1、Item No. 24191NACE International Publication 14C296This Technical Committee Report has been prepared byNACE International Task Group T-14C-4* on CoatingsUnder Insulation on RailcarsA State-of-the-Art Report on Protective Coatings forMitigating Corrosion Under Insulation on Rail Tank Cars July 1996,
2、NACE InternationalThis NACE International technical committee report represents a consensus of those individual memberswho have reviewed this document, its scope, and provisions. Its acceptance does not in any respect precludeanyone from manufacturing, marketing, purchasing, or using products, proce
3、sses, or procedures not included inthis report. Nothing contained in this NACE International report is to be construed as granting any right, byimplication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or productcovered by Letters Patent, or as indemnifying or
4、protecting anyone against liability for infringement of LettersPatent. This report should in no way be interpreted as a restriction on the use of better procedures or materialsnot discussed herein. Neither is this report intended to apply in all cases relating to the subject. Unpredictablecircumstan
5、ces may negate the usefulness of this report in specific instances. NACE International assumes noresponsibility for the interpretation or use of this report by other parties.Users of this NACE International report are responsible for reviewing appropriate health, safety,environmental, and regulatory
6、 documents and for determining their applicability in relation to this report prior to itsuse. This NACE International report may not necessarily address all potential health and safety problems orenvironmental hazards associated with the use of materials, equipment, and/or operations detailed or re
7、ferred towithin this report. Users of this NACE International report are also responsible for establishing appropriatehealth, safety, and environmental protection practices, in consultation with appropriate regulatory authorities ifnecessary, to achieve compliance with any existing applicable regula
8、tory requirements prior to the use of thisreport.CAUTIONARY NOTICE: The user is cautioned to obtain the latest edition of this report. NACEInternational reports are subject to periodic review, and may be revised or withdrawn at any time without priornotice. NACE reports are automatically withdrawn i
9、f more than 10 years old. Purchasers of NACE Internationalreports may receive current information on all NACE International publications by contacting the NACEInternational Membership Services Department, P.O. Box 218340, Houston, Texas 77218-8340 (telephone +1281/228-6200).ForewordThis NACE Interna
10、tional technical committee report hasbeen prepared for use by railcar owners and manu-facturers and outlines preventive measures that havebeen employed to mitigate corrosion under insulation onrail tank cars. NACE Publication 6H189, “A State-of-the-Art Report on Protective Coatings for Carbon Steel
11、andAustenitic Stainless Steel Surfaces Under Thermal Insu-lation and Cementitious Fireproofing,”1provides a guidefor design and selection of protective coatings for useunder insulation on stationary tanks. However, 6H189does not specifically address rail tank cars, for which theoperating conditions
12、may be significantly different.Most insulated tank cars employ a light-density fiber-glass insulation which, when coupled with any of avariety of light-duty coating systems with minimal or nosurface preparation, has had few or no reported cor-rosion problems. However, a survey of Unit CommitteeT-14C
13、 members and associates indicated that a sig-nificant percentage of the respondents were using spe-cialized insulation systems or were experiencing relative-ly extreme service conditions, resulting in corrosion ofthe tank and jacket. The consensus was that a state-of-the-art report was necessary to
14、address conditions spe-cific to rail tank cars.This technical committee report was prepared by NACEInternational Task Group T-14C-4, a component of UnitCommittee T-14C on Rail Equipment Corrosion, whichserves to promote the development of techniques toextend the service life of rail equipment. This
15、report isissued by NACE International under the auspices ofGroup Committee T-14 on Corrosion in the Transpor-tation Industry._*Chairman Al Hendricks, Wisconsin Protective Coatings, Green Bay, WI.NACE International2IntroductionCorrosion of stainless steel, carbon steel, and aluminumtakes place to var
16、ying degrees under thermal insulationin the presence of moisture. Water and/or steam mayenter the insulation space through penetration points inthe jacket, by capillary action (wicking) through oraround the insulating medium, or through damagedsteam coils. The presence of moisture can lead to gen-er
17、al corrosion, pitting, and/or cracking. Because theexterior surfaces of the tank car shell and the interiorsurfaces of the jacket are not normally inspected afterthe original construction, such corrosion may go un-detected for a great portion of the tank cars expected lifeunless the jacket is remove
