Patent Application
20080083435
“UAN” as used herein includes any grade of fertilizer solutions having a mixture of urea and ammonium nitrate in water (described in further detail above), including common grades of UAN 18, UAN 28, and UAN 32, where the numbers indicate total nitrogen content.
“Vessel” as used herein includes any container, cylinder, drum, barge compartment, storage tank, railcar, etc. which is capable of storing or transporting any corrosive substance regardless of degree of corrosiveness. Such vessels are typically constructed of steel.
“Corrosive substances or materials” as used herein include, but are not limited to fertilizer solutions, nitrogen-based solutions, urea ammonium nitrate solutions, aqua ammonia solutions, urea liquor solutions, ammonium sulfate solutions, molasses, potassium sulfate solutions, molasses, and other similar materials.
The method of the invention includes providing a new or cleaned storage or transport vessel. In one embodiment, the method includes cleaning the inner surface of the vessel. Such cleaning may be accomplished using a variety of techniques including, but not limited to sandblasting, high-pressure water washing (where the water may optionally include additional solvents, cleaners, detergents, or the like), chemical rust removal, and other suitable cleaning means. It is contemplated that any appropriate or suitable method or substance of cleaning the vessel surface or removing rust from the vessel surface may be employed.
In one embodiment, the method includes cleaning the inner surface of the vessel with a cleaning composition including from about 20 to about 40 percent by weight of a chelating or sequestering agent, from about 20 to about 40 percent by weight base, and the remainder water. In a preferred embodiment, the composition includes from about 28 to about 32 percent by weight of an organic chelating agent, from about 25 to about 30 percent by weight of base, and the remainder water. In a more preferred embodiment, the composition includes from about 29 to about 30 percent by weight chelating agent, from about 27 to about 28 weight percent base, and the remainder water. Preferably, the water is deionized water.
In alternative embodiments, the organic chelating or sequestering agent may include organic chelating compounds, such as ethylenediaminetetracetic acid; ethylenediamine; nitrilo-2,2′,2″-triacetic acid; diethylenetriaminepentaacetic acid; 1-(2-pyridylazo)-2-naphthol; 1-(3-hydroxy-6-(hydroxymethyl)-4-oxopyridyl)-2-ethanesulfonic acid; 1,10-phenanthroline; 1,10-phenanthroline-2-carboxylic acid; 1,2-bis(2-aminophenoxy)ethane N,N,N′,N′-tetraacetic acid; 1-hydroxyethylidene-1,1-diphosphonic acid; 1,14-bis(2,3-dihydroxybenzoyl)-5,10-bis(1-hydroxy-2-pyridon-6-oyl)-1,5,10,14-tetraazatetradecane; 2,6-pyridinedicarbohydroxamic acid; 1,2-diethyl-3-hydroxypyridin-4-one; 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid; 1-hydroxy-5-methoxy-6-methyl-2(1H)-pyridinone; 1-methyl-3-hydroxypyridine-2-one; 2′-(2-hydroxyphenyl)-2′-thiazoline-4′-carboxylic acid; 2,2′-(ethylenediimino)dibutyric acid; 2,3-dimercaptopropionic acid; 1,2-bis(3,5-dioxopiperazin-1-yl)ethane; or 3-hydroxy-4-pyridone.
In one embodiment, the basic solution of the cleaning composition includes a monovalent base, such as NaOH, KOH, or the like. In alternative embodiments, the basic solution includes a calcium hydroxide, ammonium hydroxide, magnesium hydroxide, or the like. It is contemplated that any suitable base, such as monovalent base, divalent base, amines, tertiary amines, quaternary amines, quaternary compounds, or combinations thereof may be used.
In one embodiment, the method of the invention includes sandblasting or high-pressure water washing the vessel to provide a fresh, clean surface prior to applying the water-based corrosion inhibitor or the organic solvent-based corrosion inhibitor (described in more detail below). In another embodiment, the vessel is new and thus may not need to be cleaned. Such a cleaner may be applied and used in any suitable fashion, such as spraying, immersion, brushing, rolling, mopping, etc.
It should be appreciated that any appropriate cleaner or cleaning method may be used to remove oxide or rust buildup from the vessel surface. This aspect of the invention includes a new or freshly cleaned surface and a person of ordinary skill in the art may use the methods described herein or any other appropriate or suitable method to attain the clean surface.
