1、Designation: D 4938 89 (Reapproved 2007)Standard Test Method forErosion Testing of Antifouling Paints Using High VelocityWater1This standard is issued under the fixed designation D 4938; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, 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 test method covers the determination of erosionrates for marine antifouling paint systems immers
3、ed in flowingnatural seawater.1.2 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 standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitation
4、s prior to use. For a specifichazard statement, see Section 7.2. Referenced Documents2.1 ASTM Standards:2A 569/A 569M Specification for Steel, Carbon (0.15 Maxi-mum Percent), Hot-Rolled Sheet and Strip Commericial3D 823 Practices for Producing Films of Uniform Thicknessof Paint, Varnish, and Related
5、 Products on Test PanelsD 1889 Test Method for Turbidity of Water3D 2200 Standard Pictorial Surface Preparation Standardsfor Painting 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
6、, Anticorrosion (Met-ric)3. Summary of Test Method3.1 Steel panels coated with the antifouling paint systemunder evaluation are positioned 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
7、one series oftest panels evaluated at the standard water velocity of 12 m/sand shall specify the length of time, temperature, salinity, andpH. Additional velocities may be conducted at the discretion ofthe customer.3.3 Color photographs and coating thickness measurementsshall be taken prior to expos
8、ure, at specified time intervals, andrepeated at the end of the test for comparison purposes.4. Significance and Use4.1 This test method is intended to measure the erosion ratesof ablative antifouling paint systems exposed to flowing waterat velocities designed to subject the paint system to shearst
9、resses experienced in service.4.2 Measurement of erosion rates are necessary to help inthe assessment of ablative antifouling paint film thicknessesrequired for fouling control between scheduled drydockings ofships, in the selection of materials, in producing qualityassurance, and in understanding t
10、he performance mechanism.4.3 The test data is intended to serve as a guide forpredicting the service life of ablative antifouling paints in orderto calculate the necessary paint thickness to fit specifieddeployment cycles. Erosion rates of antifouling paints inservice will vary depending on such fac
11、tors as: berthinglocation, geographic area of operation, salinity, pH, and tem-perature of seawater. It should also be recognized that 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 no
12、t been deter-mined.5. Apparatus5.1 Water Channel:5.1.1 High velocity flowing 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
13、 of a four-walled channel,rectangular in cross section, through which natural seawaterflows at varying linear velocities to simulate ships speeds.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibili
14、ty ofSubcommittee D01.45 on Marine Coatings.Current edition approved June 1, 2007. Published August 2007. Originallyapproved in 1989. Last previous edition approved in 2002 as D 4938 - 89 (2002).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at
15、serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.4Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http:/www.dodssp.daps.mil.1
16、Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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
17、.1.3.3 Channel flow orifice plate.5.1.4 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 beachieved in each velo
18、city test section. The Reynolds number,R, is calculated as follows:R 5 D 3 V 3 P!/U (1)where:FIG. 1 High Velocity Flow ChannelFIG. 2 Simplified Schematic of Flow ChannelW, mm Velocity, m/s50 1860 1575 12100 9150 6300 3FIG. 3 Cross-Section View of Test Panel Mounted in FlowChannel (Low Velocity Secti
19、on)D 4938 89 (2007)2D = equivalent diameter = 4 3 (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
20、calculated as follows:4 3 A 3 B!/2A 1 2B!# (2)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
21、 8 withthe following equipment:5.2.1 Microtome 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.
22、2 Natural seawater shall be continuously supplied 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
23、.2.3 Incoming seawater temperature and the channelseawater 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 D 1889.5.3.4 As a minimum, the seawat
24、er chemistry in the channel,averaged over the 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 A 569/A 569M shall be used in the channel. The panels shall measure1
25、8.75 cm high, 15 cm long, and 1.25 cm thick. The 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 D 823are positioned vertically and parallel to the flowing water tosimulat
26、e sheer stresses experienced by paints on the shipsunderwater 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
27、 except for downtime for panelinspection and seawater 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 p
28、rimer from the same manufacturer in accordancewith 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 D 823.7. Hazards7.1 Antifouling paints co
29、ntain toxic materials that couldcause skin and eye 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
30、with local, state, and federal governmentregulations 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 be
31、ing evaluated to near-white metal, Grade 212 inaccordance with Pictorial Standard D 2200, 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, whichev
32、er applies.8.3 Apply an antifouling topcoat in accordance with Mili-tary Specification DOD-P-24647 or the manufacturers recom-mendations, whichever applies.8.4 Apply additional coats of antifouling paint in accor-dance with Military Specification DOD-P-24647 or the manu-facturers instructions, which
33、ever applies. The last coat shalldry for a minimum of 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
34、 coating 2 6 0.5 cm/diameter applied in the center of 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 thick
35、ness measurements before and aftertesting (see 5.2).8.7 Panels are to be photographed prior to starting the testfor comparison with photographs taken at the conclusion of thetest.8.8 A specimen of exposed antifouling paint is carefullyremoved for examination in a single flake which includes afragmen
36、t of the noneroding reference. This 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.D 4938 89 (2007)38.9 Specimens are prepared
37、 for examination by microtomesectioning or by abrasive 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 sh
38、own in Fig. 5.9. Calculation9.1 The material loss is expressed as the erosion rate of theablative antifouling paint.9.2 The erosion rate is calculated by dividing the microme-ters of surface erosion by the duration of the test expressed inmonths at a specified speed.9.2.1 ExampleA 20-m erosion in 3
39、months equals 6.7m/month.9.3 The speed of the water in 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 reporte
40、d as 6.7m/month at 17.5 knots, etc.10. Report10.1 The 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
41、 anyauxiliary test velocities,10.1.4 Daily measurements 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
42、 paints; erosion testing; high velocity water;seawaterASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent r
43、ights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either f
44、or revision of this standard or for additional standardsand 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 heari
45、ng you shouldmake your views known to the ASTM Committee 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 or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).FIG. 4 Illustration of Material Lost During TestingFIG. 5 Actual MicrophotographD 4938 89 (2007)4