18、d.The potential for significant corrosion under insulation onrail tank cars can be related to: operating temperature; constituents in the insulation that form corrosivesolutions when combined with moisture; the tendency of some insulation material to absorband/or retain moisture; the insulations lac
19、k of adhesion to the substrate;and contact with the commodity being transported.Corrosion was first detected under foam insulationapplied to tank cars in the 1960s. Some urethane foamswere found to have a propensity to release acids uponexposure to heat and moisture. Consequently, allinsulation syst
20、ems used on tank cars are now subject tocorrosion testing in accordance with AAR(1)SpecificationM-1002, Section 2.2.12.2This corrosion test is actuallydesigned for foam-in-place (FIP) urethane. In addition tocorrosion testing for the insulation system, Section2.2.12 requires that the exterior surfac
21、es of carbon steeltanks and the interior surfaces of carbon steel jackets begiven a protective coating.This state-of-the-art report describes types of insulationand coating systems used on tank cars to providecorrosion control. Temperature limitations are providedfor each system.Types of Insulation
22、MaterialsFollowing are descriptions of various types of insulationmaterials that have been used on tank cars. They arelisted in descending order based on frequency of use.Fiberglass: A light-density (1.4 to 3.5 lb/ft32.2 to 5.6kg/m3) glass fiber with an organic binding resin, a semi-rigid formed boa
23、rd, or a sheet (sheets are of variousdensities). Available with various types of factory-attached outer facings. Maximum service temperaturehas been 450F (232C). These materials have veryhigh water absorption, 93% by volume.Ceramic Fiber : A light- to medium-density (2.0 to 8.0lb/ft33.2 to 12.8 kg/m
24、3) spun or woven material com-posed of ceramic fibers. Maximum service temperaturehas been 3,200F (1,760C). These materials have ex-tremely high water absorption and are hygroscopic.Mineral Wool: A light- to medium-density (7.0 to 12lb/ft311.2 to 19.2 kg/m3) spun or woven (rock or glass)mineral fibe
25、r. Maximum service temperature has been400F (204C) for Class 1 and 1,800F (982C) for Class5. These materials have low to high water absorption,depending on the binder resin and service temperature.Urethane Foam: A light- to heavy-density (1.5 to 20lb/ft32.4 to 32 kg/m3) foam-in-place urethane create
26、dby the reaction of a polyol with an isocyanate. Maximumservice temperatures have varied from 250 to 450F(121 to 232C). Blowing agents and fire retardants in-cluded in FIP formulations can combine with moistureunder certain conditions to produce acidity. Water ab-sorption is low because of the close
27、d-cell structure; how-ever, when cells are broken, some wicking may occur.Urethane foam usually has excellent adhesion to steel,even with marginal preparation, but where adhesion isweak, the potential for moisture absorption is high.Cork: A medium- to heavy-density composite materialcomposed of frag
28、ments of cork tree bark and bindingresin. Maximum service temperatures have reached360F (182C). The materials have low water absorp-tion.Closed-Cell Rubber: A medium-density (4.5 to 8.5lb/ft37.2 to 14 kg/m3) composite material made ofsynthetic rubber. Maximum service temperatures havereached 220F (1
29、04C). These materials have low waterabsorption. Closed-cell rubber was formerly used oncold-service tank cars.Coating SystemsNumerous coating systems have been used to providecorrosion protection to insulated carbon steel, stainlesssteel, and aluminum rail cars. The selection of a coatingsystem is d
30、irectly related to the type of insulation, theanticipated temperature conditions, the commodity beingtransported, application limitations, economics, the ma-terial of construction, and the facilitys ability to apply acoating system that contains flammable or hazardousmaterials.The following coating
31、systems have been used undervarious types of insulation for periods of time extendingfrom 1 to 40 years. This alphabetical listing is not in-tended to imply any order of preference or use. _(1)Association of American Railroads (AAR), 50 F St. NW, Washington, DC 20001-1564.NACE International3Alkyd Pr
32、imers These coating systems have been exposed toservice conditions where substrate temperatures reach amaximum of 120F (48C) for continuous service andhave temporary excursions to 160F (71C). These systems have been applied in one coat to adry film thickness (DFT) of 1.5 to 3.0 mils (38 to 76 m). Th
33、ese systems have demonstrated moderate resis-tance to moisture, acids, and alkalies; their use has beenlimited under insulation that forms high concentrations ofacids or alkalies or harbors excessive condensation.Black Acrylic Rubber These coating systems have been exposed toservice conditions where
