1、 SURFACE VEHICLE RECOMMENDED PRACTICE J1562 APR2015 Issued 1999-12 Reaffirmed 2015-04 Superseding J1562 JAN2009 Selection of Zinc and Zinc-Alloy (Hot-Dipped and Electrodeposited) Coated Steel Sheet RATIONALE J1562 has been reaffirmed to comply with the SAE five-year review policy. _ SAE Technical St
2、andards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole
3、responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2015 SAE International All rights reserved. No part of this publication may be
4、reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-4970 (outside USA) Fa
5、x: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/J1562_201504 1. SCOPE Zinc and zinc-alloy coated steel is used to enhance a structures protection a
6、gainst corrosion degradation. For the purpose of this SAE Recommended Practice, a galvanized coating is defined as a zinc or zinc-alloy metallic coating. The selection of the optimum galvanized steel sheet product depends on many factors, the most important being: desired corrosion protection, forma
7、bility, weldability, surface characteristics, and paintability. The trade-offs of these product characteristics are more complex than is the case with uncoated steel sheet products. 1.1 Purpose This document defines preferred product characteristics. It also explains the various manufacturing proces
8、ses, presents the advantages and disadvantages of the resulting product characteristics, and discusses the trade-offs between corrosion protection properties and fabricating, assembling, and finish-coating process. 2. REFERENCES 2.1 Applicable Publications The following publications form a part of t
9、his specification to the extent specified herein. Unless otherwise indicated, the latest version of SAE publications shall apply. 2.1.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (out
10、side USA), www.sae.org. SAE J1392 Steel, High Strength, Hot Rolled Sheet and Strip, Cold Rolled Sheet, and Coated Sheet SAE J2329 Categorization and Properties of Low-Carbon Automotive Sheet Steels SAE J2340 Categorization and Properties of Dent Resistant, High Strength, and Ultra High Strength Auto
11、motive Sheet Steel SAE J2745 Categorization and Properties of Advanced High Strength Automotive Sheet Steels 2.1.2 ASTM Publications Available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, Tel: 610-832-9585, www.astm.org. ASTM A90/A90M Test Method f
12、or Weight (Mass) of Coating on Iron and Steel Articles with Zinc or Zinc-Alloy Coatings ASTM A653/A653M Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process ASTM A754/A754M Test Method for Coating Thickness by X-Ray Fluorescence ASTM
13、 A879/A879M Specification for Steel Sheet, Zinc Coated by the Electrolytic Process for Applications Requiring Designation of the Coating Mass on Each Surface ASTM A924/A924M General Requirements for Sheet Steel, Metallic Coated by Hot Dip Process 3. THE GALVANIZING PROCESS Two generic processes for
14、metallic coated steels are currently used in the automotive industry: (1) hot-dipped coating and (2) electrolytic coating. Coating line conditions can be adjusted to produce a variety of coating masses and coating compositions. 3.1 The Hot-Dip Process The uncoated coil product is usually annealed in
15、-line or in a separate furnace. The steel is then passed continuously through a molten metal bath. Upon emergence from the bath, the molten metal coating mass is controlled by air (or other gas) knives or mechanical wipers before the coating solidifies. This produces the commonly used two-side zinc-
16、coated sheet. 3.2 The Electrodeposition Process Electrolytic coating is done in a continuous coating process using cells in which the metals are electrodeposited on pre-annealed steel. Coating mass is controlled by the electrodeposition rate in the plating cells. This product is available in one or
17、two side coated sheet. 4. THE GALVANIZED COATING The galvanized coating is applied to the steel sheet prior to delivery to the fabricating plant. The coating remains substantially intact through subsequent forming, and painting operations. The coating provides both barrier and sacrificial protection
18、. 4.1 Composition of Coatings 4.1.1 Types of Coatings1Types of commercially produced coatings include: (1) zinc, (2) zinc-iron (20% iron) alloys, (3) aluminum-zinc silicon (55, 43, and 2 weight percent respectively) alloy, (4) zinc-aluminum (5% aluminum) alloy, and (5) zinc-nickel (20% nickel) alloy
19、. Coatings (1) and (2) can be applied by either electroplating or hot-dip coating. Coatings (3) and (4) are applied by hot-dip coating while coating (5) is applied by electroplating. 1All coating compositions included in t his section are approximate values in mass percent. _ SAE INTERNATIONAL J1562
20、 Reaffirmed APR2015 2 of 94.1.2 Zinc Coatings Coatings that are considered essentially pure zinc coatings are typically referred to as hot-dip galvanized or electrogalvanized. Hot-dip galvanized coatings may contain small amounts of aluminum, lead, and antimony which are added to enhance coating pro
