1、SAE Technical Standards 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 entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.QUESTIONS REGARDING THIS DOCUMENT: (724) 772-8512 FAX: (724) 776-0243TO PLACE A DOCUMENT
3、 ORDER; (724) 776-4970 FAX: (724) 776-0790SAE WEB ADDRESS http:/www.sae.orgCopyright 1991 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001STANDARDAn American National StandardJ1837ISSUEDJUN91Issued 1991-06-14EL
4、ECTROPLATE REQUIREMENTS FOR DECORATIVE CHROMIUM DEPOSITS ON ZINC BASE MATERIALS USED FOR EXTERIOR ORNAMENTATIONForewordThis Document has not changed other than to put it into the new SAE Technical standards boardFormat.1. ScopeThis SAE Standard covers the physical and performance requirements for el
5、ectrodeposited copper,nickel, and chromium deposits on exterior ornamentation fabricated from die cast zinc alloys (SAE J468 alloys903 and 925), and wrought zinc strip (ASTM B 69). This type of coating is designed to provide a high degreeof corrosion resistance for automotive, truck, marine, and far
6、m usage where a bright, decorative finish isdesired.1.1 PurposeThis document details the physical and chemical properties that are necessary to optimize coatingappearance and durability of decoratively plated parts. When properly applied, the electroplate described inthis document has a bright, high
7、ly reflective, and specular finish with an inherently high degree of corrosionresistance. The coatings resistance to a corrosive environment is highly dependent on the propermaintenance of the processes used to produce the coating. Since the treatment of processing variables isoutside the scope of t
8、his document, it is important for applicators of this coating to develop an intimateknowledge of their process, and control all parameters that affect the quality of the end product. The use oftechniques such as statistical process control (SPC), capability studies, design of experiments, processopt
9、imization, etc., are critical to produce a material of consistently high quality.The subjects included in this document are: substrate preparation, metal finishing, plate thickness,electrochemical potential difference, ductility, chromium microdiscontinuity, accelerated corrosion, adhesion,bend test
10、ing, and sampling. The appropriate specification limits and test methods are described in eachsection. Where possible, the test methods specified are well established and accepted within the platingindustry. In a few instances, several test methods are specified. In these cases, it is up to the purc
11、haser andsupplier to agree on the test method to be used.2. References2.1 Applicable PublicationsThe following publications form a part of this specification to the extent specifiedherein. The latest issue of SAE publications shall apply.2.1.1 SAE PUBLICATIONAvailable from SAE, 400 Commonwealth Driv
12、e, Warrendale, PA 15096-0001.SAE J468Zinc Alloy Ingot and Die Casting CompositionsCOPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling ServicesSAE J1837 Issued JUN91-2-2.1.2 ASTM PUBLICATIONSAvailable from ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959.ASTM
13、B 69Specification for Rolled ZincASTM B 252Preparation of Zinc Alloy Die Castings for Electroplating and Conversion CoatingsASTM B 368Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing (CASS Test)ASTM B 374Standard Definitions of Terms Relating to ElectroplatingASTMB456Electrodeposited Coatings
14、 of Copper Plus Nickel Plus Chromium and Nickel PlusChromiumASTM B 487Measurement of Metal and Oxide Coating Thickness by Microscopical Examination of aCross SectionASTM B 490Micrometer Bend Test for Ductility of ElectrodepositsASTM B 504Measurement of Thickness of Metallic Coatings by the Coulometr
15、ic MethodASTM B 507Design of Articles to be Electroplated on RacksASTM B 537Rating of Electroplated Panels Subjected to Atmospheric ExposureASTM B 556Measurement of Thin Chromium Coatings by the Spot TestASTM B 571Adhesion of Metallic CoatingsASTM B 602Attribute Sampling of Electrodeposited Metallic
16、 Coatings and Related FinishesASTMB697Selection of Sampling Plans for Inspection of Electrodeposited Metallic Coatings andRelated Finishes on ProductsASTM B 762Variables Sampling of Metallic and Inorganic CoatingsASTMB764Simultaneous Thickness and Electrochemical Potential Determination of Individua
17、l Layersin Multilayer Nickel Deposit (STEP Test)3. Definitions3.1 Significant SurfacesThese are defined as surfaces that are visible when the finished component isassembled onto the vehicle and is observed in normal viewing position. Nonsignificant surfaces that maycause corrosion products to run on
18、to significant surfaces are significant. Also, nonvisible surfaces, whendesignated by the customer, are significant.3.2 MicrodiscontinuousA chromium deposit in which microscopic voids exist in the chromium, exposing theunderlying nickel layer. The production of suitable microscopic voids or sites in