In one embodiment, the invention includes applying an effective amount of a corrosion-inhibiting composition to an inner surface of a vessel. The corrosion inhibitor is typically applied to the vessel while the vessel is empty. It should be appreciated that the corrosion inhibitor may be any suitable corrosion inhibitor including water-based and organic solvent-based compositions.
In one embodiment, the corrosion-inhibiting composition is a water-based composition and includes from about 2 to about 16 percent by weight of one or more corrosion inhibitor formulations, from about 0.3 to about 1.2 percent by weight glycol ether, from about 7 to about 12 percent by weight naphthenic oil (from about 80 to about 120 cP), and the remainder water. In a preferred embodiment, the corrosion-inhibiting composition includes from about 2 to about 6 percent by weight of a first corrosion inhibitor formulation, from about 2 to about 6 percent of a second corrosion inhibitor formulation, from about 0.5 to about 0.9 percent by weight glycol ether, from about 7.5 to about 10.5 percent by weight naphthenic oil (from about 90 to about 110 cP), less than 1 percent by weight preservative, and the remainder water. In another preferred embodiment, the corrosion-inhibiting composition includes from about 3.8 to about 4.1 percent by weight of a first corrosion inhibitor formulation, from about 3.7 to about 4.2 percent of a second corrosion inhibitor formulation, from about 0.6 to about 0.8 percent by weight glycol ether, from about 8.8 to about 9.6 percent by weight naphthenic oil (from about 99 to about 105 cP), less than 1 percent by weight preservative, and the remainder water.
In alternative embodiments, the corrosion inhibitor formulations may include Alox 165, 165L, 318FS, 319FS, 606, 606-55, 606-55HF, 606-70, 940AS, 1727DS, 2211Y, 2213CS, 2213D, 2278S, 2280S, 2289S, 2290AS, 2290S, 2296; Aqualox 2268S, 2320S, 2328S; Addco CP-OB-2; or combinations thereof, and the like (each listed formulation available from Lubrizol Corporation, Wickliffe, Ohio).
It is contemplated that the glycol ether may include 2-methoxyethanol; 2-ethoxyethanol; 2-butoxyethanol; 2-propoxyethanol; 2-phenoxyethanol; 2-(2-methoxyethoxy)ethanol; 2-(2-ethoxyethoxy)ethanol; 2-(2-butoxyethoxy)ethanol; 2-(2-propoxyethoxy)ethanol; 2-(2-hexyloxyethoxy)ethanol; 2-[2-(2-methoxyethoxy)ethoxy]ethanol; 2-[2-(2-ethoxyethoxy)ethoxy]ethanol; 2-[2-(2-butoxyethoxy)ethoxy]ethanol; 2-[2-(2-propoxyethoxy)ethoxy]ethanol; combinations thereof, and the like.
Representative preservatives include 1,3-dimethylol-5,5-dimethyl hydantoin, iodopropynyl butylcarbamate; 1,3-Bis(hydroxymethyl)-5,5-dimethylimidazolidin-2,4-dione (32 solution in water); 1,3-dimethylol-5,5-dimethyl hydantoin; 1-bromo-3-chloro-5,5-dimethyl hydantoin; combinations thereof, and the like.
In another embodiment, the corrosion-inhibiting composition is an organic solvent-based composition and includes from about 25 to about 50 percent by weight of one or more corrosion-inhibiting formulations (as described above for the water-based composition), and from about 50 to about 75 percent of paraffinic solvent. In a preferred embodiment, the composition includes from about 35 to about 45 percent by weight of the corrosion-inhibiting formulation, and from about 55 to about 65 percent by weight of the paraffinic solvent. In another preferred embodiment, the composition includes from about 50.9 to about 60.5 percent by weight of the paraffinic solvent.
In alternative embodiments, the paraffinic solvent may include any suitable hydrocarbon fluid. For example, in one embodiment, the solvent has an aniline point from about 67° C. to about 77° C., aromatics content from about 0.08 to about 0.22 percent by weight, initial boiling point from about 159° C. to about 210° C., flash point from about 40° C. to about 85° C., and specific gravity from about 0.77 to about 0.82 (at 15.6° C.). In a preferred embodiment, the paraffinic solvent has an aniline point from about 68° C. to about 74° C., aromatics content from abut 0.09 to about 0.16 percent by weight, initial boiling point from about 188° C. to about 194° C., flash point from about 62° C. to about 65° C., and specific gravity from about 0.78 to about 0.80 (at 15.6° C.). In another preferred embodiment, the paraffinic solvent has an aniline point from about 71° C. to about 73° C., aromatics content from abut 0.095 to about 0.11 percent by weight, initial boiling point from about 189° C. to about 192° C., flash point from about 63° C. to about 64° C., and specific gravity from about 0.785 to about 0.796 (at 15.6° C.).
