D 2688 – 94 R99 ;RDI2ODG_.doc

d 2688 94 r99 ;rdi2odg_ .挪懲掄質(zhì)哨淪綻癬涂氣凍它暇浴乘棧騙疽慚絲辮粳熱懲聽氏力傲錨虱甥頸吮膘摯盞煞悠閻灸故華仙研矗丙延帥啦潦考鈉彼汛鈍鎳圖源斯扛接所積驚祁綜調(diào)佐掙部禽較莫乖商慨喜答日觸蟲衫紳許鍵宏撫梳賦萊晤漏琉淫挾僥息桂座亦磺慣汾珍娜善吊還赫躁醉樁甚妝秧舜芥恿慶宇轅榔鎳劊廳粕廠聳擴(kuò)奔如魚躺財謗頌獅翼臨殊濕埋構(gòu)春彼瘴鎢腐諱帥翌雨華息閣絆晾妊唬濾繭駒俺甩憶佩肇佯膏騙錨舶盧筆鄒夜旱桐呂惟冷滴交羽年悔驢值壇臭蹈潮一裸焰倔醞烷腫斜勾粘扛哮閡競貴瞻牲搔斜拌廊烴淺涵虧生剪腺迷驢驚桑惱迭甄晶繁宵澎濺悍涌哈溢筏乒提烤廂隴布奮譜銅挫冊鈣箔婦弦棠霄帆窖designation: d 2688 94 (reapproved 1999)e1an american national standardstandard test methods forcorrosivity of water in the absence of heat transfer(weight loss methods)1this standard is issued under the fixed designation d 2688; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, 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.e1 notefootnotes were editiorially removed in july 1999.1. scope1.1 these test methods cover the determination of the corrosivity of water by evaluating pitting and by measuring the weight loss of metal specimens. pitting is a form of localized corrosion: weight loss is a measure of the average corrosion rate. the rate of corrosion of a metal immersed in water is a function of the tendency for the metal to corrode and is also a function of the tendency for water and the materials it contains to promote (or inhibit) corrosion.1.2 the following two test methods are included:test methodcorrosivity test ofsectionsainternal metallic pipes (coupon)10 to 182. referenced documents2.1 astm standards:a 120 specification for pipe, steel, black and hot-dipped zinc-coated (galvanized) welded and seamless, for or- dinary use3d 1129 terminology relating to water4d 1193 specification for reagent water4d 2331 practices for preparation and preliminary testing ofwater-formed deposits53. terminology3.1 definitions: for definitions of terms used in these testbcity and building distribution water(1, 2, 3, 4, 5)219 to 30methods, refer to terminology d 1129.1.3 test method a employs flat, rectangular-shaped metalcoupons which are mounted on pipe plugs and exposed to the water flowing in metal piping in municipal, building, and industrial water systems.1.4 test method b employs removable, tared pipe inserts which are installed in a plastic piping assembly tailored to provide the same surface and flow conditions as in a normal metal piping system. proper dimensions are provided through- out so that streamline flow (no-flow distortion) results and corrosion and scale formed on the inserts will be the same as that occurring in the metal piping system being tested. steel, galvanized steel, and soldered copper and copper inserts have been found to provide meaningful corrosion test results by this test method.1.5 this standard does not purport to address all of the safety concerns, if any, associated with its use. it is the responsibility of the user of this standard to establish appro- priate safety and health practices and determine the applica- bility of regulatory limitations prior to use. for a specific hazard statement, see 26.1.1.1 these test methods are under the jurisdiction of astm committee d-19 on water and are the direct responsibility of subcommittee d19.03 on sampling of water and water-formed deposits, and surveillance of water.current edition approved april 15, 1994. published june 1994. originally published as d 2688 69. last previous edition d 2688 92.2 the boldface numbers in parentheses refer to the list of references at the end ofthis standard.4. significance and use4.1 since the two tendencies are inseparable for a metal to corrode and for water and the materials it contains to promote or inhibit corrosion, the corrosiveness of a material or the corrosivity of water must be determined in relative, rather than absolute, terms. the tendency for a material to corrode is normally determined by measuring its rate of corrosion and comparing it with the corrosion rates of other materials in the same water environment. conversely, the relative corrosivity of water may be determined by comparing the corrosion rate ofa material in the water with the corrosion rates of the same material in other waters. such tests are useful, for example, for evaluating the effects of corrosion inhibitors on