MXPA99007276A - Cleaning and covering of conversion of laminated steel articles in calie - Google Patents

Abstract

A process is presented in which hot-steel articles, such as rail cart items, LP tanks and barges, are cleaned and coated by conversion. The cleaning compositions include the aqueous phosphoric acid, and the conversion coating compositions include the aqueous phosphate

Description

CLEANING AND COVERING CONVERSION OF HOT LAMINATED STEEL ARTICLES TECHNICAL FIELD OF THE INVENTION This invention generally relates to the preparation of the hot-rolled steel surface. The invention relates more specifically to a surface preparation method for hot-rolled steel rail cars and other articles.

BACKGROUND OF THE INVENTION Hot rolled and cold rolled steel are used to make a wide variety of products, but each has unique properties depending on the temperature at which the steel has been worked or rolled in relation to the steel's critical temperature range , that is, a temperature range through which steel properties change dramatically. The hot rolled steel supplied by the steel mills is coated with a hard steel oxide layer composed mainly of Fe304, known as "rolling scale", while the cold rolled steel has a smooth surface with very little imperfections. Hot rolled steel also has more rust that is firmly stuck to the surface than cold rolled steel.

As is generally described in the Manual of Metals, Volume 1: Properties and Selection, 8th edition, T. Lyman, Ed. ASME 1961, p. 79, which is incorporated herein by reference: "Hot-rolled sheets are suitable where normal oxide and minor surface imperfections may be acceptable, and are generally used for parts where the Finishing is of secondary importance ... Cold-rolled sheets are characterized by an improved surface finish or tempering and special properties. " These differences are usually taken into consideration when selecting a steel type, as well as a method to clean the surface before applying conversion coatings and paints. The conversion coating usually involves the treatment of the steel to convert the metallic surface into a layer of insoluble inorganic crystals, thereby imparting a corrosion resistance and aiding the adhesion of the paint. The primary conversion coatings are phosphate and chromate, the first one being described in more detail below.

There are some methods to clean iron and steel surfaces. Known methods include acid pickling, acid cleaning, alkaline removal with salt bath, brushing, and detonation or abrasive sanding. In the automotive industry, acid cleaners have been commercially adopted to the same degree as alkaline cleaners.

Both pickling and cleaning involve the treatment of the surface with a caustic solution. A difference between pickling and cleaning is that pickling usually involves immersion, while cleaning commonly involves sweeping or spraying. Another difference is that the cleaning solutions are usually diluted more than the pickling solutions. As described in the Manual Metals, Volume 2: Heat Treatment, Cleaning and Finishing, edition, T. Lyman, Ed. ASME 1964, p. 340, which is incorporated herein by reference: "The distinction between acid cleaning and etching is a matter of degree, and there is often an overlap in the use of these terms. However, in general, pickling with Acid refers to a more severe treatment for the removal of oxide from semi-finished products, forges or smelting while acid cleaning is the term used most often when an acid solution is used for final or near-end preparation of the products. metallic surfaces before plating, painting or storage ". Cleaning solutions can have acid concentrations as dilute as pH 5.5, or as concentrated as acid stripping solutions, for example, 35 vol. of percentage of acid or more. For example, a cleaning solution that has 70 vol. percentage of phosphoric acid is reported in the Manual of Metals, Volume 2 on page 341.

The most common acids involved in pickling are sulfuric and hydrochloric acid, while the acid-cleaning agents most commonly used include organic acids and weaker solutions of hydrochloric sulfuric acid, and a variety of other mineral acids, including acid phosphoric. It is known that cleaners with dilute phosphoric acid leave a slight coating of iron phosphate, which provides a temporary resistance to corrosion and a suitable base for the paint.

Acid cleaning is usually carried out at room temperature, although it is known that heating increases efficiency greatly. When heating is used, usually the acid temperature is maintained in a range of about 140-200 ° F.

Cold rolled steel has long been the preferred construction material in the automotive industry because its good surface quality allows the achievement of high quality paint finishes. In addition, automotive parts and smaller items have been considered docile for chemical cleaning and conversion coatings due to their relatively small size and because those skilled in the art have discovered that cold rolled acer does not have as much oxide. nor lamination scale that avoids the effective use of the mentioned chemical methods.

The steel structures of ships, rail cars, earthmoving machines, power transformer safes are different from those of automobiles because, in addition to being much larger, these items are mainly hot rolled, unlike laminated steel cold The combination of larger size and the degree of rolling scale and rust in the steel structures of ships and rail cars has led to the opinion that these items are not analogous to automotive structures and smaller laminated articles. cold with respect to the techniques of preparation prior to painting, which have limited the acceptance of the methods of pickling and chemical cleaning in the industry d rail cars.