Though not required in accordance with the invention, it should be appreciated that the above-described corrosion inhibitors may include adjuncts, such as preservatives, other solvents, other corrosion inhibitors, and bulk corrosion inhibitors. Furthermore, it is contemplated that these corrosion inhibitors may be applied using any number of techniques, as determined by the user of ordinary skill in the art. For example, these techniques may include spraying with any appropriate spray apparatus, rolling using a paint roller or the like, brushing using a paintbrush or the like, swabbing using a mop or the like, or by using any other suitable method or technique.
In one aspect, the method may be combined with bulk inhibitors, such as Corrogard™ IWC-36, IWC-235, or IWC-278; NITROSolve™ 110, 200, 300, or 330 (available from Nalco Company® in Naperville, Ill.); or the like. In alternative embodiments, the bulk corrosion inhibitors may include silicates, borates, molybdates, tungstates, combinations thereof, or any other suitable bulk corrosion inhibitor(s). Under certain conditions, a synergistic effect is observed when the method of the invention is combined with a bulk inhibitor, as described in the Examples below.
In another embodiment, the method of the invention includes a drying step. This step includes exposing the treated surface to flowing air and appropriate temperature conditions for a sufficient period to allow evaporation of the water or organic-solvent of the corrosion inhibitor. Such drying may include several alternative methods, including letting the surface naturally air-dry, exposing the surface to an appropriate temperature with an adequate volume of circulating air for a sufficient amount of time, or combinations thereof. Factors affecting appropriate drying conditions include the particular type of solvent used, especially whether the solvent is aqueous or organic, the ambient temperature, and the ambient humidity. Of particular importance is the type of solvent used for the corrosion inhibitor. For example, an organic solvent-based corrosion inhibitor (high volatile organic chemical (“VOC”) content) would require different drying conditions than a water-based corrosion inhibitor (low VOC content). The conditions employed should be sufficient to evaporate the solvent, thus leaving the corrosion inhibitor adsorbed to the inner surface of the vessel.
It is contemplated that conditions such as drying temperatures, airflow, and time of exposure to heat and airflow will need to be adjusted to accommodate ambient conditions and the VOC content of the solvent. A person of ordinary skill in the art should easily be able to understand and make these adjustments. For example, if the corrosion inhibitor includes a water-based solvent, longer drying times and possibly increased temperatures will generally be required because water is a low VOC solvent. Further examples are provided below.
It should be appreciated that the drying step may, in some embodiments, require airflow. The user may dry the treated surface using techniques such as exposing to a blast of warm air for a sufficient period, naturally air-drying, or exposing to ambient heat if the temperature is sufficiently warm. It is contemplated that any method or technique of introducing airflow into the vessel may be used, including an exhaust fan, duct fan, or any other suitable air-circulating device. In some of the embodiments described, an external or internal heat source may be required to facilitate evaporation of the water or organic solvent from the treated surface. The heat may be applied either directly or indirectly to the treated surface. Alternative heat sources may include heat generated via: electricity; petroleum-based or other fuel sources; steam or boiler system; kinetic means; or heat generated using any suitable energy source using any suitable heat-generating device.
The following examples illustrate experiments used in testing the effectiveness of the invention (Examples 1 to 3) and methods for carrying out the invention (Examples 4 and 5) and should be understood to be illustrative of, but not limiting upon, the scope of the invention defined in the appended claims.
To illustrate the effectiveness of an exemplary corrosion-inhibiting composition (RustpHree™ 4746A available from Nalco Company® in Naperville, Ill.) in the presence of bulk corrosion inhibitors, mild steel test coupons as above were separated into three experimental groups and a fourth control group, as shown in Table 1. The three experimental group test coupons were pre-treated (i.e., coated) with RustpHree 4746A and air-dried. The control test coupon was not pre-treated (i.e., no coating and no bulk inhibitor). Each test coupon was submerged in a constantly stirred (about 400 rpm stir speed) volume of test solution for a 45-day period. Stirring at this rpm simulated high shear to demonstrate persistence of the RustpHree 4746A coating. The base test solution in each sample was ammonia-stripped UAN 32 (having a starting pH of about 5.9). As shown in Table 1, amounts of the bulk corrosion inhibitors NITROSolve 110 or NITROSolve 200 were added to certain samples.