34、 substrate temperatures reach amaximum of 120F (48C) for continuous service andhave temporary excursions to 160F (71C). These systems have been applied in one coat to aDFT of 1.5 to 3.0 mils (38 to 76 m). These systems have demonstrated resistance toacids and alkalies, but their use has been limited
35、 underinsulation that forms high concentrations of acids oralkalies.Epoxy Amines These coating systems have been exposed toservice conditions where substrate temperatures reach amaximum of 250F (120C) for continuous service andhave temporary excursions to 350F (177C). These systems have been applied
36、 in two coats to atotal DFT of 8 to 12 mils (200 to 300 m). These systems have demonstrated good resistanceto acids and alkalies and have been suitable for use witha wide range of insulation materials. When these systems have been applied overstainless steel that is not abrasive blasted, the film th
37、ick-ness has been decreased to 4 to 6 mils (100 to 150 m).Epoxy Polyamides These coating systems have been exposed toservice conditions where substrate temperatures reach amaximum of 200F (93C) for continuous service andhave temporary excursions to 300F (148C). These systems have been applied in two
38、 coats to atotal DFT of 8 to 12 mils (200 to 300 m). Inhibitiveprimers have been used under some conditions. These systems have demonstrated good resistanceto acids and alkalies and have been suitable for use witha wide range of insulation materials. When these systems have been applied overstainles
39、s steel that is not abrasive blasted, the film thick-ness has been decreased to 4 to 6 mils (100 to 150 m).Modified Epoxy/Phenolics These coating systems have been exposed toservice conditions where substrate temperatures reach amaximum of 350F (177C) for continuous service andhave temporary excursi
40、ons to 450F (232C). These systems have been applied in two coats to atotal DFT of 8 to 12 mils (200 to 300 m). Inhibitiveprimers have been used under some conditions. These systems have demonstrated excellent resis-tance to acids and alkalies and have been suitable foruse with a wide range of insula
41、tion materials. When these systems have been applied overstainless steel that is not abrasive blasted, the film thick-ness has been decreased to 4 to 6 mils (100 to 150 m).Organic Zinc(2) These coating systems have been exposed toservice conditions where substrate temperatures reach amaximum of 140F
42、 (60C) for continuous service andhave temporary excursions to 300F (148C). These systems have been applied in one coat to aDFT of 1.5 to 3.0 mils (38 to 75 m). These systems have demonstrated moderate resis-tance to acids and alkalies, but their use has beenlimited under insulation that forms high c
43、oncentrations ofacids or alkalies. Organic zinc differs from inorganic zinc.Vinyl Acetate Emulsion Primer These coating systems have been exposed toservice conditions where substrate temperatures reach amaximum of 120F (48C) for continuous service andhave temporary excursions to 160F (71C). These sy
44、stems have been applied in one coat to aDFT of 0.75 to 1.0 mils (19 to 25 m). These systems have not demonstrated resistance toexcessively moist or chemical conditions.Waterborne Acrylic These coating systems have been exposed to ser-vice conditions where substrate temperatures reach amaximum of 120
45、F (48C) for continuous service andhave temporary excursions to 160F (71C). These systems have been applied in two coats to atotal DFT of 3.0 to 6.0 mils (75 to 150 m). These systems have demonstrated good resistanceto acids and alkalies, but their use has been limited un-der insulation that forms hi
46、gh concentrations of acids oralkalies.Waterborne Copolymeric Latex These coating systems have been exposed toservice conditions where substrate temperatures reach a_(2)Historically, inorganic zincs were used because of their excellent protection at extremely high temperatures; they were generally ca
47、pable ofresisting temperatures up to 700F (370C). However, its now known that inorganic zincs actually accelerate corrosion when exposed totemperatures of 140 to 250F (60 to 120C) under wet conditions. This phenomenon is attributed to a galvanic reversal of the zinc.NACE International4maximum of 120
48、F (48C) for continuous service andhave temporary excursions to 160F (71C). These systems have been applied in two coats to atotal DFT of 3.0 to 6.0 mils (75 to 150 m). These systems have demonstrated moderate re-sistance to acids and alkalies, but their use has beenlimited under insulation that form
49、s high concentrations ofacids or alkalies.Tests for Coating EvaluationA variety of test methods have been used for determin-ing the suitability of a coating system to protect surfacesunder insulation. Frequently, the test has been con-ducted under harsher conditions than the actual ex-posure in order to provide the user confidence for long-term service life. The severity of the test has dependedon