Other methods for cleaning and preparing surfaces include cleaning with power tools, water wash and abrasive injection in water. Cleaning c power tools can eliminate a very high degree rust and lamination scale, but like jet cleaning, power tool cleaning generates large amounts of dust, in addition to consuming large amounts of energy and requires maintenance and replace frequent worn parts. The washing and water equipment requires specialized components to operate at a high pressure medium (3000 psig or more). For example, a pressure pump, and a specialized spray nozzle assembly, as well as large volumes of water are required. This technique can eliminate loose rust but will not effectively remove rust or firm rolling shells. The abrasive injection in water can provide a greater capacity to eliminate rust and lamination scale. However, the abrasive injection in water is what causes most of the concerns in ordinary jet cleaning in addition to consuming large volumes of water.

Due to the disadvantages of these alternative methods, lamination scale and rust on large articles made of hot-rolled steel has conventionally been eliminated by means of jet cleaning, or method for removing mill scale, rust, rust scale , paint or foreign matter through the use of abrasives driven through nozzles or by means of centrifugal wheels. In general, a "Commercial Surface Cleaning Surface Finish" is sought, which is defined by the Steel Structure Painting Council (SSPC) as that which has completely eliminated all oil, rust, dust, rust scale and foreign matter of the surface, and all rust, mill scale and old paint has been completely eliminated with the exception of light shadows, grooves, or discolorations caused by rust stains, rust of lamination scale or light or firm residues of paint or coating that may remain. If the surface is corroded, slight residues of rust or paint may be found on the bottom of the sheet. Under this definition, at least two thirds of each square inch of surface area is free of all visible debris and the remainder is limited to slight discoloration, light staining or firm debris mentioned above.

Three main categories of abrasives used for jet cleaning include "granules", "shot" and "sand". The "granules" mainly include angular metal particles, usually of molten steel which is crushed and hardened, and may be quenched or tempered white cast iron. The granules have an extraordinary power of cort. The "shot" is also metallic, but includes spherical particles or pieces of wire that deform rounded particles during use. The "sand" includes the ordinary silica sand as well as a number of other non-metallic abrasives, including natural minerals, such as garnet, dolomite, pumice, novaculite and quartz stone and also synthetic materials, such as silicon carbide and oxide. of aluminum. These abrasives are adapted to applications in which metal contamination is not desirable.

In the United States, the field of surface preparation for rail cars is handled by Trinit Industries, Thrall and National Rail Car. Each of these companies has used granular blast cleaning for many years, largely due to It has been understood for a long time in the art that blast cleaning with granules is the method of preparation of surfaces more escalabl increasingly for items that have a high degree d lamination and rust scale. Blast cleaning with granules can obtain virtually any degree of cleanliness of an article of any size, from Cleaning to Chorr with Brushing an LP tank with gas grills according to SSPC SP7 (SSPC-SP7), until A White Metal Jet Cleaning of a rail car according to the SSPC SP standard (SSPC-SP5). The SSPC-SP7 standard for Cleaning a Chorr with Brushing stipulates: Removal of loose lamination films, loose rust and loose paint, at the rate specified later, by means of impact of abrasives driven through ducts or centrifugal wheels. It is not intended that the surfaces be free of all lamination scale, paint rust. The remaining lamination, rust and paint chips must be firm and the surface must be sufficiently scoured to provide a good adhesion of the paint ...

The SSPC-SP5 standard for Metal Blanc Blast Cleaning stipulates: Elimination of all lamination films, rust, rust scale, paint or foreign matter by using abrasives driven through centrifugal wheels nozzles. A White Metal Jet Cleaned Surface Finish is defined as a surface with a uniform grayish-white metallic color, slightly hardened to form a suitable anchor pattern for the coatings ...

In addition to cleaning, steel pretreatments may also include chemical conversion coatings to impart corrosion resistance and improve paint adhesion. Although manufacturers do not apply chemical conversion coatings to rail cars, phosphate conversion coatings are applied steel surfaces properly cleaned in other industries. The three main coatings are phosphate conversion or iron phosphate, phosphate of zinc and manganese phosphate.

The phosphate d iron conversion coatings, which are the oldest commercially available phosphate coatings, are used primarily as a base for painting because they provide excellent adhesion and resistance to peeling. However, the automotive industry has come to rely primarily on zinc phosphate for chemical conversion. Zinc phosphate is considered by the automotive industry as a provider of improved resistance to corrosion and greater adhesion of the paint.

The phosphate conversion coatings can be applied by immersion, by sweeping or by spraying the phosphate solutions. The immersion method can be used to apply conversion coatings to small items, while the spray coating can be used to apply phosphate compositions to larger articles, such as transformer casings, which can be up to twenty feet in height. The application by spraying iron phosphate provides a layer of fine crystals which has a bluish tint on the steel surfaces which are substantially free of rust. Generally, the layer has a thickness of 20 to 15 mg / square feet. Phosphate coatings can be dried with different types of kilns, at temperatures up to 400 ° F.

