1、Designation: B537 70 (Reapproved 2013)Standard Practice forRating of Electroplated Panels Subjected toAtmospheric Exposure1This standard is issued under the fixed designation B537; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers a preferred method for evaluatingthe condition of electroplated test panels that have b
3、eenexposed to corrosive environments for test purposes. It is basedon experience in use of the method with standard 10- by 15-cm(4- by 6-in.) panels exposed on standard ASTM racks atoutdoor test sites in natural atmospheres. It has been used alsofor rating similar panels that have been subjected to
4、acceleratedtests such as those covered by Practice B117, Method B287,Test Method B368, and Test Method B380. Any modificationsneeded to adapt the method to rating actual production parts arenot considered in this practice.1.2 This practice refers only to decorative-protective coat-ings that are cath
5、odic to the substrate, typified by nickel/chromium or copper/nickel/chromium on steel or zinc diecastings. It is not intended for use with anodic sacrificialcoatings such as zinc and cadmium on steel.2. Referenced Documents2.1 ASTM Standards:2B117 Practice for Operating Salt Spray (Fog) ApparatusB28
6、7 Method of Acetic Acid-Salt Spray (Fog) Testing(Withdrawn 1987)3B368 Test Method for Copper-Accelerated Acetic Acid-SaltSpray (Fog) Testing (CASS Test)B380 Test Method for Corrosion Testing of DecorativeElectrodeposited Coatings by the Corrodkote Procedure2.2 ASTM Adjunct:4Dot charts (9 charts, 812
7、 by 11 in.) (9 color photos, 3 by 5in.)3. Basis of Procedure3.1 The rating method described in this recommendedpractice is based on the recognition that typical decorative-protective deposits such as nickel/chromium, with or without acopper undercoat, have two functions: ( 1) to protect thesubstrate
8、 from corrosion and thus prevent degradation ofappearance caused by basis metal corrosion products (forexample, rust and rust stain); and (2) to itself maintain asatisfactory appearance.Although these functions overlap, theycan be evaluated separately and it is frequently desirable to doso. Accordin
9、gly, this practice assigns separate ratings to (1)appearance as affected by corrosion of the substrate and (2)appearance as affected by deterioration of the coating itself.3.2 The rating number assigned to the ability of the coatingto protect the substrate from corrosion is called the “protec-tion”
10、number or rating.3.3 The rating number assigned to the inspectors judgmentof the overall appearance of the panel, including all defectscaused by the exposure (Note 1), is called the “appearance”number or rating.NOTE 1Panels that are not “perfect” even before being exposedshould normally be rejected
11、(see Note 4).3.4 The result of inspecting a panel is recorded as twonumbers separated by a slash (/), the protection number beinggiven first.3.5 In addition to recording the numerical rating of a panel,the inspector should note the type(s) and severity of defect(s)contributing to the rating. This ma
12、y be done by the use ofagreed symbols for the most common defects (Appendix X1)and abbreviations for degree or severity of these defects.1This practice is under the jurisdiction of ASTM Committee B08 on Metallicand Inorganic Coatingsand is the direct responsibility of Subcommittee B08.05 onDecorativ
13、e Coatings.Current edition approved Dec. 1, 2013. Published December 2013. Originallyapproved in 1970. Last previous edition approved in 2007 as B537 70 (2007).DOI: 10.1520/B0537-70R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceast
14、m.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4Color reproductions of these photographs are available from ASTM Interna-tional Headquarter
15、s. Order Adjunct No. ADJB0537. Original adjunct produced in1987.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Types of Defects4.1 “Protection” defects include crater rusting (Note 2),pinhole rusting, rust stain, blisters (Note 3)
16、, and any otherdefects that involve basis metal corrosion.NOTE 2“Rusting” or “rust” as used in this document includescorrosion products of the substrate and is not confined to iron or steel: thewhite corrosion products of zinc die castings and aluminum, for example,are included in this term.NOTE 3Bl
17、isters on plated zinc die casting usually connote basis metalcorrosion; but the inspectors judgment may be required to decide whethera blister does or does not arise at the substrate-coating interface.4.2 “Appearance” defects include, the addition to thosecaused by basis metal corrosion, all defects
18、 that detract fromthe appearance (that is, the commercial acceptability) of thepanel. Typical are: surface pits, “crows feet,” crack patterns,surface stain, and tarnish.4.3 Defects developing on exposure that reflect improperpreparation or plating should be noted but no attempt should bemade to rate
