1、Designation: D4938 89 (Reapproved 2013)Standard Test Method forErosion Testing of Antifouling Paints Using High VelocityWater1This standard is issued under the fixed designation D4938; 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 () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of erosionrates for marine antifouling paint systems immersed
3、in flowingnatural seawater.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 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
4、 standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For a specifichazard statement, see Section 7.2. Referenced Documents2.1 ASTM Standards:2A569/A569M Specification for Steel, Carbon (0.15Maximum, Percent), Hot-Rol
5、led Sheet and Strip Commer-cial (Withdrawn 2000)3D823 Practices for Producing Films of Uniform Thicknessof Paint, Varnish, and Related Products on Test PanelsD1889 Test Method for Turbidity of Water (Withdrawn2007)3D2200 Practice for Use of Pictorial Surface PreparationStandards and Guides for Paint
6、ing Steel Surfaces2.2 U.S. Military Specifications:4MIL-P-24441 Paint, Epoxy-PolyamideDOD-P-24647 Paint, Antifouling, Ship Hull (Metric)DOD-P-24655 Paint, Underwater Hull, Anticorrosion (Met-ric)3. Summary of Test Method3.1 Steel panels coated with the antifouling paint systemunder evaluation are po
7、sitioned in a high velocity waterchannel, similar to the type shown in Figs. 1-3, parallel to thepath of the flowing water.3.2 Exposure conditions shall include at least one series oftest panels evaluated at the standard water velocity of 12 m/sand shall specify the length of time, temperature, sali
8、nity, andpH.Additional velocities may be conducted at the discretion ofthe customer.3.3 Color photographs and coating thickness measurementsshall be taken prior to exposure, at specified time intervals, andrepeated at the end of the test for comparison purposes.4. Significance and Use4.1 This test m
9、ethod is intended to measure the erosion ratesof ablative antifouling paint systems exposed to flowing waterat velocities designed to subject the paint system to shearstresses experienced in service.4.2 Measurement of erosion rates are necessary to help inthe assessment of ablative antifouling paint
10、 film thicknessesrequired for fouling control between scheduled drydockings ofships, in the selection of materials, in producing qualityassurance, and in understanding the performance mechanism.4.3 The test data is intended to serve as a guide forpredicting the service life of ablative antifouling p
11、aints in orderto calculate the necessary paint thickness to fit specifieddeployment cycles. Erosion rates of antifouling paints inservice will vary depending on such factors as: berthinglocation, geographic area of operation, salinity, pH, and tem-perature of seawater. It should also be recognized t
12、hat someareas of the ship are subject to different erosion rates.4.4 The degree of correlation between results obtained fromthis test method and shipboard service has not been deter-mined.5. Apparatus5.1 Water Channel:1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Rela
13、ted Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.45 on Marine Coatings.Current edition approved June 1, 2013. Published June 2013. Originallyapproved in 1989. Last previous edition approved in 2007 as D4938 89 (2007).DOI: 10.1520/D4938-89R13.2For referenc
14、ed 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.3The last approved version of this historical standard is referenced onwww
15、.astm.org.4Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http:/www.dodssp.daps.mil.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.1.1 High velocity fl
16、owing water in a contained channel,similar to the type shown in Figs. 1-3, is used to inducehydrodynamic shear stresses on painted panels to determineerosion rates of ablative antifouling paints.5.1.2 The basic apparatus consists of a four-walled channel,rectangular in cross section, through which n
17、atural seawaterflows at varying linear velocities to simulate ships speeds.5.1.3 All wetted materials supplying seawater to and withinthe channel shall be nonmetallic with the following exceptions:5.1.3.1 Channel circulating pump impellers.5.1.3.2 Thermowells.5.1.3.3 Channel flow orifice plate.5.1.4
18、 One section of the channel shall permit testing of thepanels at a standard test velocity of 12 m/s. All sections of thechannel shall provide flow with fully formed turbulent charac-teristics. A minimum Reynolds number of 1 000 000 shall beFIG. 1 High Velocity Flow ChannelFIG. 2 Simplified Schematic
19、 of Flow ChannelW, mm Velocity, m/s50 1860 1575 12100 9150 6300 3FIG. 3 Cross-Section View of Test Panel Mounted in Flow Chan-nel (Low Velocity Section)D4938 89 (2013)2achieved in each velocity test section. The Reynolds number,R, is calculated as follows:R 5 D 3 V 3 P!/U (1)where:D = equivalent dia
20、meter=4(area of flowing liquid/wetted perimeter), m,V = velocity, in m/s,P = density of medium, kg/m3, andU = viscosity, P/s.For a channel with a rectangular cross section and a testpanel placed in the middle of the channel, the equivalentdiameter would be calculated as follows:4 3 A 3 B!/2A12B!# (2
21、)where:A = width of channel from side wall to panel face, m, andB = height of channel, m.5.2 Erosion Rate DeterminationErosion rates of ablativeantifouling paints are determined by using noneroding refer-ence points and measured in accordance with Section 8 withthe following equipment:5.2.1 Microtom
22、e or encapsulating/polishing equipment.5.2.2 Microscope with photomicrographic capability.5.3 Seawater Requirements:5.3.1 Seawater will be circulated through the channel at aconstant rate permitting testing at different flow velocities asshown in 9.3.5.3.2 Natural seawater shall be continuously supp
23、lied to thechannel during operation to eliminate stagnation or concentra-tion effects. During operation of the channel the following datashall be obtained and recorded on a daily basis:5.3.2.1 Seawater circulating rate.5.3.2.2 Seawater salinity and pH.5.3.2.3 Incoming seawater temperature and the ch