All phosphate conversion coating compositions are acidic. Zinc phosphate can be sprayed at a pH as high as 3, while zinc phosphate dipping solutions are generally maintained within the pH range of 1.8-2.4. The d iron phosphate immersion solutions are commonly maintained within a pH range of 3-6.

The inventor is not aware of any reported conversion coating and spray cleaning to prepare surfaces of large hot rolled steel items, such as rail cars.

SYNTHESIS OF THE INVENTION Although the railcar industry has found that granular blasting is a flexible method to remove up to about 95 percent of the rolling scale, however, it remains a method of preparing maintenance surfaces. intensive and high cost, which incurs even greater costs when attempts are made to eliminate more than approximately 95 percent of the rolling scale, due to the decreased utility in labor investment to try to clean the access areas limited. Not only does the abrasive itself have a limited life and a high replacement cost, without the granular jet cleaning it also presents major safety problems due to eye injuries and poses several serious operational problems. These problems include rapid wear of moving mechanical parts due to dirt and contamination of the lubricants, as well as breakage of parts due to abrasion and clogging. For example, there have been instances of shutdowns due to disconnection of the bits after have been stuck with abrasive. In the same way, the particle elevators have become clogged. In addition, the presence of moisture is a problem with granular jet cleaning methods because the humid causes the abrasive to build up and form solid blocks, which are difficult to dislodge from the equipment, and can jam mobile parts aggravating the This way the problem of abrasion. Once the granules coagulate, then they need to be removed and replaced by new granules. There can be approximately forty to fifty-five 55-gallon drums to be replaced manually, which will require approximately eight hours and three workers, and an entire shift loss. production, in addition to the cost of the granules Finally, the quality of the finish that is achieved by cleaning the jet with granules is limited as a practical asunt. In most commercial applications in which most lamination scale is removed from metal surfaces, a significant amount of rust remains in areas of difficult access. In addition, the areas that are easily accessible remain with a surface profile of 2 - 2-5 thousand., Which is an unequal surface that requires almost twice the amount of paint for the coating. As a consequence, there is difficulty in approaching economically at a "Class A" level in the "automotive quality finish" by means of hot-rolled steel, jet cleaning with granules.

The aforementioned imperfections are focused on the present invention, which, in one of its embodiments, is a process for treating items of rail cars that include hot-rolled steel, and where this process includes, in order: cleaning by spraying acid with a solution that includes phosphoric acid, rinsing after cleaning, spraying phosphate with a solution that includes a phosphate, a rinse after the phosphate spray where the spray, aerosol and vapors of each stage are substantially contained not to be transferred to each of the other stages.

In another embodiment, the invention includes a process for treating articles of riele carts including hot rolled steel, where this process includes, in order: cleaning by spraying acid for 4 minutes with a solution that includes phosphoric acid, rinse by spraying after cleaning, spraying phosphat for 2-4 minutes with a solution that includes a phosphate, u rinsing after the phosphate spraying, and drying and / or curing at 200-400 ° F, where the spray, aerosol and vapors of each stage are substantially contained so as not to pass through each of the other stages.

In another embodiment, the invention includes a process for treating items of rail cars including hot-rolled steel, where this process includes, in order: cleaning by acid spraying for 4-8 minutes with a solution including phosphoric acid, spray rinse after cleaning, phosphate spraying for 2-4 minutes with a solution including a phosphate, and a post-spraying rinse of phosphate, where the spray, aerosol and vapors of each stage are substantially contained not to be transferred to each of the other stages by means of air barriers through which the articles are transported.

In a preferred embodiment, the articles are transported along rails and the spray is applied to the articles as the articles move along the sections. During this movement, the spray, aerosol and vapors of each stage are substantially contained so as not to be transferred to each of the other stages by means of air barriers through which the articles are transported.

In another embodiment, the invention includes a process for treating articles that include hot-rolled acer, where this process includes, in order: cleaning by acid spraying for 1-8 minutes with a solution including phosphoric acid, rinse after cleaning, spraying phosphate with a solution that includes phosphate, and a rinse after the phosphate spray.

In another embodiment, the invention includes a process for treating LP tank items including hot rolled steel, where this process includes, in order: acid spray cleaning for 4-8 minutes with a solution including acid phosphoric, rinsing by spraying after cleaning, phosphate spraying for 2-4 minutes with a solution that includes a phosphate, or rinsing after the phosphate spraying, and drying and / or curing at 300-600 ° F, where the spray, aerosol and vapors of each stage are substantially contained so as not to be transferred to each of the other stages by means of air barriers through which the articles are transported.