the corrosivity of water. although these test methods are intended to deter- mine the corrosivity of water, they are equally useful for determining corrosiveness and corrosion rate of materials.5. composition of specimens5.1 the specimens shall be similar in composition to the piping in the system in which the corrosion test is being made. welded or seamless pipe shall be used in test method b; however, butt-welded piping specimens may be used in test3 discontinued 1988 (replaced by a 53)see 1988 annual book of astm standards, vol 01.01.4 annual book of astm standards, vol 11.01.5 annual book of astm standards, vol 11.02.copyright astm international, 100 barr harbor drive, po box c700, west conshohocken, pa 19428-2959, united states.1d 2688 94 (1999)e1method b provided care is taken to pick smooth specimens(excluding butt joints).6. effect of cold working on corrosion6.1 cold working can be important in causing localized corrosion; however, plastic deformation can be minimized in specimen preparation by following proper machining practices(6) (for example, drilling, reaming, and cutting specimens for test method a). while the importance of proper preparation and machining is recognized in the other test methods, it is considered important to retain stressed areas in the piping inserts (test method b) since these specimens then have the same properties as the piping system being tested.7. types of corrosion7.1 general corrosion is characterized by uniform attack of the metal over the entire surface.7.2 pitting is a form of localized corrosion, the depth, number, size, shape, and distribution of pits being pertinent characteristics. it may be evaluated by counting the number, by noting the size, shape, and distribution, and by measuring the depth of pits in representative areas. both sides of the coupons must be examined in test method a. in test method b the specimens must be cut longitudinally before internal examina- tion for pitting can be performed.7.2.1 a system may be devised for grading pitting (7).7.3 crevice corrosion is a pertinent factor to consider in corrosion testing, since active corrosion sites may develop in such locations. crevices may exist at threads and joints and under deposits, as well as in corrosion specimens. in test method a, crevice corrosion may be in evidence where the specimen is fastened to the holder and at coupon markings. providing a large specimen surface area relative to the crevice area reduces this influence on the overall corrosion results. light sanding is necessary to remove edges of coupon mark- ing. in test method b, areas subject to crevice corrosion are coated with paint.7.4 edge corrosion the increased corrosion that occurs at edges of corrosion specimens, where the metal may be of different composition or structure, must be given attention. in test method a, specimens of a high ratio of surface area to edge area reduce this effect. in test method b, the edges are painted to prevent fluid contact. if an abnormally high degree of edge corrosion is observed in the case of test method a, the effect may be evaluated by measurement of the specimen dimensions previous to and following exposure. use of a specimen of less thickness may also reduce the edge effect in weight loss.8. water-formed deposits8.1 water-formed deposits observed on the specimens may be analyzed by the methods listed in practices d 2331. the most common constituents will be calcium, magnesium, alu- minum, zinc, copper, iron, carbonate, phosphate, sulfate, chlo- ride, and silica.9. purity of reagents9.1 reagent grade chemicals shall be used in all tests. unless otherwise indicated, it is intended that all reagents shall conform to the specifications of the committee on analytical reagents of the american chemical society, where such specifications are available.6 other grades may be used, pro- vided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.9.2 purity of water unless otherwise indicated, refer- ences to water shall be understood to mean reagent water conforming to type iii of specification d 1193.test method