1、Designation: A 755/A 755M 03Standard Specification forSteel Sheet, Metallic Coated by the Hot-Dip Process andPrepainted by the Coil-Coating Process for ExteriorExposed Building Products1This standard is issued under the fixed designation A 755/A 755M; the number immediately following the designation
2、 indicates the yearof original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agenc
3、ies of the Department of Defense.1. Scope*1.1 This specification covers steel sheet metallic coated bythe hot-dip process and coil-coated with organic films forexterior exposed building products. Sheet of this designation isfurnished in coils, cut lengths, and formed cut lengths. Build-ing products
4、include corrugated and various types of roll andbrake-formed configurations.1.2 The substrate is available in several different metallic-coated steel sheet products as enumerated in 4.1, depending onthe requirements of the purchaser.1.3 Coating systems supplied under this specification con-sist of a
5、 primer coat covered by various types and thicknessesof top coats. The combination of primer and top coat is classedas either a two-coat thin-film system or as a two-coat (or more)thick-film system. Typical top-coating materials are: polyester,silicone polyester, acrylic, fluoropolymer, plastisol, o
6、r polyure-thane.1.4 This specification is applicable to orders in eitherinch-pound units (as A 755) or SI units as A 755M. Values ininch-pound units and SI units are not necessarily equivalent.Within the text, SI units are shown in brackets. Each systemshall be used independently of each other.1.5 U
7、nless the order specifies the “M” designation (SI units)the product shall be furnished to inch-pound units.1.6 The text of this specification references notes andfootnotes that provide explanatory material. These notes andfootnotes, excluding those in tables and figures, shall not beconsidered as re
8、quirements of this specification.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitat
9、ions prior to use.2. Referenced Documents2.1 ASTM Standards:2A 463/A 463M Specification for Steel Sheet, Aluminum-Coated, by the Hot-Dip ProcessA 653/A 653M Specification for Steel Sheet, Zinc-Coated(Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed)by the Hot-Dip ProcessA 792/A 792M Specification
10、 for Steel Sheet, 55 %Aluminum-Zinc Alloy-Coated by the Hot-Dip ProcessA 875/A 875M Specification for Steel Sheet, Zinc-5 %Alu-minum Alloy Coated by the Hot-Dip ProcessA 902 Terminology Relating to Metallic Coated Steel Prod-uctsA 924/A 924M Specification for General Requirements forSteel Sheet, Met
11、allic-Coated by the Hot-Dip ProcessB 117 Practice for Operating Salt Spray (Fog) ApparatusD 522 Test Methods for Mandrel Bend Test of AttachedOrganic CoatingsD 523 Test Method for Specular GlossD 659 Method for Evaluating Degree of Chalking of Exte-rior Paints3D 714 Test Method for Evaluating Degree
12、 of Blistering ofPaintsD 822 Practice for Filtered Open-Flame Carbon-Arc Expo-sures of Paint and Related CoatingsD 870 Practice for Testing Water Resistance of CoatingsUsing Water ImmersionD 1005 Test Method for Measurement of Dry-Film Thick-ness of Organic Coatings Using MicrometersD 1654 Test Meth
13、od for Evaluation of Painted or CoatedSpecimens Subjected to Corrosive EnvironmentsD 1735 Practice for Testing Water Resistance of CoatingsUsing Water Fog Apparatus1This specification is under the jurisdiction of ASTM Committee A05 onMetallic-Coated Iron and Steel Products and is the direct responsi
14、bility ofSubcommittee A05.11 on Sheet Specifications.Current edition approved Oct. 1, 2003. Published December 2003. Originallyapproved in 1978. Last previous edition approved in 2001 as A 755/A 755M 01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Ser
15、vice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohoc
16、ken, PA 19428-2959, United States.D 2240 Test Method for Rubber PropertyDurometerHardnessD 2244 Practice for Calculation of Color Tolerances andColor Differences from Instrumentally Measured ColorCoordinatesD 2247 Practice for Testing Water Resistance of Coatings in100 % Relative HumidityD 2370 Test
17、 Method for Tensile Properties of OrganicCoatingsD 3359 Test Method for Measuring Adhesion by Tape TestD 3363 Test Method for Film Hardness by Pencil TestD 4145 Test Method for Coating Flexibility of PrepaintedSheetD 4214 Test Methods for Evaluating the Degree of Chalk-ing of Exterior Paint FilmsG 8
18、5 Practice for Modified Salt Spray Fog Testing3. Terminology3.1 Definitions:3.1.1 SubstrateFor definitions of terms relating to thesubstrate, see Terminology A 902.3.1.2 Coatings:3.1.2.1 acrylic, na polymer based on resins prepared froma combination of acrylic and methacrylic esters, acrylic andmeth
