1204
INDUSTRIAL AND ENGINEERING CHEMISTRY
towers and shows the operating Luriditions for units producing commercial acids u p to 35 weight 70hydrochloric acid. The call for hydrofluoric acid and fluoride salts created by the increased production of Freon, aviation gasoline, an aluminum for war purposes was also instrumental in establishing broader applications for impervious graphite. Callaham (9) reports the use of Karbate coolers and pumps in the manufacture of hydrofluoric acid, and presents a corrosion table showing that carbon and graphite materials have excellent resistance to the action of hydrofluoric acid of less than 65% concentration, soluble acid fluorides, hydrofluosilicic acid, and soluble silicofluorides. The new fluoborate plating solutions are a postwar application for Karbate equipment. With the petroleum industry moving into the field of chemical> production, corrosion problems have assumed serious importance in many refineries. Operators of a sulfuric acid plant in conjunction with a large oil refinery report (13) that impervious graphite piping was selected and installed after a variety of materials had been tested for over two years. The use of impervious graphite bayonet heaters in a new acid sludge circulating and heating plant at Union Oil Company is described in a recent article (4). Plate $ewers employed in certain refinery by-product processes are subject to annoying corrosion, Trays and bubble caps of both regu>!ar and impervious graphite appear to be a satisfactory solution. A recent publication (2) describes the use of impervious graphite ‘LO resist the corrosive and erosive conditions found in chemical tindustry ejectors. The suction chamber, steam nozzle, and diffuser are fabricated from impervious graphite and mounted in a Nuitable metal assembly. Similar examples of mechanical applications of interest to the chemical industry are bearings, mechanical pump seals, bushings, guide rolls, meter parts, etc., made of either the regular or impervious forms of carbon and graphite LITERATURE CITED
(1) Anonymous, Heat Eng., 20,No.3,188 (1945) (2) Anonymous, Ibid., 21. No. 8. 151 (19461.
-C. L. BULOW.
Vol. 39, No. 10
13) Anonymous, Iron Steel Engr., 21, No. 12, iU5 (1944). (4) Anonymous, Petroleum Refiner, 26,No. 3,138 (1947) (5) Badger, W.L.. Chem. Ind.. 57. No. 5. 858 (1945). ‘6) Be&, J. H., and Gloster,’A. J., Chem. Eng. Progress, 43, No. 5 , 226 (1947). (7) Bonilla, C . P., Chem. Inds., 57,No.5,857 (1945). (8) Burke, J. F.,and Mantius, E., Chem. Eng. Progresa, 43, No. 6, 237 (1947). (9) Callaham, J. R.,Chem. & Met. Eng., 52,No.3, 94 (1945). :.lo)Chenicek, J. A, Iverson, J. O., Sutherland, R. E., and Weinert, P. C,., Chem. Eng. Progress, 43, No.5,210 (1947). 111) De Becze, G..and Liebmann, A. J., IND. ENG.CHEM.,36, 882 (1944). ..12)Dorcas, M . J., Gas, 21, No. 6,38 (1945). (13) Fetter, E. C.,Chem. & Met. Eng., 52,No.4, 171 (19451 (14) Ford, C. E.,Chem. Eng., 54,No. 1, 92 (1947). (15) Ford, C. E., Ibid., 54,No. 2, 132 (1947). (16) Ford, C.E.,Corrosion, 2,No.4,219 (1946). (17) Gartland, J. W., Trans. Am. EEectrochem. SOC.,88, 121 (1945). (18) Hatfield, >I. R., IND.Ex+.CHEM.,31, 1419 (1939). (191 Hatfield, M.R., and Ford, C. E., Trans. Bm. Inst. Chem. Engre.. 42, No. 1, 121 (1946). (90) Heise, G. W., Trans. Am. Electrochem. Soc., 74, 365 (1938). (21) Janes, M., Ibid., 75,147 (1940). (22) Kroll, W. J., Schlechten, -4.W., and Y’erkes, L. A., Ibid., Preprint 89-2 (1946). (23) Lippman, A,, Chem. & Met. Eng., 52, No.3, 112 (1945). (241 Mantell, C. L., “Industrial Carbon,” 2nd ed., New York. D. Van Nostrand Co., 1946. (25) Solan, V. J., Blast Furnace Steel Plant, 35,So. 4,454 (1947). (26) Ollinger, C.G., Chem. Inds., 54, No.5,683 (1944). (27) Poland, F. F., Muterials & Methods, 23, No.3,710 (1946). ‘28) Smyth, H.D., “Atomic Energy for Military Purposes,” Prinrrton, Princeton University Press, 1945,. ,29)Stark, W. H.,Kolachov, P. J., and Wilkie, H. F., ,4772. SOC. Brewing Chemists, Proc. of 4th annual Meeting, 1941,49. ,.30)Tucker, E. F.,and Werking, L. C., Paper Ind. and Paper World. 28, No. 1, 60 (1946). :31) Unger, E. D.,Stark, TV. H., Scalf, R. E.. and Kolachov, P. J.. IND.ENG.CHEM.,34, 1402 (1942). ,32) Vosburgh, F.J., Steel, 109, No. 11, 66 (1941:. :33) Walthall, J. H., Miller, P., and Striplin. M . M., Trans. Am. Inst. Chem. Engrs., 41, 53 (1945). 141 Winslow, N.M.. Trans. Am. Electrochey. Snc.. 80, 121 (1941)
