1、Designation: B 537 70 (Reapproved 2007)Standard Practice forRating of Electroplated Panels Subjected toAtmospheric Exposure1This standard is issued under the fixed designation B 537; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 hav
3、e beenexposed 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
4、to acceleratedtests such as those covered by Practice B117, Method B 287,Test Method B 368, and Test Method B 380.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
5、 cathodic 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) Apparat
6、usB 287 Method of Acetic Acid-Salt Spray (Fog) Testing3B 368 Test Method for Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing (CASS Test)B 380 Test Method of Corrosion Testing of DecorativeElectrodeposited Coatings by the Corrodkote Procedure2.2 ASTM Adjunct:4Dot charts (9 charts, 812 by 11 i
7、n.) (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 from cor
8、rosion 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. Accordingly, this
9、 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” number or
10、 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 (see Note
11、 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 may be done
12、 by the use of1This practice is under the jurisdiction of ASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.08.03on Decorative Coatings.Current edition approved Oct. 1, 2007. Published October 2007 . Originallyapproved in 1970. Last previous ed
13、ition approved in 2002 as B 537 70 (2002)e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.4Color
14、 reproductions of these photographs are available from ASTM Interna-tional Headquarters. Order Adjunct No. ADJB0537. Original adjunct produced in1987.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.agreed symbols for the most common
15、defects (Appendix X1)and abbreviations for degree or severity of these defects.4. Types of Defects4.1 “Protection” defects include crater rusting (Note 2),pinhole rusting, rust stain, blisters (Note 3), and any otherdefects that involve basis metal corrosion.NOTE 2“Rusting” or “rust” as used in this
16、 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 3Blisters on plated zinc die casting usually connote basis metalcorrosion; but the inspectors judgment
17、 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 that detract fromthe appearance (that is, the commercial acceptability) of thepanel. Typical are:
18、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 panels showing major amounts of such defects.Peeling of the coating from the substrate, or of one
19、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 exposure. In that case, aninspection should be made and recorded before the panels are exposed.5.1 Pa
20、nels 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 clouds should be avoided, andvarious angles of inspection should be tried to ensure thatdefects show
21、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 mild soap solution followed by water rinse; butno pressure should be exerted in this procedure such a
22、s 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 include only those that can be seen with the unaided eye(Note 5) at normal reading distance.NOTE 5“U
23、naided 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 Edge defects, occurring within 6.5 mm (14 in.) of theedges of a panel, may be noted in the description
24、 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 thepanel may be desirable to study one or another aspect of itscondition. Such procedure shall be confi
25、ned 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 areacovered by protection defects, by the following equation:R 5 3 2 2 log A! (1)where R = rating and A
26、= 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 wouldlead to ratings greater than 10 for panels with extremely smalldefective areas. Rating 10, accordingl
27、y, 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 but not perfect.Fractional ratings below 9, although normally not especiallyuseful, may be assigne
28、d 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 and charts4are 10 by 15 cm (4 by 6 in.) tofacilitate comparison with the panel being inspected. Thes
29、tandards 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 rate 0.6.2.1 The types of corrosion defects normally encountereddiffer according to the type of atmo
30、spheric 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 the latteratmosphere also tends to be more severe with regard todegradation of the coating system bu
31、t 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 helpful inassessing panels exposed to marine atmospheres, whereas dotcharts can be used for industri
32、al 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 nearly aspossible with one of the standards. If the panel is somewhatbetter than standard ( X) but n
33、ot as good as standard (X +1)itTABLE 1 Protection Rating Versus Area of DefectArea of Defect (in percent) Rating010To 0.1 90.1to0.25 80.25 to 0.5 70.5to1.0 61.0to2.5 52.5to5 45to10 310 to 25 225 to 50 150 0B 537 70 (2007)2is rated (X); if somewhat worse than standard (X) but not as badas standard (
34、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 individu-ally as in 6.3; but when the entire group has been rated, theratings should be reviewed to
35、 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 changedduring the course of the inspection, owing to fatigue, change inlighting conditions, has
36、te 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 all of the panels inorder to merit.7. Assignment of Appearance Rating7.1 This recommended pract
37、ice 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. Therefore,the appearance rating cannot be assigned with the same degreeof precision as can the pr
38、otection 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 exhibit new types and modes of deterioration.7.1.2 Unlike the protection rating, the appearance
39、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.7.2 The appearance rating is based, in the first instance, onthe protection rating. Since corr
40、osion 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 affecting only the coating, the appearancerating is the same as the protection rating. If there ar
41、e 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 follows as the “penalty.”7.3 The inspector must decide, on the basis of best currentpractice and
42、 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 inevitably enter into thedecision.7.3.1 Defects only slightly damaging may include very lightsu
43、rface 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 patterns typical of some kinds of chromium plate,and so forth. Such defects, to be categorized as
44、“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 can be classified as very slight, two ifslight.NOTE 6If fractional rating was used for the pro
45、tection 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 appearance rating may not be higherthan the protection rating.7.3.2 Defects moderately damaging inc
46、lude 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 or stain that, although removable, requires more drastictreatment than routine washing.7.3.2.1
47、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 severe.7.3.3.1 A penalty of 5 or more points, up to the maximumavailable, is assessed for severe s
48、urface 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 described in the foregoing should be satis-factory for assessing relatively good panels. Difficulties
49、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 rating has no meaning. Suchpanels may arbitrarily be assigned one of two appearanceratings: (1) if th
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