DETAILED DESCRIPTION OF THE INVENTION The invention is directed to chemical cleaning and conversion coating of hot rolled steel articles. As used in the specification and claims, a "rail cart article" is defined as an article that includes at least a portion of a rail carriage, an "LP-tank article" is defined as an article that includes at least a part of a Petroleum Liquid tank, and a "barge article" is defined as an article that includes at least a part of a barge.

The process of the present invention is not limited to phosphate conversion chemistries and cleaning specific commercially available acids. However, as a non-limiting example of an acid cleaning composition useful for the present invention, a composition comprising 15-35 percent phosphoric acid and about 0-2 percent sulfuric acid in water can be used. Preferably, the composition contains 0.20-1.0 w / v% iron, and more preferably 0.30-0.35 w / v% iron. In formulating this composition, it was found convenient to use the Parco® 210 Cleaner, obtained from the Henkel Technologies division of Henkel, 32100 Stephenso Highway, Madison Heights, MI 48071. The composition of the Parco® 210 Cleaner is 50-60 per one hundred percent phosphoric acid (Chemica Abstracts No. 07664-38-2), about 1 percent sulfuric acid (Chemical Abstracts No. 07664-93-9), and the rest water. The composition may also contain other components, such as accelerators, sodium phosphate, sodium nitrate. It was discovered that steel and steel wool were convenient sources of iron as an additive for the acid composition.

To obtain a railcar cleaning composition which would be successful in the present invention, the Parco® 210 Cleaner was mixed with a volume of water that depended on the temperature of the cleaning. In a laboratory test with a cleaning temperature of 160-170 ° F, a solution of 20-25 vol. percentage of the Parco® 210 Water Cleaner, that is, 10-15 vol. percentage of phosphoric acid 0.2-0.25 vol. of sulfuric acid percentage, produced exemplary results. In a commercial test with a temperature of about 140 ° F, steel wool was included in a solution of 30-40 vol. percentage of the Parco® 21 Cleaner in water, that is, 18-25 vol. percentage of phosphoric acid 0.3-0.5 vol. percentage of sulfuric acid, which also produced good results. Through experimentation it has also been discovered that a combination of approximately 0.3 weight / volume percentage of Fe, 34.5 vol. of phosphoric acid percentage and 0.5 vol. of percent sulfuric acid and water, having a pH of about 1.3, gives particularly good results.

It was also discovered that iron exchangers, which are commonly used in iron phosphatization systems, were useful. These exchangers can be used when a certain amount of iron is needed in a solution. Excessive iron is removed by means of an iron exchanger. The iron exchanger generally has a size for the particular type of part that is receiving the treatment.

As used herein, the term "Phosphoric acid" includes orthophosphoric acid or any condensed phosphoric acid, such as, for example, pyrophosphoric acid or tripolyphosphoric acid, provided that the ratio of H20 / P2O5 is greater than 0 and not more than 3. "Total acidity is defined as The total of all forms of acidity in a solution, including mineral acidity, carbon dioxide, acid salts, and total acidity ("AT") can be measured in "points", which are defined for the purposes of this description as equivalent to the volume of a solution of 0.1 N sodium hydroxide, in millimeters, which would be required to titrate a 10 ml sample at a pH of 8.2 (as indicated, eg, by means of a phenolphthalein indicator).

As a non-limiting example of a conversion coating useful in the present process, it was found convenient to have a composition that includes 3-5 percent iron phosphate and 0.4-0.8 percent phosphoric acid in water. This composition is conveniently formulated by mixing an adequate amount of water with Bonderite® 1030, which was also supplied by Henkel Surface Technologies. Bonderite® 103 contains 3-5 percent iron phosphate, 1-10 vol. d percentage of phosphoric acid (Chem. Abstracts No. 07664-38-2), 10 vol. of percentage of sodium nitrate (Chem. Abstracts N 07631-99-4), 10-30 vol. of percentage of sodium chlorate (Chem Abstracts No. 0775-09-9), and other components. According to this, the composition of the present invention was obtained in an example by preparing a 4 vol solution. of Bonderite® 1030 e water, which provided good results.

According to the invention, the cleaning and phosphatization steps d are each followed by at least one rinsing step. Thus, according to the present invention, the conversion coating and acid cleaning compositions are applied by means of a process that includes, in order: medium acid spray cleaning with a solution including phosphoric acid rinsing by subsequent spraying to cleaning, spraying d * phosphate with a solution that includes a phosphate, and a rinse after the phosphate spray. This does not exclude the inclusion of additional intermediate stages, such as, for example, additional rinsing steps. In addition, people skilled in the art may appreciate that subsequent benefit can be obtained by including additional steps for auxiliary treatment such as sealing. In some cases, according to the invention, chromium-free rust inhibition sealants were used to seal the coatings of the metal surfaces.