19、 the chromium layer causes adispersion of the corrosion potential over a relatively large surface area. The resulting corrosion potentialdispersion reduces the effects of localized high corrosion potentials and the associated large corrosion pits.3.2.1 ASTM B 374 provides definitions of the more com
20、mon terms related to plating.4. AppearanceAll parts manufactured to this document shall meet the visual requirements for color, luster, andother specific finish standards agreed on between the customer and supplier, on all significant surfaces.Standard panels or typical production parts should be us
21、ed to define the various appearance levels for majorsurfaces and parting line finishes.Various classes or types of finish may be specified by the purchaser. The production drawing should indicate,via symbols or notes, the specifics of these requirements. Visual standards, including textured surfaces
22、tandards, may be used to supplement the drawing notes showing minimum acceptable appearanceconditions.5. Substrate PreparationThe substrate surface finish can affect the plated appearance. Suitable precautionsin casting, forming, finishing, and cleaning must be taken to assure a satisfactorily finis
23、hed plated part.Evidence of surface porosity, stress cracks, blisters, or other surface defects may indicate improper substratepreparation or inferior castings that may not have adequate durability after plating. The proper practices forpreparing the zinc die casting for plating are discussed in AST
24、M B 252.COPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling ServicesSAE J1837 Issued JUN91-3-6. Design GuidelinesAn entire document could be written on “design guidelines“ and the reader is urged toconsult a document such as ASTM B 507.7. Metal FinishingBuffing or other m
25、echanical treatments of the substrate, copper or nickel deposits arepermitted provided that minimum plating thickness, chromium microdiscontinuity, and other applicablerequirements are met following these treatments. Buffing of the final chromium plate is not permitted as it willadversely affect cor
26、rosion resistance.8. Plate Thickness8.1 The plate thicknesses listed in Table 1 shall be met on all areas of the significant surfaces. These thicknessesalso apply to nonsignificant surfaces which, on corroding, may drip onto or otherwise affect a significantsurface.a. Generally consists of a cyanide
27、 copper layer. It is up to the customer and supplier to agree on whattype of copper or other plating process is utilized as the initial layer on zinc base parts.b. The copper layer may be plated from either a cyanide copper bath or an acid copper bath and it is upto the customer and supplier to agre
28、e on an acceptable plating bath.c. The use of a “high potential“ nickel layer (generally 2.5 m or 0.0001 in thick) between the bright andsemibright nickels can improve corrosion performance of the composite plate. The semibright nickelthickness may, therefore, be reduced by the thickness of the “hig
29、h potential“ nickel layer if approved bythe customer.d. If trivalent chromium is employed, the minimum thickness shall be 0.50 m (0.00002 in).8.2 If, due to part geometry, the specified plating thickness on significant surfaces cannot be met, the customerand supplier shall agree on a minimum plate t
30、hickness or the use of an alternate coating method, e.g., auxiliaryanodes.8.3 Thickness MeasurementsThe thickness of the individual copper and nickel layers may be determinedusing the microscopic method, ASTM B 487, or the coulometric method, ASTM B 504. The nickel layers mayalso be measured using t
31、he “STEP“ test, ASTM B 764. Chromium thickness may be measured using ASTM B504 or the spot test, ASTM B 556. In case of disputes, the microscopic method for measuring thickness shallbe the referee method.TABLE 1PLATE THICKNESSThickness, m (minimum) in (minimum)Copper Strike 5 (a) 0.0002Copper 15 (b)
32、 0.0006Semibright Nickel 20 0.0008Bright Nickel 10 (c) 0.0004Total Semibright and Bright Nickel 30 0.0012Microdiscontinuous Chromium 0.25 (d) 0.00001COPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling ServicesSAE J1837 Issued JUN91-4-9. “Step“ Test Requirements9.1 Procedu
33、reThe “STEP“ test shall be carried out in accordance with ASTM B 764. To obtain reliable andreproducible results, the following precautions should be adhered to:a. Prevent the reference electrode from drying out when not in use by keeping it immersed in either water,“STEP“ test electrolyte or dilute
34、 (5 to 10%) hydrochloric acid solution.b. Run sufficient verification tests on a primary or secondary standard to insure that the instrument isworking properly, before carrying out a test on an unknown sample. If the STEP value of the primarystandard or secondary standard cannot be reproduced to wit