19、acrylic acids, and styrene; they contain one or morefunctional groups such as amide, hydroxy, or carboxy and formthermosetting systems on baking by cross-linking with them-selves, or amino or epoxy resins.3.1.2.2 conversion coating, na chemical treatment, nor-mally applied to a metal surface prior t
20、o final finishing, whichis designed to react with and modify the metal to produce asurface suitable for painting.3.1.2.3 epoxy, npolymers based on epoxy resins, whichare the reaction product of epichlorohydrin and biphenol-Aandare cross-linked with amino or urea-formaldehyde resins toform thermosett
21、ing systems on baking.3.1.2.4 fluorocarbon, npolymers based on fluorocarbonresins made by the polymerization of vinyl fluoride monomer(PVF) or vinylidene fluoride monomer (PVF2); these resins areformulated into coatings by dispersion of finely divided par-ticles in dispersants and diluents and form
22、thermosettingsystems on baking.3.1.2.5 plastisol, na dispersion of finely divided vinylresin in plasticizers; during the baking process, the resinparticles are solvated by the plasticizer and fuse into acontinuous film.3.1.2.6 polyester, na polymer based on the condensationproducts of polybasic acid
23、s and diols (dihydric alcohols), alsocalled oil-alkyds; they are modified by the addition reaction ofmonomers such as styrene or acrylic esters; polyester resins arecross-linked with amino resins to form thermosetting systemson baking.3.1.2.7 polyurethane, na polymer produced by the addi-tion reacti
24、on of an acrylic polyol or polyester polyol with anisocyanate-containing compound to produce thermosettingsystems on baking.3.1.2.8 primer, nthe first complete layer of paint of acoating system applied to an uncoated surface; the type ofprimer varies with the type of surface and its condition, thein
25、tended purpose, and the coating system being used.3.1.2.9 silicone polyester, na polymer which is the reac-tion product between an organo-siloxane intermediate and analkyd resin, or a cold blend of a silicone resin and a compatiblealkyd resin; these resins are cross-linked with amino resins toform t
26、hermosetting systems on baking.3.1.3 Coating Characteristics:3.1.3.1 chalking, vthe formation on a pigmented coatingof a friable powder evolved from the film itself at or justbeneath the surface.3.1.3.2 fade, va loss in color intensity experienced bypigmented organic coatings over time, generally du
27、e to theeffect of ultraviolet radiation.3.1.3.3 gloss, nthe luster, shininess, or reflecting ability ofa surface.3.2 Definitions of Terms Specific to This Standard:3.2.1 bottom side, nthe side of prepainted sheet oppositethe exposed weathering side.3.2.2 coil coating, va continuous process by which
28、paintand other coatings are applied and baked onto a moving stripof steel sheet.3.2.2.1 DiscussionRolls are used to pick up, meter, anddeposit the liquid coating onto the moving strip and are alsoused to support the strip through the line. The product of thisprocess is called prepainted steel sheet.
29、3.2.3 mil, na unit of length equal to 0.001 in. 25.4 m,used for describing the thickness of paint coatings.3.2.4 paint, n of coil coating, an organic liquid,pigmented/nonpigmented, which is converted to a solid film bybaking.3.2.5 roll former, nan apparatus that forms a continuousstrip of metal into
30、 various shapes by a series of contoured steelrolls.3.2.6 top side, nthe side of the prepainted sheet which isexposed to weathering.3.2.7 washcoat, na thin organic coating, usually a poly-ester, applied to the back or unexposed side of prepainted sheet(also known as a backercoat).3.2.7.1 DiscussionT
31、his pigmented/nonpigmented coatingis applied for such reasons as protection of the topcoat while incoil form, interior appearance, and lubrication during rollforming.4. Classification4.1 The substrate shall conform to all requirements of theappropriate specification for the steel sheet product order
32、ed asfollows:4.1.1 Zinc-Coated (Galvanized)Specification A 653/A 653M.4.1.2 Zinc-5 % Aluminum Alloy-CoatedSpecificationA 875/A 875M.4.1.3 55 % Aluminum-Zinc Alloy-CoatedSpecificationA 792/A 792M.4.1.4 Aluminum CoatedSpecification A 463/A 463M.4.1.5 Each of the above-listed metallic-coated sheet spec
33、i-fications describes the range of available coating designations.A 755/A 755M 032The particular designation selected is related to the expectedperformance of the exterior exposed building product. Al-though there are exceptions based on the type of environmentwhere the building is erected, the reco
34、mmended minimumcoating mass designations for use in exterior exposed buildingapplications are:Metallic Coating Minimum Recommended CoatingA 653/A 653M Zinc-Coated (Galvanized) G90 Z275A 875/A 875M Zinc-5 % Aluminum Alloy-Coated GF75 ZGF225A 792/A 792M 55 % Aluminum-Zinc Alloy-Coated AZ50 AZM150A 463
