1、NACE International Item No. 24231 NACE International Publication 43107 This Technical Committee Report has been prepared by NACE International Task Group 066* on The Application of Solvent-Free Coatings to Railcars Using Plural-Component Spray Equipment. The Application of Solvent-Free Coatings to R
2、ailcars Using Plural-Component Spray Equipment January 2007, NACE International This NACE International technical committee report represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclude anyone fro
3、m manufacturing, marketing, purchasing, or using products, processes, or procedures not included in this report. Nothing contained in this NACE report is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or prod
4、uct covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent. This report should in no way be interpreted as a restriction on the use of better procedures or materials not discussed herein. Neither is this report intended to apply in all
5、 cases relating to the subject. Unpredictable circumstances may negate the usefulness of this report in specific instances. NACE assumes no responsibility for the interpretation or use of this report by other parties. Users of this NACE report are responsible for reviewing appropriate health, safety
6、, environmental, and regulatory documents and for determining their applicability in relation to this report prior to its use. This NACE report may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operat
7、ions detailed or referred to within this report. Users of this NACE report are also responsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicabl
8、e regulatory requirements prior to the use of this report. CAUTIONARY NOTICE: The user is cautioned to obtain the latest edition of this report. NACE reports are subject to periodic review, and may be revised or withdrawn at any time without prior notice. NACE reports are automatically withdrawn if
9、more than 10 years old. Purchasers of NACE reports may receive current information on all NACE International publications by contacting the NACE FirstService Department, 1440 South Creek Drive, Houston, Texas 77084-4906 (telephone +1 281/228-6200). Foreword This state-of-the-art report reviews the c
10、urrent information available concerning solvent-free coatings, their application to railcars, and the use of plural-component spray equipment. It is not intended as an all-encompassing technical document, but as an overview of the general trends and a description of the current generic products and
11、equipment involved. This report is written to assist coating and lining applicators in railcar shops. This technical committee report was prepared by NACE International Task Group (TG) 066, The Application of Solvent-Free Coating to Railcars Using Plural-Component Spray Equipment. This TG is adminis
12、tered by Specific Technology Group (STG) 43 on Land Transportation. It is also sponsored by STG 03 on Protective Coatings and LiningsImmersion/Buried. This technical committee report is issued by NACE International under the auspices of STG 43. _ *Chair Carl Sabo, The Sherwin Williams Company, Stron
13、gsville, Ohio.NACE International 2 Background Increasing environmental concerns and regulations in the United States have resulted in many new restrictions, regulations, and challenges that have dramatically affected the coating and lining of railcars. Coating formulations, production, and applicati
14、ons have been affected.Regulations have severely restricted the use of solvents, heavy metal pigments, and additives, and have emphasized safety of application. As a result of emission standards, there is increasing interest in the areas of water-borne and solvent-free systems. Definitions Flow Out:
15、 The ability of a coating to move over a substrate. Orange Peel: The dimpled appearance of a dried coating resembling the surface of an orange. Porosity: Film that is not dense or has small voids or holes. Pot Life: The elapsed time within which a coating can be effectively applied after all compone
16、nts of the coating have been thoroughly mixed. Coatings Trends Stimulated by environmental concerns, the coatings industry has been striving to develop practical solvent-free coatings and linings that meet or exceed environmental regulations with performance equal or superior to conventional coating
17、s. Solvent-free coating systems are now available in commercially acceptable form. These products often use heat rather than solvents to reduce viscosity. The cost of the solvent and its disposal are reduced. Solvent-Free Systems Previously, solvent-free epoxy, polyurethane, or polyurea coatings had
18、 not been widely used because there was no compelling motivation to switch from readily available solvent-containing coatings. Continuing focus on volatile organic compounds (VOC) reduction has resulted in the development and improvement of solvent-free coatings to equal the performance, appearance,