In order to achieve a high-quality cleaning and coating, while preventing cross-contamination of the liquid to the nearby stages in which the liquid is also applied, the inventor has discovered that it is convenient to substantially contain the spray, aerosol and vapors of each stage so that they do not move to each of the other stages. In this way, the invention preferably includes the use of air barriers through which the articles are transported. These air barriers may include silhouettes of air blades, aerosols containing water, or a combination of any of these with each other or with other air barriers. For example, in a preferred embodiment, it is projected that the liquid may be drained from the articles after a spray application and before the application of the liquid in a subsequent step. As a limiting example, a period of time may be provided during which the spraying ends and the liquid is allowed to drain from the articles. This draining time can be provided by interrupting a conveyor, locating the next stage and / or air barriers such as the silhouettes, at a sufficient distance from the last spray nozzle or elevator, for example at 1-15 feet for Allow the liquid to drain during a time when substantial amounts of liquid are not applied. It was discovered that the higher spray pressures require the larger measurements to prevent dew, aerosol and vapors from each stage from being transferred to one of the other stages. For example, above 1,000 psig, he discovered that it was convenient to use silhouettes that were almost level against the articles. The edges of these silhouette had rubber to avoid damaging the items under treatment. In a preferred form of treatment of rail cart articles, the articles can be transported along rails, by spraying the items as they move along the stretches and through the air barriers. .

Although some recent efforts of other people have focused on cleaning compositions and methods requiring a spray at pressures of up to 2200-230 psig, the process according to the invention does not require this high pressure, and a cleaning is obtained superior always when there is sufficient drying time. It has been found that a drying time of 4-8 minutes at any pressure of about 18 to about 30 psig measured in upward sense of the spray nozzle (defined herein as "the acid spray pressure") provides superior results. . It has been found that a 1-minute drying time at any acid spray pressure from about 5 to about 70 psig is convenient while adequate results can be obtained at any moderate pressure. In addition, it has been discovered that under the above conditions, a treatment and coating superior to a moderate pH is obtained. For example, the cleaning step of the operation can be carried out at a pH of 1.2 1.8, although a pH of about 1.5 is preferred.

It has been discovered that a drying time for phosphate spraying of 2-4 minutes at any pressure from about 5 to about 60 psig measured in upward direction of the spray nozzle ((defined herein as "the spray pressure of the "phosphate") provides superior results.It has been found that a 1-minute drying time at any phosphate spray pressure of about 5 psig to about 70 psig is convenient, while adequate results can be obtained at any moderate pressure.

The iron phosphate composition should be applied in an amount such as to provide a coating thickness of at least 50 mg / square feet, and preferably in the range of 75 to 500 mg / square feet. The thickness of the most preferred coating is in the range of 75-150 mg / square feet. The thickness of the coating can be measured by weighing a small sample article, usually no larger than 1 square inch of area, before and after coating. The thickness of the coating is calculated by dividing the difference in weight between the area of the coated article.

Efficiency and quality are improved by carrying out the cleaning stage and the conversion stage at high temperatures. It has been found that maintaining a temperature of 120-200 ° F upstream of the acid spray nozzle (defined herein as "the acid spraying temperature") is convenient for the cleaning step, and it is preferable temperature of 140-170 ° F while maintaining a temperature of 80-150 ° F in ascending sense of the phosphate spraying nozzle (defined herein as "the phosphate spraying temperature") and convenient for coating application of phosphate, and a temperature of 120-130 ° F is preferable.

For the stages of phosphatization and chemical cleaning, it has been found to be convenient to use 10-1 elevators with spray nozzles at a distance of 10-1 inches, and nozzles at approximately 6-20 inches of the part. For the rinsing stages, it has been found that the same configuration using 10-15 elevators is convenient. It is estimated that a flow volume of approximately 1,000-3,000 gal / minute is desirable during the d cleaning and phosphatization steps, while 5-800 gal / minute and convenient during the rinse stages.

In a preferred embodiment, the articles are dried and / or cured for 3-30 minutes at 200-600 ° F, depending on the article being processed. For items of rail carts and barges, drying and / or curing preferably takes place at 200 to 400 ° F. For LP tank items, drying and / or curing is preferably carried out at 300 to 600 ° F. It has been found that gas-activated transmission ovens are suitable for these purposes.

After the articles are coated by conversion, they can be painted. The inventor achieved excellent results after coating test panels with two component systems that include epoxy or urethane co-based solvent or water. The term "two components" refers to mixing two separate components together before use to initiate a cross-linking reaction. These coatings are also designated with the term "d packages" or the prefix "2K" ("K" comes from the German word, Komponent). Epoxies and polyurethanes are the most common 2K coatings, where polyisocyanates serve as a cross-linking agent for polyurethanes. Urethanes exhibit excellent resistance to attack by solvents, lubricants, oils and other chemicals. They also achieved good results using polyester coatings such as polyethylene triglycidyl isocyanurate powder (TGIC).