35、/A 463M Aluminum Coated T2 65 T2 200These minimum coating weight mass designations areimportant to attain the normally expected long-term productlife in the application. Exceptions to these minimum designa-tions can be considered when the environmental conditions areof low corrosive potential, such
36、as a very dry climate. In thesecases, a lower coating weight mass, for example, G60 Z180may be appropriate. Similarly, for very corrosive environ-ments, the user should consider specifying a coating designa-tion with a heavier coating weight mass.4.2 The organic coating typically consists of a prime
37、r and atopcoat on the top (exposed) side and washcoat on the bottom(unexposed) side. Typical primers and topcoats are as follows:4.2.1 Primers:4.2.1.1 Epoxy.4.2.1.2 Acrylic.4.2.1.3 Polyurethane.4.2.1.4 Polyester4.2.2 Top Coats:4.2.2.1 Polyester.4.2.2.2 Silicone polyester.4.2.2.3 Acrylic.4.2.2.4 Fluo
38、ropolymer.4.2.2.5 Plastisol.4.2.2.6 Polyurethane.4.2.3 Washcoats or Backercoats:4.2.3.1 Polyester.4.2.3.2 Acrylic.4.3 Other coatings will be specified if agreed upon betweenthe producer and the purchaser (see Note 2).5. Ordering Information5.1 The coated flat sheet covered by this specification ispr
39、oduced on continuous lines to decimal thickness only. Thethickness of the sheet includes the base steel and the metalliccoating. The thickness of the organic system is in addition tothe substrate (base steel and metallic coating).5.2 Orders for material under this specification shall includethe foll
40、owing information, as applicable, to describe therequired product adequately:5.2.1 Product name (prepainted steel sheet),5.2.2 ASTM designation and year of issue, as A 755 forinch-pound units or A 755M for SI units,5.2.3 ASTM specification number of metallic coated sub-strate, steel sheet designatio
41、n, and, if applicable, type (andgrade, if required),5.2.4 Metallic coating type (see 4.1),5.2.5 Metallic coating weight mass designation,5.2.6 Metallic coating finish (such as regular, minimizedspangle, extra smooth, or minimized spangle-extra smooth),5.2.7 Organic coating system designation (see 4.
42、2 or 4.3),5.2.8 Dry organic film thickness top side and bottom side(the top side will consist of a primer and topcoat and thebottom side will consist of a primer and a washcoat, or thesame coating as the topside) (see 7.4.2),5.2.9 Protection required (waxed or strippable coating),5.2.10 Dimensions (
43、thickness, width, either flat or formed(overall or cover) and length (if cut length) and, if applicable,type of formed configuration. The purchaser shall specify theappropriate table of thickness tolerances in SpecificationA 924/A 924M which applies to the order, that is, the table ofthickness toler
44、ances for38-in. 10-mm edge distance, or thetable of thickness tolerances for 1-in. 25- mm edge distance.5.2.11 Coil size requirement: maximum outside diameter,acceptable inside diameter, and maximum weight mass,5.2.12 Cut length requirement: maximum lift weight mass,5.2.13 Special requirements, if a
45、ny, and5.2.14 Application (part identification and description).NOTE 1A typical ordering description is as follows:Prepainted steel sheet, ASTM A 755 _ on zinc-coated (galvanized)substrate, ASTM A 653, SS, Grade 40 with G 90 coating, extra smooth,Top Side Primer, 0.25 mil thickness plus Gold Silicon
46、e-Polyester, 0.8 milthickness, Bottom Side Primer, 0.25 mil thickness plus Washcoat, 0.3 milthickness, 0.019 in. min thickness by 42 in. width by Coil, 24 in. insidediameter, 52 in. max outside diameter, 20 000 pound max weight coil forroll-formed exterior building siding.Prepainted steel sheet, AST
47、M A 755M _ on 55 % aluminum-zincalloy-coated substrate, ASTM A 792M, CS Type A with AZM150aluminum-zinc alloy coating, extra smooth, Top Side Primer, 0.006 mmthickness plus White Fluoropolymer, 0.020 mm thickness, Bottom SidePrimer, 0.006 mm thickness plus Washcoat, 0.008 mm thickness, 0.80 mmthickn
48、ess by 1000 mm width by Coil, 600 mm inside diameter, 1320 mmmax outside diameter, 4500 kg max coil for roll-formed exterior siding.NOTE 2When specifying the organic coating system designation,instead of using the generic terms listed in 4.2, it is permissible tosubstitute trade name terminology as
49、published by various coating andprepainted sheet suppliers. These trade name coatings are brand nameversions of the generic coatings listed in 4.2 and include a primer and filmthickness values.6. Substrate Requirements6.1 For the purposes of this specification, substrate refers tothe steel sheet and metallic coating. The specific requirementsfor the substrate are contained in the specifications listed in 4.1.7. Organic Coating Requirements7.1 The application of organic coatings on a continuous coilcoating lin