19、 and application properties of high-solids and 100%-solids coatings and linings. Formulating chemists have been able to achieve this objective by selecting lower-viscosity combinations of resins and curing agents. This has resulted in coatings that have been formulated to produce a finish ranging fr
20、om flat to high gloss. Because solvent-free coatings produce dense coating films, they have wearing properties at least comparable to solvent-based coatings. Solvent-free coatings are often applied as a single-coat direct-to-metal application that typically ranges from 254 to 508 m (10 to 20 mil). S
21、ome are also applied in multiple coats. Because of the typical short working pot life of the mixed products (from seconds to one hour), the products are applied using plural-component spray equipment in which the components are mixed in a manifold or in the spray gun itself. The components often are
22、 heated to reduce and control viscosity, which improves flow, and to achieve proper atomization, fluid transfer, and proportioning, as well as improve flow out in the coating system. Formulations frequently exhibit excellent application characteristics of improved edge protection and reduced holiday
23、s. Plural-Component Spray Equipment Plural-component spray technology has been used in the coatings industry for many years. It is a method of coating application in which two or more components are mixed and proportioned automatically by the spray equipment (see Figure 1). Although plural-component
24、 equipment has been used primarily for heavy-film applications (e.g., mastics, vinyl esters, or elastomerics of 762+ m (30+ mil), the equipment has been adapted for thin-film coatings 127 to 508 m (5 to 20 mil). NACE technical committee reports are intended to convey technical information or state-o
25、f-the-art knowledge regarding corrosion. In many cases, they discuss specific applications of corrosion mitigation technology, whether considered successful or not. Statements used to convey this information are factual and are provided to the reader as input and guidance for consideration when appl
26、ying this technology in the future. However, these statements are not intended to be recommendations for general application of this technology, and must not be construed as such. NACE International 3 FIGURE 1: Typical Fixed-Ratio Plural-Component Spray Equipment To prevent the mixed material from s
27、etting too quickly, becoming unusable, and hardening in the spray lines, the components are typically mixed at the spray gun or at a manifold preceding the spray gun. The mixed components are then sprayed immediately onto the substrate being coated. Mechanical plural-component spray units are of two
28、 basic typesfixed ratio and variable ratio. The fixed-ratio system provides only a set mixing ratio of the coating components such as 1:1, 2:1, 3:1, or 4:1. The system is sometimes retrofitted for other ratios, using available cylinders. A variable-ratio system can be adjusted for different componen
29、t ratios from 1:1 to 40:1. Variable-ratio equipment is available today that uses two independent pumps with metering valves that can be adjusted from 1:1 to 10:1 from a control panel. Plural-component spray equipment is typically equipped with explosion-proof electrical components as regulated by lo
30、cal or other authorities because solvents are still used for cleanup. Heated Coatings With Plural UnitsPlural-component spray equipment with heaters (see Figure 1) is typically used for the application of solvent-free coatings. Heating the coating rather than using solvents controls the viscosity an
31、d therefore the sprayability of the coating. A typical plural-component spray unit for spraying solvent-free coatings consists of an airless pump unit with lower units whose relative displacements are representative of the mixing ratio of the product being applied. Two components are delivered to th
32、e gun(s) or mix manifold through separate hoses, at which point they are combined and sprayed onto the substrate. Mixed materials are not generally run through a fluid heater. Multiple guns are sometimes attached to the mix manifold for faster application of the materials. NACE International 4 Separ
33、ate drum heaters, preheaters, insulated fluid lines, or heated fluid lines are typically used during the application. Because of the short working pot life of most solvent-free coatings, the plural-component spray unit has a separate solvent supply and pump for flushing and purging the equipment and
34、 spray lines. Impingement mix guns that use either air or mechanical purge also are available. How Mechanical Proportioning Works Two or more pumps or pressure tanks supply a simultaneous flow of fluid to the proportioner. Mechanical proportioners use two or more displacement pumps to measure the co