24、annelseawater temperature.5.3.3 Provisions shall also be made for supplying filteredseawater to the channel. A suitable filter is one which canreduce turbidity to12 Jackson Turbidity Unit in accordancewith Test Method D1889.5.3.4 As a minimum, the seawater chemistry in the channel,averaged over the
25、course of the test run, shall be within thelimits specified below:Maximum MinimumSalinity, ppm 35 000 27 000pH 8.3 7.65.4 Test Panels:5.4.1 Steel test panels conforming to Specification A569/A569M shall be used in the channel. The panels shall measure18.75 cm high, 15 cm long, and 1.25 cm thick. The
26、 painted testpanels shall be subjected to a double sided exposure with bothsides exposed to similar hydrodynamic conditions.5.4.2 Test panels painted in accordance with Practice D823are positioned vertically and parallel to the flowing water tosimulate sheer stresses experienced by paints on the shi
27、psunderwater hull.5.4.3 The coating systems shall be applied in accordancewith the manufacturers instructions for both the anticorrosionand the antifouling paints.5.5 OperationThe channel shall be operated on a continu-ous basis during the test period except for downtime for panelinspection and seaw
28、ater filtering system backwashes. The totalrunning time of the test is defined as the total hours of actualchannel operation under fully flowing conditions.6. Application of Paints6.1 Antifouling paints under evaluation may be applied byspray over a primer from the same manufacturer in accordancewit
29、h the manufacturers directions or over 9 mils of epoxypolyamide paint conforming to Military Specification MIL-P-24441 with an appropriate tie-coat if necessary. Applicationshall be in accordance with Practice D823.7. Hazards7.1 Antifouling paints contain toxic materials that couldcause skin and eye
30、 irritation on contact and adverse physiologi-cal effects if ingested or inhaled. In the preparation of panelsand the application of various types of antifouling paints, theuse of appropriate protective clothing and equipment is re-quired consistent with local, state, and federal governmentregulatio
31、ns and recognized industrial and technical standards.Spills, overspray, and unused material shall not be flusheddown the drain but shall be disposed of as hazardous waste.8. Procedure8.1 Abrasive blast a minimum of three test panels for eachsystem being evaluated to near-white metal, Grade 212 inacc
32、ordance with Pictorial Standard D2200, to obtain a 1.0 to3.0 mils (25 to 75 m) surface profile.8.2 Apply an epoxy anticorrosion primer in accordance withMilitary Specifications DOD-P-24655 and MIL-P-24441, orthe manufacturers recommendations, whichever applies.8.3 Apply an antifouling topcoat in acc
33、ordance with Mili-tary Specification DOD-P-24647 or the manufacturersrecommendations, whichever applies.8.4 Apply additional coats of antifouling paint in accor-dance with Military Specification DOD-P-24647 or the manu-facturers instructions, whichever applies. The last coat shalldry for a minimum o
34、f 7 days before any erosion testing.8.5 Both sides of the painted test surfaces are provided withnoneroding reference (NER) points before immersion in thetest environment. The NER is an insoluble, tightly adherentvinyl or other suitable, compatible coating 2 6 0.5 cm/diameter applied in the center o
35、f the panel which will blanketa portion of the eroding surface. The NER preserves theoriginal outer surface of the antifouling and thus offers areference for comparison with the eroded surface during latermicroscopic examination.8.6 Take film thickness measurements before and aftertesting (see 5.2).
36、8.7 Panels are to be photographed prior to starting the testfor comparison with photographs taken at the conclusion of thetest.D4938 89 (2013)38.8 A specimen of exposed antifouling paint is carefullyremoved for examination in a single flake which includes afragment of the noneroding reference. This
37、specimen ismounted for microscopic analysis in a suitable medium such asparaffin wax or epoxy resin. Care is required to ensure that thespecimen is not damaged by solvent attack or heat evolutionduring this encapsulation.8.9 Specimens are prepared for examination by microtomesectioning or by abrasiv
38、e polishing to a plane surface.8.10 Subsequent microscopic examination yields the typicalimage shown in Fig. 4 and Fig. 5. The material lost during theduration of the test is clearly shown as measurement d in Fig.4. An actual photomicrograph is shown in Fig. 5.9. Calculation9.1 The material loss is
39、expressed as the erosion rate of theablative antifouling paint.9.2 The erosion rate is calculated by dividing the microm-eters of surface erosion by the duration of the test expressed inmonths at a specified speed.9.2.1 ExampleA 20-m erosion in 3 months equals 6.7m/month.9.3 The speed of the water i
40、n the channel expressed inmetres per second is correlated to a ships speed expressed inknots in accordance with the following table:Speed in Channel, m/s Speed, knots35.861179 17.512 23.315 29.118 35.09.3.1 ExampleA typical erosion rate is reported as 6.7m/month at 17.5 knots, etc.10. Report10.1 The
41、 final test report shall include the following data:10.1.1 List of the paints tested,10.1.2 Test durationdate started and date ended,10.1.3 Thickness readings before and after exposure. Reporttotal paint film loss at the standard test velocity and anyauxiliary test velocities,10.1.4 Daily measuremen
42、ts of the seawater temperature,salinity, and the pH,10.1.5 Speed of test water correlated to knots,10.1.6 Observation of the overall condition of painted panel,and10.1.7 Initial and final photographs of the test panels.11. Keywords11.1 antifouling paints; erosion testing; high velocity water;seawate
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45、rdsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Commit
46、tee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress
47、 or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).FIG. 4 Illustration of Material Lost During TestingFIG. 5 Actual MicrophotographD4938 89 (2013)4