35、hin at least 5% of the reported value ofthe standard after three attempts, the instrument should be thoroughly checked for possible problems,e.g., plate buildup on inside of cell, faulty reference electrode, miscalibrated chart recorder, etc.Primary standard test panels are available from the Nation
36、al Institute of Standards and Technology,1while some instrument suppliers provide secondary standards. Tertiary standards may be actual partsor prepared plated panels that have been calibrated against a primary or secondary standard.c. Keep plate buildup on the inside surfaces of the metal test cell
37、 to a minimum by frequent cleaning.d. Make sure the pH of the test electrolyte is 3.0 0.1 when preparing new solution or checking oldsolution.9.2 Interpretation of Resultsa. The “STEP“ test may be used to measure the thickness of individual nickel layers when the instrumentis properly calibrated. Th
38、e thickness of the individual nickel layers shall meet the requirements of thisdocument (See 8.1).b. Measurements should normally be made in low to medium current density areas on significantsurfaces whenever part geometry permits. The customer specified plating thickness check points areusually sui
39、table locations for making “STEP“ test measurements. High current density areas of a partcan be expected to exhibit values at least 15 to 20 mV greater than the low current density areas of thesame part.c. At least two measurements should be made at any given test site and the average value reported
40、.Test spots must not touch or overlap each other. The individual readings at any one site should notvary from each other by more than 10%. Large variations suggest poor technique, faulty equipment, ordefective deposits (e.g., cracks, pits, dirt inclusion, etc.).d. The millivolt “STEP“ potential diff
41、erence between the various nickel layers shall be measured at themid or low current density areas (See 9.2 b) and shall exhibit the relative values and activities listedas follows:1. 100 mV: Minimum difference between bright and semibright nickel layers with the bright nickel moreactive than the sem
42、ibright. A difference of at least 125 mV is recommended as the statistical meanwith values of 100 mV as the absolute minimum. Maximum values have yet to be determined, butgenerally should not exceed 200 mV.2. 20 mV: Minimum difference between the bright nickel and the high activity nickel strike (be
43、tween thesemibright and bright nickel) when one is present. The high activity nickel strike shall be more activethan the bright nickel layer.3. 20 mV: Maximum difference between the bright nickel and any subsequent nickel strike ormicrodiscontinuous nickel layer when one is present. This layer shall
44、 be less active than, or equal to,the activity of the bright nickel layer.1. National Institute of Standards and Technology Office of Standard Reference Materials, Room B-311 Chemistry Building, Gaithersburg, MD 20899.COPYRIGHT Society of Automotive Engineers, Inc.Licensed by Information Handling Se
45、rvicesSAE J1837 Issued JUN91-5-e. It is stressed that successfully meeting the “STEP“ requirements of this document without conformingto other deposit requirements, such as thickness, ductility, chromium microdiscontinuity, CASS test,etc., may result in premature failure of the plated part in servic
46、e. All the requirements of this documentmust be complied with to achieve maximum corrosion protection.10. DuctilityTest Method: ASTM B 490The ductility of the composite electrodeposit on the finished part is considered acceptable when foils plated outof the individual nickel baths meet or exceed the
47、 following values:Semibright Nickel 67%Bright Nickel 11%NOTEA fully ductile individual nickel layer will have a foil test value 100% when computed using theformula D = 100 T/(2R-T).11. Specifications for Microdiscontinuity11.1 Determination of Microdiscontinuity and Active SitesDetermination of micr
48、odiscontinuity after chromiumplate, and active sites after corrosion testing, shall be conducted as per ASTM B 456, Appendix X4. However,to determine active sites, the chromium layer in the area to be examined shall be stripped using hydrochloricacid (concentrated), so that the corrosion sites in th
49、e nickel layer are more easily seen and counted.11.2 Microdiscontinuity After Chromium PlateThere shall be a minimum of 10 000 pores/cm2 (64 000/in2).A maximum quantity of pores has not been established, but is dictated by visual acceptance, both before andafter environmental testing, as agreed on between the customer and supplier. (The minimum number of cracksrequired when a trivalent chromium deposit is used, has not been established.)11.3 Active Sites After Corrosion Testing (CASS)There shall be a minim