21、perties. Electrogalvanized coatings are typically high-purity zinc and control only trace amounts of other elements. 4.1.3 Alloy Coatings The most common alloy coatings are zinc-iron alloys. They are used to enhance spot welding and certain aspects of paintability. Zinc-iron coatings can be produced
22、 by the electroplating process in which zinc and iron are codeposited onto the steel sheet surface. The iron content of the coating is controlled by adjustment of electrolytic solution and plating current. When processed on a hot-dip coating line, the zinc-iron coating is called Galvannealed and is
23、produced using a thermal process after hot dipping. This process promotes diffusion of iron from the steel base into the coating which typically contains an average of 8 to 12% iron. Aluminum-zinc-silicon and zinc-aluminum hot-dip alloyed coatings are produced by conventional hot-dip coating process
24、es. The molten coating bath contains approximately the same composition as the coating on the steel. Zinc-nickel (20% nickel) alloy electroplated coatings are produced by conventional electroplating techniques. The plating electrolyte contains zinc and nickel ions that are codeposited as an alloy mi
25、xture. 4.2 Coating Mass This document addresses the needs of automotive engineering by identifying the coating masses most commonly used in component design and by expressing the coating mass measurements as a minimum and maximum single-spot test for a given side. For example, 70 g/m2is the minimum
26、coating mass on a single-spot test for the designated side of coating Category 70. The maximum coating mass for this Category is 100 g/m2for hot-dip galvanized products, or 90 g/m2for electroplated products. This definition of coating mass represents a departure from the practice described in ASTM m
27、ethods A653/A653M for hot-dipped galvanized steel sheet, and ASTM method A879/A879M, except for Table 1, for electrolytic zinc-coated steel sheet. The ASTM Standard Specifications have been the principal public standards prior to the publication of this document. The thickness of the coating is not
28、an acceptable practice for specifying the quantity of coating to be deposited on the base steel. 4.3 Coating Designation This document uses a nine-character designation that identifies the coating process, coating mass, and coating composition of each side, and the intended use of the coated steel w
29、ith regard to the surface appearance quality required, i.e., exposed and unexposed. The terms “exposed” and “unexposed” are not related to corrosion requirements. The coating designation shall be stated using the following procedure: a. 1st and 2nd Characterrepresent the coating process where HD = h
30、ot dip galvanized, and EG = electrogalvanized b. 3rd and 4th CharacterThe numbers shown in the “Coating Mass Category” column of Table 1 indicates the coating mass of the unexposed side c. 5th CharacterCoating composition of the unexposed side where G = zinc coating, A = zinc-iron coating, N = zinc-
31、nickel coating, X = other than G, A, or N d. 6th and 7th CharacterThe numbers shown in the “Coating Mass Category” column of Table 1 indicates the coating mass of the other side (exposed side, if applicable) _ SAE INTERNATIONAL J1562 Reaffirmed APR2015 3 of 9e. 8th CharacterCoating composition of th
32、e other side (exposed side, if applicable) where G = zinc coating, A = zinc-iron coating, X = other than G, A, or N f. 9th CharacterIntended use where E = exposed, U = unexposed, and Z = semi-exposed TABLE 1 - RECOMMENDED COATING MASS FOR GALVANIZED STEEL SHEET Coating Mass Category Coating Mass Per
33、 SideSingle Spot Test Hot Dipped and Electroplated min g/m2Coating Mass Per Side Single Spot Test Hot Dipped max g/m2Coating mass Per SideSingle Spot Test Electroplated max g/m200 00 NA 00 20 20 50 30 30 30 60 45 40 40 70 55 45 45 75 60 50 50 80 70 55 55 85 75 60 60 90 80 70 70 100 90 90 90 120 110
34、98 98 130 130 NOTE: For approximate conversion from mass to thickness, use: microns = g/m2x 0.14 mils = g/m2x 0.006 Examples of the more commonly used galvanized steels expressed in terms of Table 1 are: EG70G70GE = 70 g/m2minimum of zinc coating on each side for an exposed application. HD70G20AE =
35、70 g/m2minimum of zinc coating on the unexposed side and 20 g/m2minimum of zinc-iron coating on the exposed side for an exposed application. HD90G90GU = 90 g/m2minimum of zinc coating on each side for an unexposed application. HD45A45AU = 45 g/m2minimum of zinc-iron coating on each side for an unexp
36、osed application. EG30N30NE = 30 g/m2minimum of zinc-nickel coating on each side for an exposed application. EG70G00XE = 70 g/m2minimum of zinc coating on the unexposed side and no coating on the exposed side (“one-side”) for an exposed application. 4.4 Coating Mass Determination The coating mass re
37、quirements in Table 1 refer to any single spot test per side. There are several methods of determining coating mass. Modern galvanizing lines use X-ray fluorescence techniques described in ASTM method A754/A754M to continuously monitor coating mass throughout the coil during the galvanizing process.