Although impressive results were achieved without employing the known surface preparation methods described in the background of this application, the new method described herein may be conveniently combined with the known methods mentioned, including mechanical cleaning methods. For example, a significant advantage can be obtained by combining the described method with jet cleaning, cleaning electric tools, washing with water and abrasive injection in water.

EXAMPLES Two groups of articles of hot-rolled steel were tested. The first was a group of liquid petroleum (LP) tanks each with a surface area of approximately 30 square feet. The second was a group of panels and parts manufactured to simulate the configuration of rail cars.

Excellent results were achieved in a simulated commercial trial that included seven stages. At each stage, the treatments were applied by spray or spray at a pressure lower than 20 psig.

In the first stage, the steel test items were cleaned at 135-145 ° F with a solution that throughout several tests varied in concentration in the range of 25-3 vol. % of the Parco® 210 Cleaner in water. The spray pressure of the acid was maintained at approximately 10-15 psig. The articles were cleaned for a period ranging from 15 seconds to 6 minutes. It was observed that the longer cleaning periods offered improved results. Throughout the tests, it was also observed that an increase in the content of iron improved the efficiency of the elimination of lamination and welding scale casings. The iron content was subsequently increased by immersing a steel test piece in the cleaning solution for a time ranging from 30 minutes to overnight, and / or adding the steel directly to the cleaning solution. The tests started with an iron content of approximately 0.1 0.20 weight / vol. of percentage, and concluded with an iron content of approximately 0.30-0.35 weight / vol. of percentage.

A surprising amount of heavy black soot was observed in the liquid dripping areas of the test articles exposed only to the spray of the acid cleaning solution. It was assumed that the drying time was more important than the physical force with which jet stream of liquid was applied to the surface. It was discovered that a line speed of less than 2 feet / minute, which ensured a drying time of at least 4 minutes of cleaning, provided excellent results.

The completion of the cleaning stage included a period of time for draining. This period varied from 1 seconds to several minutes. Longer draining times had the advantage of helping to limit the acidity of Stage 2.

The cleaning step was followed by a rinse step with water that included two steps (step 2A and step 2B) in which pressures measured upstream of the nozzle were maintained at pressures ranging from 5 to 15 psig and temperatures They varied from 70 to 85 ° F. The completion of the second step of rinsing with water included a period of time for draining. It seems that approximately 100 seconds was a sufficient draining period. The pH of the rinse step was determined in a range of 3.6 to 6.5, where the first pass exhibited a lower pH than the second. A drain trough between Stage 1 and Stage 2 conveniently aided in reducing the pH decrease in Stage 2.

In the fourth stage, an iron phosphate conversion coating was applied which included 4.0 vol. d percentage of Bonderite® 1030 in water, at 9-10 points ("pts.") d total acidity, at a pressure of approximately 5 psig and at a temperature of 90-100 ° F. The completion of the conversion coating stage included a period of approximately 100 seconds for draining.

The conversion coating stage was followed by two separate rinsing steps. In the first rinse stage, it was found to be convenient to add or neutralize the acid to raise the pH to more than 7.5, thus reducing the instantaneous oxidation. For this purpose, a solution was selected that included approximately 15-20 vol. of percentage of sodium hydroxide in water, as e Neutralizer 700, available from Henkel Surface Technologies. The temperature in this stage was within the range of 70-90 ° F.

Finally, in the seventh and last stage, s applied a solution of 0.5-1.5 vol. of percentage (11.5 pts.) of chromium-free chemical seal Parcolene® 95 AT to avoid instantaneous oxidation. This type of chemical sealants can include a wide range of organic or inorganic sealants, powder or liquids. Inorganic sealers are preferred for electrical coatings, while you can use any type of sealant for liquid coatings.

In the cleaning and coating stages of the initial test runs, degassing problems of the coating were encountered, because certain areas of the test items had not been cleaned while other areas had been firmly coated with phosphate. The problems were corrected by the installation of rotating conveyors to rotate the tanks in Stage 1 and by the installation of additional elevators with nozzle to improve the spray patterns.

The rotating conveyors cause the tanks to rotate approximately 10.12 times in the stage. In addition there were originally 8 elevators (elevators) in the 12-inch centers in Stage 1. Three elevators were added to each side of the stage with jet nozzles "v" located in l elevators in the 6-inch centers.