19、 panels showing major amounts of such defects.Peeling of the coating from the substrate, or of one coat fromanother, is the principal such defect.5. Preparation for and Manner of InspectionNOTE 4It may be desirable to expose panels for test even though theyare defective in certain respects before ex
20、posure. In that case, aninspection should be made and recorded before the panels are exposed.5.1 Panels may be inspected on the exposure racks or maybe removed to a more suitable location if necessary. Lightingduring inspection should be as nearly uniform as possible;direct reflection from sun or cl
21、ouds should be avoided, andvarious angles of inspection should be tried to ensure thatdefects show up.5.2 If the condition of the panels allows, inspection shouldbe made in the “as-is” condition. If dirt, salt deposits, and soforth, make it impractical to inspect them, panels may besponged with a mi
22、ld soap solution followed by water rinse; butno pressure should be exerted in this procedure such as wouldtend to upgrade the rating by, for example, cleaning off rust orrust stain. Panels should be allowed to dry before inspectingthem.5.3 Defects to be noted and taken into account in ratingpanels i
23、nclude only those that can be seen with the unaided eye(Note 5) at normal reading distance.NOTE 5“Unaided eye” includes wearing of correctional glasses if theinspector normally wears them.5.3.1 Optical aids may be used to identify or study defectsonce they are found by unaided eye inspection.5.4 Edg
24、e defects, occurring within 6.5 mm (14 in.) of theedges of a panel, may be noted in the description but are notcounted in arriving at the numerical rating. Similarly contactand rack marks, mounting holes, and so forth, should bedisregarded.5.5 Rubbing, polishing, and so forth, of the surface of thep
25、anel may be desirable to study one or another aspect of itscondition. Such procedure shall be confined to the minimumarea absolutely necessary for the purpose, preferably not morethan 1 cm2of a 10- by 15-cm panel.6. Assignment of Protection Rating6.1 The numerical rating system is based on the areac
26、overed by protection defects, by the following equation:R 5 3 2 2 logA! (1)where R = rating and A = percentage of the total area cov-ered by defects. R is rounded off to the nearest whole number,leading to the tabulation given in Table 1.6.1.1 Strict application of the equation given in 6.1 wouldlea
27、d to ratings greater than 10 for panels with extremely smalldefective areas. Rating 10, accordingly, is arbitrarily assignedto a panel with no defects, and the equation operates at ratings9 and below.6.1.2 If desired, fractional ratings between 9 and 10 may beassigned to panels judged better than 9
28、but not perfect.Fractional ratings below 9, although normally not especiallyuseful, may be assigned if desired.6.2 As an aid in judging the defective area, standards ofcomparison, consisting of photographs of panels or of dotcharts are made part of this practice. See Appendix X2. Thesephotographs an
29、d charts4are 10 by 15 cm (4 by 6 in.) tofacilitate comparison with the panel being inspected. Thestandards represent as nearly as possible the maximum amountof corrosion permissible for a given rating; there is a standardfor each rating 1 through 9.Apanel worse than the standard forrating 1 would ra
30、te 0.6.2.1 The types of corrosion defects normally encountereddiffer according to the type of atmospheric exposure. Typicaldecorative deposits exposed to marine atmospheres often tendto fail by crater rusting, whereas in industrial atmospheres, theyare more likely to exhibit pinpoint rusting; and th
31、e latteratmosphere also tends to be more severe with regard todegradation of the coating system but somewhat less severewith regard to basis metal corrosion. For this reason, the samestandard comparison photographs or charts are not suitable foruse at both types of locations; photographs are more he
32、lpful inassessing panels exposed to marine atmospheres, whereas dotcharts can be used for industrial locations (Appendix X2).6.3 In rating any given panel, it is recommended that theappropriate series of standards be placed beside it and the basismetal corrosion defects in the panel be matched as ne
33、arly aspossible with one of the standards. If the panel is somewhatbetter than standard (X) but not as good as standard (X +1)itis rated (X); if somewhat worse than standard (X) but not as badTABLE 1 Protection Rating Versus Area of DefectArea of Defect (in percent) Rating010To 0.1 90.1to0.25 80.25
34、to 0.5 70.5to1.0 61.0to2.5 52.5to5 45to10 310 to 25 225 to 50 150 0B537 70 (2013)2as standard (X 1) it is rated (X 1).At the inspectors option,decimal fractional ratings may be assigned.6.3.1 If a large group of panels is being inspected at onetime, it is recommended that the panels be assessed indi