Wrought Copper and Copper Base Alloys
-
Bridgeport
Brass Company. Bridgeport, Conn
S
INCE pure copper
i 3 relatively soft and weak, it is seldom used for its mechanical properties in the construction of chemical equipment. For this purpose stronger yet corrosionresisting copper-base alloys are used. Copper and copper alloys are utilized in the chemical industry primarily because of their ( a ) corrosion resistance, ( b ) ductility and ease of fabrication, ( c ) heat conductivity ( d ) electrical conductivity. and ( e ) mechanical properties. The corrosion resistance of copper and copper alloys to fresh water, sea water, numerous liquids and gases, and the atmosphere accounts for its rapidly increasing utilization in the form of pipe lines, tanks, heat exchangers, etc. The wide use of copper and copper alloys is influenced by their moderate cost and great ease of fabrication into desired shapes. These alloys are supplied in a variety of commercial shapes such as sheet, rod, wire, and tubing, which are generally ductile and are well suited for applications requiring extensive cold or hot working, such as stamping, deep drawing, cupping, spinning, bending, forming, etc. Their high
heat conductivity is of particular iniportttiice, and accounts for the wide use of copper and copper alloys in applications dealing with rapid heat transfer, such as is required in heat exchangers, condensers, water heaters, radiators, and refrigerating and air conditioning equipment. The electrical conductivity of copper and certain copper alloys is of prime importance in electrical a p plications. MECHANICAL PROPERTIES
Bpproxiniately ten copper alloy systems are in commercial U Y today (Table I). Years ago Campbell (12) described hundreds of modifications or variations of these alloys. Many of the modifications in Campbell’s list render them unsuitable for cold working but result in excellent castings with high tensile strength. The present paper is concerned only with wrought copper-base alloys. Table I1 gives the nominal compositions, specifications, and typicaI uses of a fairly representative cross section of commercial wrought copper-base alloys of particular int’erestt o the chemi-
~
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Jcrober 1943
.ai and allied industrm. Table I11 lists the physical properties ,t' the same group of alloys. The effect of alloying and cold working on copper and copper5ase alloys is clearly brought out in Table IV, which shows that ;he copper-bw alloys are usuallj considerably harder and
1. COUMERCIAL STROEGHT COPPER-BASE ALLOYS Copper (various types) 3. Copper-aluminalloys (aluminum bronzea) 3. Copper-aluminum-silicon slloys (aluminum-silicon bronzes %.Copper-beryllium alloys (beryllium copper) 5 . Copper-nickel alloys (cupronickel) 3 , Copper-nickel-zinc alloys (nickel silverj ?. Copper-silicon alloys (silicon bronzes: 3. Copper-tin alloys (tin bronzes) d. Copper-zinc alloys (brasses) LO. Copper-zinc-aluminum alloys (aluminum brsssj ~ 1 . Copper-zinc-tin alloys (admiralty and naval brass) r.4BLE
_.
TABLE
11.
c OMPOzITIONS,
1205
stronger than copper in the annealed condition. Table IV also indicates the extent of hardening and strengthening brought about by cold working. Cold-worked copper and ropper-base alloys can readily be annealed (softened) at moderately high temperatures. The temperature ranges for commercial annealing w e given in Table IV. .ictually the softening effect varies with temperature and time. ibnormally low temperature annealing requires long periods of -ime, as shown by Pilling and Halliwell(69). They reported that .he amount of softening produced in cold-worked copper in 12 minutes a t 300" C. would take 10.4 days a t 200" C. and an estimated 300 years at 100' C. On the other hand, few commercial copper-base alloys can be hardened by heat treatment. Beryllium copper is outstanding because of this characteristic. 4 R-ealth of information has been published on the mechanical oropertiee of copper and copper-base alloys by the Sational