Claims (61)

R E I V I N D I C A C I O N S

1. A process to treat a rail car article that includes hot rolled steel, where the process includes: cleaning by acid spraying the article c a solution including phosphoric acid, apply a subsequent rinse to the cleaning to article, phosphate the article with a solution that includes a phosphate, and apply a subsequent rinse to the phosphatizacid to the article.

2. The process, as claimed in clause 1, characterized in that it also includes that the aerosol mist and vapors of each stage are substantially contained so as not to be transferred to the other stages.

3. The process, as claimed in clause 2, characterized in that an air barrier is used to substantially contain the spray, aerosol and vapors of the stage so as not to be transferred to the other stages.

4. The process, as claimed in clause 1, characterized in that the article is sprayed for 1-minutes in the phosphate spraying step.

5. The process, as claimed in clause 1, characterized in that the article is sprayed during 2-minutes in the phosphate spraying step.

6. The process, as claimed in clause 1, characterized in that the spray pressure of the acid is 5-70 psig.

7. The process, as claimed in clause 1, characterized in that the spray pressure of the acid is 18-30 psig.

8. The process, as claimed in clause 1, characterized in that the phosphate spray pressure is 5-70 psig.

9. The process, as claimed in clause 1, characterized in that the phosphate spray pressure is 5-60 psig.

10. The process, as claimed in clause 1, characterized in that the article is rotated at least partially during at least a part of the process.

11. A process to treat a rail car article that includes hot rolled steel, where the process includes: clean by spraying the article for 4-8 minutes with a solution that includes phosphoric acid apply a subsequent rinse to the cleaning to article, phosphate the article for 1-6 minutes with a solution that includes a phosphate, and Apply a subsequent rinse to the phosphatization to the article.

12. The process, as claimed in clause 11, characterized in that it also includes that the aerosol spray and vapors of each stage are contained substantially so as not to be transferred to the other stages.

13. The process, as claimed in clause 11, characterized in that an ai barrier is used to substantially contain the spray, aerosol and vapors of the stage so as not to be transferred to the other stages.

14. The process, as claimed in clause 11, characterized in that the liquid is drained from the article after a spraying application and before liquid application in a subsequent step.

15. The process, as claimed in clause 11, characterized in that the phosphate is sprayed to provide a thickness of the article phosphate coating of at least 50 mg / square feet upon drying.

16. The process, as claimed in clause 11, characterized in that the phosphate is sprayed to provide a thickness of the article phosphate coating of 75-500 mg / square feet upon drying.

17. The process, as claimed in clause 11, characterized in that the phosphate is sprayed to provide a thickness of the phosphate coating in the article of 75-150 mg / square feet upon drying.

18. The process, as claimed in clause 11, characterized in that the temperature of the acid spray is 120-200 ° F.

19. The process, as claimed in clause 11, characterized in that the temperature of the acid spray is 140-170 ° F.

20. The process, as claimed in clause 11, characterized in that the temperature of the phosphate spray is 80-150 ° F.

21. The process, as claimed in clause 11, characterized in that the temperature of the phosphate d spray is 120-130 ° F.

22. The process, as claimed in clause 11, characterized in that the article is rotated at least partially during at least a part of the process.

23. A process to treat a railcar articul that includes hot rolled steel, where the process includes: clean by spraying the article for 4-8 minutes with a solution that includes phosphoric acid apply a rinse by spraying after cleaning the article, phosphate the article for 2-4 minutes with a solution that includes a phosphate, apply a rinse by subsequent spraying the phosphatization to the article, and Dry and / or cure the item at 200-400 ° F.

24. The process, as claimed in clause 23, characterized in that it also includes that the spray, aerosol and vapors of each stage are substantially contained so as not to be transferred to the other stages.

25. The process, as claimed in clause 23, characterized in that an air barrier is used to substantially contain the dew, aerosol and vapors of each stage so as not to be transferred to the other stages.

26. The process, as claimed in clause 23, characterized in that the phosphate is sprayed to provide a thickness of the phosphate coating in the article of at least 50 mg / square feet upon drying.

27. The process, as claimed in clause 23, characterized in that the phosphate is sprayed to provide a thickness of the phosphate coating in the article of 75-500 mg / square feet upon drying.

28. The process, as claimed in clause 23, characterized in that the phosphate is sprayed to provide a thickness of the phosphate coating in the article of 75-150 mg / square feet upon drying.

29. A process for treating a rail car article that includes hot-rolled steel, where the process includes: acid-spraying the article for 4-8 minutes with a solution that includes phosphoric acid apply a rinse by spraying after cleaning the article, phosphate the article for 2-4 minutes with a solution that includes a phosphate, and apply a rinse by spraying the phosphatization back to the article.

30. The process, as claimed in clause 29, characterized in that it also includes that the aerosol spray and vapors of each stage are substantially contained so as not to be transferred to the other stages.