35、mponent chemicals. The pump strokes are synchronized by a mechanical connection. As the pumps operate, they proportion out component chemicals in ratios determined by the displacement of the pumps. Fluid is directed from the pumps to a mixing mechanism, then applied to the end product. Qualified Plu
36、ral-Component Equipment Technicians Proper operation and maintenance of the plural-component spray equipment is critical for a quality coating application. Some rail shops have designated and trained equipment technicians who have full responsibility for the maintenance and operation of the plural-c
37、omponent equipment. In some cases, the shops, in conjunction with spray equipment and coatings manufacturers whose products are being sprayed, have issued documents stating that those technicians are “Qualified.” Advantages of Solvent-Free Coatings with Plural-Component Applications The following ar
38、e advantages of solvent-free coatings: Improved edge coverage and flow characteristics Reduced solvent use and emissions Eliminated operator measuring and mixing variables Potential for reduced waste disposal with plural-component spray equipment Elimination of solvent odor Possible reduction of app
39、earance anomalies and nonconformances Reduced film porosity Controlled coating material temperature produces consistent spraying qualities in varying atmospheric and environmental conditions Material loss is limited to mixed material in spray lines between the mixing manifold and the spray gun Solve
40、nt use is greatly reduced because it is only used for flushing from the manifold to the gun (see Tables 1 and 2) NACE International 5 TABLE 1: Coating Characteristics During Application Railcar Exterior (88,900 L 23,500 gal Tank Car) Estimated Product Comparison (288 m2 3,100 ft2)(A) Alkyd Enamel Hi
41、gh-Solids Coating Solvent-Free Coating Solids by volume 55% 75% 100% VOC 335 to 397 g/L 249 g/L 0 to 36 g/L (2.8 to 3.3 lb/gal) (2.1 lb/gal) (0.2 to 0.3 lb/gal) Dry Temperature 66C (150F) 93C (200F) 93C (200F) Resistance Spread Rate 4.3 m2/L at 127 m 5.9 m2/L at 127 m 7.9 m2/L at 127 m(176 ft2/gal a
42、t 5 mil) (240 ft2/gal at 5 mil) (321 ft2/gal at 5 mil) Number of Coats 1 to 2 coats 1 coat 1 coat Ratio not applicable 1:1 1:1 Thinning Solvent 10% 10% None Average VOC per Car 41 kg (90 lb) 18 kg (40 lb) 1.6 kg (3.5 lb) Average Use per Car 91 to 114 L (24 to 30 gal) 68 to 76 L (18 to 20 gal) 38 to
43、53 L (10 to 14 gal) (A) Assume a 25% loss factor based on the use of plural-component spray equipment. Product comparison shown is for typical products. Assume a 30% loss factor based on the use of conventional or airless spray equipment. TABLE 2: Estimated Waste Disposal Comparison(A) Other Coating
44、sSolvent-Free Coatings Drum waste generated for disposal per year 120 drums 48 drums Cost per drum (average)$400 $400 Cost per year$48,000 $19,200 Disposal savings per year $28,800Freight savings per year (based on 10 drums per month and 160 km 100 miles transportation) $35 to $60 per drum x 72 drum
45、s (waste not generated) = $2,520 to $4,320Total savings per year$31,320 to $33,120(A) (A)1995 figures based on production shop with capacity to paint four to six railcars per day. Drum capacity = 208 L (55 gal). Cost figures are in U.S. dollars. NACE International 6 Advantages of Plural-Component Co
46、ating Applications The following are advantages of plural-component coating applications: Minimizes mixed material loss. The system mixes materials on demand, supplying only the amount of material desired. Very little disposal of mixed and hazardous material Hand mixing is minimal Mixes on demand, r
47、educing material and solvent waste Plural-component equipment can be set up to spray directly from 19-L (5-gal) cans, drums, or totes. Drums and totes might be reusable. Accurate ratio checking and proportioning Less solvent waste from cleaning equipment versus standard airless spray equipment Concl
48、usions With the changes in environmental regulations and their increased enforcement, particularly regarding VOC levels, the coating of railcars has been subjected to stringent compliance requirements. New field-proven solvent-free coatings and linings have been successfully formulated and used, sub
49、stantially reducing the use of solvents while meeting current and expected governmental regulations. Because of the short pot life of the mixed materials, plural-component spray equipment has been used to apply most solvent-free coatings. In most of these applications, heating the materials rather than using solvents controls the viscosity. This method improves flow, produces a continuous coating film, reduces orange-peel finishes, and improves weld/crevice penetration. Once the initial investment of