35、vidu-ally as in 6.3; but when the entire group has been rated, theratings should be reviewed to make sure that ratings assignedactually reflect the relative merits of the panels. This acts as acheck on individual ratings and aids in ensuring that theinspectors judgment or frame of reference has not
36、changedduring the course of the inspection, owing to fatigue, change inlighting conditions, haste to finish the job, or other causes. Onemethod of facilitating this comparison is to remove individualpanels from their racks and place them beside other panels. Itmay be advisable to physically arrange
37、all of the panels inorder to merit.7. Assignment of Appearance Rating7.1 This recommended practice recognizes that whereas thedegree of protection afforded the substrate can be assessedfairly objectively in accordance with Section 6, the assessmentof appearance depends on many subjective factors. Th
38、erefore,the appearance rating cannot be assigned with the same degreeof precision as can the protection rating.7.1.1 There are many modes of deterioration in appearancementioned in 4.2 but this list is not exhaustive, and as newplating systems are developed and introduced to industry, theymay well e
39、xhibit new types and modes of deterioration.7.1.2 Unlike the protection rating, the appearance rating isbased not only on the area of the defects but also on theirseverity: the degree to which they would detract from thecommercial acceptability of an article of appearance similar tothat of the panel
40、.7.2 The appearance rating is based, in the first instance, onthe protection rating. Since corrosion of the substrate alsodetracts from appearance, the appearance rating can be nohigher than the protection rating.7.2.1 If basis metal corrosion is the only defect, there beingno additional defects aff
41、ecting only the coating, the appearancerating is the same as the protection rating. If there are surfacedefects not accounted for in the protection rating, the appear-ance rating will be one or more units lower than the protectionrating. This lowering of the appearance rating is referred to inwhat f
42、ollows as the “penalty.”7.3 The inspector must decide, on the basis of best currentpractice and opinion, whether a surface coating defect is (1)very slightly, (2) slightly (3) moderately, or (4) severelydamaging to the acceptability of the appearance. Guidelines aregiven below, but judgment factors
43、inevitably enter into thedecision.7.3.1 Defects only slightly damaging may include very lightsurface pitting that detracts little from the reflectivity, lighttarnish or stain easily removed by mild cleaning (such as wouldbe given, for instance, in normal car-washing practice), super-ficial crack pat
44、terns typical of some kinds of chromium plate,and so forth. Such defects, to be categorized as “slight,” mustnot render the finish commercially unacceptable.7.3.1.1 A penalty of 1 or 2 points (rating numbers) isassessed for appearance defects classified as slight. One pointis assessed if the defects
45、 can be classified as very slight, two ifslight.NOTE 6If fractional rating was used for the protection number, thiswould result in a fractional appearance rating; in that case the fractionalappearance rating may be retained, or rounded off to the nearest wholenumber, provided, however, that the appe
46、arance rating may not be higherthan the protection rating.7.3.2 Defects moderately damaging include the same typesas in 7.3.1 but more severe, so as to render the appearancequestionably acceptable from a commercial standpoint. Forexample, surface pits that begin to detract from reflectivity;tarnish
47、or stain that, although removable, requires more drastictreatment than routine washing.7.3.2.1 A penalty of 3 or 4 points (rating numbers) isassessed for appearance defects classified as moderate.7.3.3 Surface defects that render the panel definitely unac-ceptable in appearance are classified as sev
48、ere.7.3.3.1 A penalty of 5 or more points, up to the maximumavailable, is assessed for severe surface defects.7.4 The procedure for checking the ratings described in6.3.1 is of particular importance in assigning appearanceratings, and is strongly recommended.8. Low-Rated Panels8.1 The system describ
49、ed in the foregoing should be satis-factory for assessing relatively good panels. Difficulties may beencountered in attempting to rate severely corroded panels. Forexample, if a panel rates as low as 4 for protection, it may bedifficult to assess any additional appearance defects. At theoption of the inspector, this difficulty may be handled asfollows:8.1.1 Acutoff point may be chosen below which appearanceratings are deemed to be of no significance. For example, itmay be agreed that any panel with a protection rating of 5 is sounacceptable that an appearance ratin
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