31. The process, as claimed in clause 29, characterized in that an air barrier is used to substantially contain the dew, aerosol and vapors of each stage so as not to be transferred to the other stages.

32. The process, as claimed in clause 31, characterized in that the air barrier included some silhouettes.

33. The process, as claimed in clause 31, characterized in that the air barrier includes an air knife.

34. The process, as claimed in clause 31, characterized in that the air barrier includes or aerosol containing water.

35. The process, as claimed in clause 29, characterized in that the acid is sprayed at a flow volume of approximately 1,000-3,000 gal / minute.

36. The process, as claimed in clause 29, characterized in that the phosphate is sprayed at a flow volume of approximately 1,000-3,000 gal / minute.

37. The process, as claimed in clause 29, characterized in that the article is transported along rails lengths and the aerosol is applied to the article as the article moves along the sections, and where the spray, the aerosol and the vapors of each stage are substantially contained so as not to be transferred to the other stages, by means of air barriers located along the sections, through which the articles are transported.

38. The process, as claimed in clause 29, characterized in that the spray rinse after cleaning is sprayed at a flow volume of about 5-800 gal / minute.

39. The process, as claimed in clause 29, characterized in that the spray rinse after phosphatization is sprayed at a flow volume of about 5-800 gal / minute.

40. The process, as claimed in clause 29, characterized in that it also includes the application of a chemical sealant to the article.

41. A process to treat an article that includes hot rolled steel, where the process includes: clean by spraying the article for 1-8 minutes with a solution that includes phosphoric acid, apply a subsequent rinse to the article to clean, phosphate the article with a solution that includes a phosphate, and Apply a subsequent rinse to the phosphatization to the article.

42. The process, as claimed in clause 41, characterized in that the article includes an article of rail cars.

43. The process, as claimed in clause 41, characterized in that the article includes an article of an LP tank.

44. The process, as claimed in clause 41, characterized in that the article includes an article of a barge.

45. The process, as claimed in clause 41, characterized by including further, after application of the rinse by spraying after phosphatization, drying and / or curing of the article at 200-600 ° F.

46. The process, as claimed in clause 41, characterized in that the spray, aerosol and vapors of each stage are contained substantially so as not to pass through each of the other stages.

47. The process, as claimed in clause 41, characterized in that the article is sprayed for 1.6 minutes during the phosphate spraying step.

48. The process, as claimed in clause 41, characterized in that the liquid is drained from the article after a spraying application and before application of liquid in a subsequent step.

49. The process, as claimed in clause 41, characterized in that the article is sprayed during 2 4 minutes during the phosphate spraying step.

50. The process, as claimed in clause 41, characterized in that the article is rotated at least partially during at least a part of the process.

51. A process to treat an article of an LP tank that includes hot rolled steel, where the process includes: cleaning by spraying the article with acid for 4-8 minutes with a solution that includes phosphoric acid apply a rinse by spraying after cleaning the article, phosphate the article for 2-4 minutes with a solution that includes a phosphate, apply a rinse by subsequent spraying the phosphatization to the article, and Dry and / or cure the item at 300-600 ° F.

52. The process, as claimed in clause 51, characterized in that it also includes that the spray mist and vapors of each stage are contained substantially so as not to be transferred to the other stages.

53. The process, as claimed in clause 51, characterized in that an air barrier is used to substantially contain the dew, aerosol and vapors of each stage so as not to be transferred to the other stages.

54. The process, as claimed in clause 53, characterized in that the air barrier includes a silhouette.

55. The process, as claimed in clause 53, characterized in that the air barrier includes an air knife.

56. The process, as claimed in clause 53, characterized in that the air barrier includes an aerosol containing water.

57. The process, as claimed in clause 51, characterized in that the acid is sprayed at a flow volume of approximately 1,000-3,000 gal / minute.

58. The process, as claimed in clause 57, characterized in that the volume of flow passes through approximately 10-15 elevators that have spray nozzles at a distance of approximately 10-15 inches, where the nozzles are located approximately at 6 20 in. Away from the item.

59. The process, as claimed in clause 51, characterized in that the phosphate is sprayed at a flow volume of approximately 1,000-3,000 gal / minute.

60. The process, as claimed in clause 59, characterized in that the volume of flow passes through approximately 10-15 elevators that have a spray nozzle at a distance of approximately 10-15 inches, where the nozzles are located approximately 6- 20 in. Away from the item.

61. The process, as claimed in clause 51, characterized in that the article is rotated at least partially during at least a part of the process. SUMMARY A process is presented in which hot-rolled steel items, such as rail cart articles, LP tanks and barges, are cleaned and coated by conversion. Cleaning compositions include aqueous phosphoric acid, and conversion coating compositions include aqueous phosphate.