A corrosion rate for the untreated control and the RustpHree 4746A only test coupon was measured in mils per year (“MPY”), determined by direct coupon weight. Because the corrosion rates for the test coupons having RustpHree 4746A in combination with a bulk corrosion inhibitor were too small to determine by direct coupon weight (thus demonstrating the synergistic effect of the combination), total solution iron levels were measured to determine MPY corrosion of those test coupons. The test method for calculating total iron levels was the Ferrozine calorimetric analysis method (available from Hach, Inc., Loveland, Colo.). Using the untreated control test coupon as a baseline, the results indicate a substantial reduction in test coupon corrosion rate in the presence of RustpHree 4746A, with a greater reduction observed in the presence of bulk corrosion inhibitors.
This example illustrates and compares the effectiveness of RustpHree 4746A and PROTEXO™ 1125 (available from Nalco Company® in Naperville, Ill.) as corrosion inhibitors in both the absence and presence of bulk corrosion inhibitors. Mild steel test coupons as above were separated into five experimental groups and a sixth control group, as shown in Table 2. The experimental group test coupons were either pre-treated with RustpHree 4746A and air-dried or pre-treated with PROTEXO 1125 and air-dried. The control test coupon was not pre-treated (i.e., no coating and no bulk inhibitor). Each coupon was submerged in a constantly stirred (about 400 rpm stir speed) volume of test solution for a 17-day period. Stirring at this rpm simulated high shear to demonstrate persistence of the coatings. The base test solution in each sample was ammonia-stripped UAN 32 (having a starting pH of about 5.7). As shown in Table 2, 110 ppm of the bulk corrosion inhibitor NITROSolve 220 was added to certain samples.
A corrosion rate for each coupon was measured in MPY, determined by direct coupon weight. As seen in Table 2, using the untreated control test coupon as a baseline, the results indicate a substantial reduction in test coupon corrosion rate in the presence of both RustpHree 4746A and PROTEXO 1125.
Donut-shaped mild steel (i.e., non-galvanized) test coupons of about 1.4 inch outer diameter, 0.5 inch inner diameter, and 0.1 inch thickness were cleaned with a solvent and visually examined for any metallurgical flaws. Any coupon suspected of having flaws was rejected and not used in the study. Test coupons were either pre-treated with RustpHree 4746A or were not pre-treated, as above. The coupons were dipped one time each day for 15 minutes into UAN 28 and were then held in the vapor space above the UAN solution in semi-sealed containers at room temperature for 45 minutes thereafter. This test was repeated each day over the course of 13 days.
Table 3 shows the results of the 13-day test cycle, which indicate a substantial reduction in relative corrosion rate for pre-treated versus untreated test coupons. Column 1 describes the test coupon sample. Column 2 indicates the calculated relative corrosion rate (based upon coupon weight) in MPY. Column 3 indicates the relative percent corrosion in comparison to untreated test coupons.
An effective amount of RustpHree 4746A was applied to the inner surface of a 100-ton railcar (i.e., about 20,000 gallon capacity) being about 46-feet long and having about a 9-foot diameter. The railcar was constructed of A-516 grade 70 steel that was about 7/16 inch thick. The railcar's welds met DOT 111A199W1 specifications.
In this example, about 4 gallons of the relatively high VOC content (about 5.8 pounds per gallon of mineral spirits or other paraffinic or organic solvent) corrosion inhibitor was sprayed. The ambient air temperature was approximately 85° F. and the relative humidity was about 50 to 60 percent. Exposing the railcar to sunlight for 24 to 48 hours was sufficient for complete solvent evaporation (the internal temperature of the railcar is estimated to reach about 150 to 160° F. due to sun exposure). In this embodiment, less stringent drying conditions are required because of the high VOC content.
An effective amount of PROTEXO 1125 was applied to the inner surface of a 100-ton (i.e., about 20,000 gallon capacity) railcar. In this example, about 4 gallons of the relatively low VOC content (about 0.06 pounds per gallon) was sprayed. To effectively dry the applied PROTEXO 1125, an air nozzle was inserted into the railcar's man-way dome and air heated to about 200° F. air was introduced at a flow rate of about 1,700 cubic feet per minute for about 3 hours. The heat was subsequently turned off and the same flow rate of cool (about 70° F.) ambient air continued for an additional 12 hours to sufficiently dry the inner surface.
It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the invention and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.
