrosion of a wide range of metals like low-grade carbon steels (e.g., Borshchevskii, A. M. et al.,
Prot. Metals
. 30:313-316 (1994); Cheung, C. W. S. and Beech, I. B.,
Biofouling
. 9:231-249 (1996) (hereafter, Cheung and Beech, 1996); Dubey, R. S. et al.,
Ind. J Chem. Tech
. 2:327-329 (1995); Gaylarde, C. C.
Int. Biodet. Biodeg
. 30:331-338 (1992)) (hereafter, Gaylarde, 1992); Lee et al.,
Biofouling
7:197-216 (1993); stainless steels, (Benbouzid-Rollet, N. et al.,
J. Appl. Bacteriol
. 71:244-251 (1991); Mollica, A.
Int. Biodet. Biodeg
. 29:213-229 (1992); Newman, R. C. et al.,
ISIJ International
. 3:201-209 (1991)); Oritz et al.,
Int. Biodet
. 26:315-326 (1990)); and copper alloys (Licina, 1989; Wagner, P. and Little, B.,
Mater. Perform
. 32:65-68 (1993)) (hereafter, Wagner and Little, 1993), all of which are frequently used in process, shipping, and power industries. SRB also contribute substantially to the degradation of nonmetallic portions of the world's infrastructure. SRB produce hydrogen sulfide, which is then metabolized by sulfur-oxidizing organisms such as Thiobacillus into sulfuric acid. Sulfuric acid degradation due to bacteria has been found to reduce dramatically, for example, the service life of concrete conduits in water systems. Corrosion damage due to SRB just of metals in the U.S. has been estimated to amount to some $4-6 billion annually (Beloglazov, S. M. et al.,
Prot. Met. USSR
. 27:810-813 (1991)) (hereafter, Beloglazov, 1991).
Conventional corrosion inhibition strategies have included a modification in the pH, redox potential, and resistivity of the soil in which the equipment is to be installed (Iverson, W. P.
Adv. Appl. Microbiol
. 32:1-36 (1987)) (hereafter, Iverson, 1987), inorganic coatings, cathodic protection, and biocides (Jack, T. R. et al., Control in Industrial Settings, p. 265-292. In Barton, L. L. (ed.),
Sulfate
-
reducing Bacteria
. Plenum Press, New York (1995)) (hereafter, Jack et al., 1995) (the entirety of the Barton reference is hereby incorporated by reference). Inorganic protective coatings like paints and epoxies have been used extensively in the past; but, they are not permanent, and the cost of maintaining and replacing them is substantial (Jayaraman, A., et al.,
Appl. Microbiol. Biotechnol
. 47:62-68 (1997) (hereafter, Jayaraman et al., 1997a); Martinez, 1993). With cathodic protection, the cathodic reaction is stimulated on the metal surface by coupling it to a sacrificial anode made of magnesium or zinc, or by supplying an impressed current from an external power supply through a corrosion-resistant anode. The galvanic or impressed current lowers the electrochemical potential everywhere on the metal surface so that metal cations do not form, and no dissolution occurs. ((Iverson, 1987); Little, B. J. et al.,
Mater. Perform
. 32:16-20 (1993)). However, Wagner and Little (1993) report that the use of cathodic potentials up to −1074 mV were not able to prevent biofilm formation.
Biocides have also been used to retard the corrosion reaction in closed systems such as cooling towers and storage tanks (Iverson, 1987)) and are probably the most common method of combating biocorrosion (Boivin, J.,
Mater. Perform
. 34:65-68 1995) (hereafter, Boivin, 1995); Brunt, K. D., Biocides for the oil industry, p. 201-207, In Hill, E. C., Shennan, J. L., Watkinson, R. J. (ed.), Microbial Problems in the Offshore Oil Industry, John Wiley and Sons, Chichester, England (1986); Cheung, C. W. S. et al.,
Biofouling
. 9:231-249 (1996)) (hereafter, Cheung, 1996). Saleh et al. (
J. Appl. Bacteriol
. 27:281-293 (1964)) (hereafter, Saleh et al., 1964) reviewed the use of nearly 200 compounds that are bactericidal or bacteriostatic against SRB. Oxidizing biocides like chlorine, chloramines, and chlorinating compounds are used in freshwater systems (Boivin, 1995, supra). Chlorine compounds are the most practical biocides; however, their activity depends on the pH of the water and the extent of light and temperature (Keevil, C. W. et al.,
Int. Biodet
. 26:169-179 (1990)) (hereafter, Keevil et al., 1990), and they are not very effective against biofilm bacteria (Boivin, 1995, supra). Non-oxidizing biocides such as quartenary salts (Beloglazov, 1991), amine-type compounds, anthraquinones (Cooling III, F. B. et al.,
Appl. Environ. Microbiol
. 62:2999-3004 (1996)) (hereafter, Cooling et al., 1996), and aldehydes (Boivin, 1995) are more stable and can be used in a variety of environments. Use of these biocides suffer from a number of serious drawbacks, including not only cost of the biocides themselves but also the environmental cost of releasing into the water supply large quantities of inorganic compounds.
A f
Earthman James C.
Jayaraman Arul
Wood Thomas K.
Navarro Mark
Regents of the University of California
Townsend and Townsend / and Crew LLP
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