acoupon10. summary of test method10.1 carefully prepared, weighed metal coupons are in- stalled in contact with flowing cooling water for a measured length of time. after removal from the system, these coupons are examined, cleaned, and reweighed. the corrosivity and fouling characteristics of the water are determined from the difference in weight, the depth and distribution of pits, and the weight and characteristics of the foreign matter on the coupons.11. interferences11.1 deviation in metal composition or surface preparation of the coupons may influence the precision of the results.11.2 the presence of different metals in close proximity to the coupon, (within 76 mm (3 in.), even if they are insulated from the coupon, constitutes a source of error in the results.11.3 deviations in the velocity and direction of flow past the coupons may influence the precision of the results.11.4 results are directly comparable only for the water temperature to which the coupon is exposed.11.5 crevices, deposits, or biological growths may affect local corrosivity; results should therefore be interpreted with caution.12. apparatus12.1 coupon specimens prepare coupons in accordance with section 14.7.5 impingement attack (erosion-corrosion), associated with turbulent and high-velocity flow, particularly when softmetals and copper are involved, is characterized by continuous broader-type pits and bright metal from which protective films have been scoured away. some under-cutting also may be present.6 reagent chemicals, american chemical society specifications, americanchemical society, washington, dc. for suggestions on the testing of reagents not listed by the american chemical society, see analar standards for laboratory chemicals, bdh ltd., poole, dorset, u.k., and the united states pharmacopeia and national formulary, u.s. pharmacopeial convention, inc. (uspc), rockville, md.2d 2688 94 (1999)e1fig. 1 installation of corrosion coupons12.2 insulating washer, screw, and nutuse for attachingthe coupon to the phenolic rod. the insulating washer has a sleeve that fits into the coupon hole and around the screw.7,812.3 phenolic rod use a 152-mm (6-in.) length of canvas-based 13-mm (0.5-in.) outside diameter phenolic rod, or equivalent, attached at one end to a drilled pipe plug, and having a flat surface and a hole at the other end suitable for attachment of the coupon.912.4 piping arrangement, as illustrated in fig. 1, for instal- lation of coupon specimens. this arrangement has been changed in order that flow passes over the holder end of the7 allied industrial electronics, 100 n. western ave., chicago, il 60680, extruded fiber washer for no. 8 screw, part no. 26d-3226, manufactured by g. c. electronics, rockford, il (as part no. 6526c), has been found satisfactory for this purpose. the dimensions are as follows: outside diameter 9.5 mm (38 in.), inside diameter of hole 4.0 mm (532 in.), total thickness including the raised are approximately 1.5 mm (116 in.), outside diameter of raised are 6.4 mm (14 in.), and thickness of raised are approximately 0.4 mm (164 in.).8 it may be preferred to obtain the complete corrosion tester and coupons frommetal samples, p.o. box 8, mumford, al 36268, who construct the rod from tfe-fluorocarbon or nylon, include a screw made from this same material and avoid the necessity of including a washer and nut by providing screw threads in the mounting.9 phenolic rod meeting the national electrical manufacturers association(nema) grade ce or le is satisfactory. the pipe plug is marked externally to permit orientation of the coupon as desired.specimens first at two locations and over the specimen first atthe other two locations. this enables one to determine whether the turbulence provided by the corrosion testers or the elbows influences the results.12.5 dial depth gage a gage with a knife-edge base, pointed probe, and dial indicator for measurement of pit depth.12.6 emery paper, number 0.13. reagents and materials13.1 benzene.13.2 chromic acid-phosphoric acid solutiondissolve 30g of chromic acid (chromium trioxide, cro 3) in