38、 The referee method is the “weigh-strip-weigh” method as described in ASTM method A90/A90M except, coating on each side must be measured separately. 4.4.1 Minimum Coating Mass If the initial testing produces a value less than the minimum shown in Table 1, two additional test specimens shall be taken
39、 from the same lift of blanks or cut lengths or coil, except that no portion of the retest specimen may be any closer than 25 mm to the edge of the as-received steel. Both retests must conform to the minimum value of Table 1 for the Coating Mass Category specified; otherwise, the lift of blanks or c
40、ut lengths or coil can be considered unacceptable. _ SAE INTERNATIONAL J1562 Reaffirmed APR2015 4 of 94.4.2 Maximum Coating Mass If the initial testing produces a value more than the maximum shown in Table 1, three additional test specimens shall be taken from the same lift of blanks or cut lengths
41、or coil, except that no portion of the retest specimen may be any closer than 25 mm to the edge of the as-received steel. The average of the three retest specimens must conform to the maximum value of Table 1 for the Coating Mass Category specified, and no retest specimen may exceed the maximum in T
42、able 1 by more than 30%. Otherwise, the lift of blanks or cut lengths or coil can be considered unacceptable. 4.5 Coated Surface Finish and Conditions The user of galvanized steel should specify either exposed (E), semi-exposed (Z), or unexposed (U), surface quality as required (see 4.3). The steel
43、suppliers responsibility is to supply a galvanized surface finish suitable for the application. The following coated surfaces and conditions are available. References to spangle conditions do not apply to zinc-iron or electrodeposited coatings since these coatings do not develop spangles. Unexposed
44、(U) hot-dip applications should be supplied with a minimized spangle surface finish. 4.5.1 Regular Spangle (Hot-Dipped Only) A commonly seen type of coating in non-automotive markets is regular spangle, typified by the flower-like or snowflake-like design (spangle pattern) that results from an uneve
45、n topographical relief, which shows prominently through most primer/paint systems used in the automotive industry. Regular spangle coatings are not considered acceptable for automotive applications. 4.5.2 Minimized Spangle (Hot-Dipped Only) By application of various processing techniques during the
46、transition period when the zinc coating freezes, the size and texture of the developing spangle can be altered (refined) substantially. The intent of these processing techniques is to produce very small spangles, and thereby, decrease the surface roughness associated with relief of the spangles norm
47、ally formed. The surface finish of minimized spangle may be suitable for some less visible exposed applications. When the spangle is minimized to the extent that it is not visible to the unaided eye, the finish is termed spangle-free. Product intended for “U,” Unexposed applications. 4.5.3 Extra Smo
48、oth (Hot-Dipped Only) Following the galvanizing operation, rolling processes can be used to improve the smoothness of the zinc-coated steel. The most frequently used rolling process is called temper rolling (skin passing). This additional processing step is used to produce a very uniform matte surface that is readily painted. Usually, the extra smooth product is produced by temper rolling minimized spangle product. Product intended for “Z,” Semi-ex