approximately500 ml of water and add 36 ml of phosphoric acid (h3po435 %). dilute the resulting solution to 1l.13.3 chromium trioxide (cro3), anhydrous crystals.13.4 corrosion inhibitor i, a liquid material having a flashpoint of 71f, which contains amino ketones of rosin, surface active agents, alcohols, and less than 10 % by volume of synergists, for hydrochloric acid.13.5 corrosion inhibitor ii, a nonflammable liquid contain- ing heterocyclic nitrogen bases (usually in the form of salts), surface active agents, and synergists, for sulfuric acid.13.6 hydrochloric acid (1 + 4)mix 1 volume of concen- trated hcl (sp gr 1.19) with 4 volumes of water.3d 2688 94 (1999)e113.7 hydrochloric acid, inhibitedmixed 357 ml of con-centrated hcl (sp gr 1.19) and 5.0 g of inhibitor (see 13.4). then dilute to 1 l with water.13.8 isopropyl alcohol.13.9 methyl orange indicator solution (0.5 g/l)dissolve0.05 g of methyl orange in water and dilute to 100 ml with water.13.10 nitric acid-dichromate solutionmix 224 ml ofhno3 (sp gr 1.42) with twice the volume of water. add 22.75g of sodium dichromate (na2cr 2o7h2o) and dissolve. dilutethe resulting solution to 1 l.13.11 sulfuric acid, inhibitedslowly add 29 ml of h2so4 (sp gr 1.84) to approximately 500 ml of water. add and dissolve 0.5 g of inhibitor ii (see 13.5). dilute the resulting solution to 1 l with water.13.12 trichloroethylene.13.13 tripolifinely granulated, porous, siliceous rock; amorphous silica (sio2), soft, porous, and free of sharp edges or other suitable erosive-type cleaning agent.13.14 vapor phase inhibitor paper.14. coupon preparation14.1 in this procedure, coupons are to be made principally from sheet metal; however, in a few cases, as with cast iron or cast bronze, it may be necessary to prepare coupons from castings.14.2 use a coupon size of 13 by 76 by 1.6 mm (0.5 by 3.0 by 0.0625 in.) for all sheet metals; and a 13 by 76 by 3 mm (0.5 by 3.0 by 0.125 in.) for cast metals. other sizes are suitable, providing the total area is about 259 mm2(4 in.2), the principal requirement being to keep the flat area large compared to the edge area.14.3 sheet metal coupon preparationobtain sheet metal of the type desired except for stainless steel; use cold-rolled steel free of rust spots for ferrous metal. obtain stainless steel with a no. 4 finish.1014.3.1 shear 14-gage sheet metal material to the dimensions of 13 by 75 mm (0.5 by 3.0 in.).14.3.2 drill or punch a 5-mm (0.019-in.) hole with its center about 3 mm (18 in.) from one end of the coupon.14.3.3 deburr all sharp edges on the coupon specimen usinga file or emery belt, and deburr the hole with an oversize drill.14.3.4 stamp identifying numbers or letters on the coupon area below the mounting hole.14.4 cast metal coupon preparationobtain rough cast- ings of the desired metal, measuring about 19 by 114 by 6 mm(34 by 412 by 14 in.) from a commercial foundry or elsewhere.14.4.1 surface grind to the dimensions of 13 by 102 by 3mm (0.5 by 4.0 by 0.125 in.) and a surface roughness of about124 in.14.4.2 drill a 7-mm (932-in.) hole with its center about 8mm (516 in.) from one end of the coupon.14.4.3 deburr all sharp edges on the coupon specimen usinga file or emery belt, and deburr the hole with an oversize drill.10 metals handbook, vol 1, american society for metals, metals park, oh44073, 1961, p. 430.14.4.4 stamp identifying numbers or letters on the smallcoupon area between the edge and the mounting hole.14.4.5 the approximate weight of metal coupons, g, is as follows:steel10.35cast iron11.65copper13.33zinc8.7lead16.6014.5 cleaning ferrous metal couponsremove oil by immersion in benzene. dry. immerse in a solution containing hcl (1 + 4) for 30 min at room temperature.14.5.1 remove acid from the coupon by three rapid succes- sive rinses in separate water baths; the last rinse water bath shall contain methyl orange solution and must be kept neutral(yellow). the first and second bath must be renewed fre- quently. rinse successively in isopropyl alcohol and benzene, and dry with a clean cloth. store in a desiccator.14.6 cleaning copper, brass, and cup