SPECIFICATIONS, .4ND Z'aES OF CO>fUERCIAL R R O U G H T COPPER-RAPE -4LLOYB
__
Xearest .4pplicable A.S.T.M. Specification for Forms Bvailable rypical bsea . Sheet in Chemical Plantb Rod Wire Tube Pipe B-48 B-124 $12 B-124 412 B-1. B - 2 , 8 - 3 , B-188 9-188 Gaskets, electrical equipment, rivets, cotter pins, B-i33, B-i52-A: B-133, B - l e i B-33. B-47, anodes, chem. procese B-187 8 - 4 4 , B-189 equipment, kettles, pans; vats, tanks Condenser evaporator & 3e"xdired copper 99.94 Cu + 0 02 P B-124 112, B-133, B-124 -12 B-68-B, n-42 B-152-B R-133 B-75-B, B-88, h e a t exchanger tubes,' distillery & brewery tubes, 3-111 pulp & paper lines, steam water lines, oil coolefs, .-efrigeration systems, air, asoline, fuel oil, gas. oil, d fl ydraulic lines 8-36 13, B-134 $3 B - I l l , B-135 L3-43 Condenser & heat exchanger 3ed bras* 35 Cu 15 21 tubes, water service lines, f1 flexible hose, pickling :rates, piping, pump lines. etc. bow brasb M-36 04, B-134 14 3-134 24 3ellows, flexible hose, pump YO Cu 20 Zn lines, wire screens fellow brasa 65 Cu 35 Zc €3-36 68, B-134 #7 B-I34 17 8-134 17 . $ . Pins, rivets, screws, springs 90 Cu C 40 Zn R-124 i l Brazing rod, condenser plates, 8-111, B-135 , \ f m t a meta! $5 condenser, evaporator, & heat exchanger tubes, hot iorgings, valve stems, large I I J U & bolts R a d e d hfuntz meta JU Cu + 39 5 Zii t &I71 Condenser tube plateb 0 5 Pb IForging brass 30 Cu 38 Zn B-124 $2 B-124 - 2 Sorgings & hot pressings of all shapes 2 Pb '.Java1 brass 40.0 Cu 39.25 Zn B-21-A, B-124 13 A-121- 4 8-124 #.3 (-ondenser tube plates, weld,ng rod, nuts 8: bolts, C 0 75 Sn atructural parts, rivets, v a l l e stems, tie rods, shafts ondenser evaporator, & tdmiralty brans 71 c'u 28 Zn 1 H-171 .3-!11 Sn 0.04 A s . heat exchanger tubes, conSb, or P denser tube plates, distilleri tubes, ferrules VIanganese bronze P 58.5 C u 39 2 Zii h-124 t4, B-13t4-A lTelding rods, brazing rods 1 Sn 1 Fe -iiluminum brass 'ondenser, evaporator & 1.3 hfn f 7 6 Cu +22 B-111 Zn 2 h l + 0 02 heat exchanger tubes, dis. tillery tubes, ferrules As. Sb, or P hpronickel, 70-3(;. 70 C u 30 Ni 5-11] ,Condenser, evaporator, & heat exchanger tubing, condenser shells & plates, distillery tubes, ferrules High silicon bronze A 97 c u 3 SI 5-96-A, B-97-.4, B-Y8--4, B-124 j-YQ-.h r u t s & bolts, clamps, hardB-98-A, B-100-€3 77 ware, nails, screws, tanks, cable, chem. process e uip p e n t , condenser & %ea; exchanger tubes, wire cloth, kettles screens, screer plates,'shafting r o w rilicon bronze I. 48 I Cu + 1 . 8 $ 1 B-97-B, B-98-B B-98-B R-124 8-99-P FIydraulic pressure linea acrews, nuts & bolts, cable P8 clamps, rivet.s, U-bolts. electrical conduits, welding rod, condenser & heat exchanger tubes, screws Phosphor bronze A , 57, 9.5 ii -- 3 S D 8-103-A 8-130.4 3-1.594 Seater bars, bellows, Bourdon tubing, diaphragms, fasteners. lock washers, sleeve bushings, springs, dectrical equipment, trusk wire, wire brushes. chem hardware, welding rods, perforated sheets. etc. Phospnor bronze C, S%r Y L Llr + 8 bn 13-103-C B-139-C 8-159-c Same as phosphor bronze A Phosphor bronze D , lo,+ 90 Cu 10 Sn B-103-D B-139-D B-159-D Reavy bars & plates for severe compression & wear, springs iluminum bronze 5% 35 Cu -- 5 .I1 B-111 Condenser, evaporator, & heat exchanger tubes, dis. tillery tubes aluminum silicon bronze 91 Cu 7 A1 + B-124 b l l , Nuts & bolts, tie rpds, f o r e ings, pickling equipment 2 SI B-150
Alloy 3iectrolytic tough pitch copper
Sominal Compn., % 99.92 C u 0.04 0
+
+
+
+
.
........
..I
+
+
++
+
+
++
I
j
+ + +
-
-+
.
.
I
1206
INDUSTRIAL AND ENGINEERING CHEMISTRY
Density at M.P., 0 F, 68O F., .Illoy Liquidus Solidus L b . 1 C u . h . 1949 0.322 Electrolytic tough pitc h 8'opper Deoxidized copper 0.323 isio 0.316 Red brass, 85% 1770 0.313 Low brass, 80% 1660 ~.~~ 0.306 Yellow brass, 65% 1650 0.303 Muntz metal, 60% 1630 0.304 Leaded M u n t z metal 1620 0.306 Forging brass 1630 0.304 S a v a l brass 1590 0.302 Manganese bronze A 1650 0.308 1720 Admiralty brass 2140 0.323 2260 Cupronickel, 70% 1780 0.308 1880 High silicon bronze A 1890 0.316 1940 Low silicon bronze B 1750 0.320 1920 Phosphor bronze A 1620 0.318 1880 Phosphor bronze C 1550 1830 0 317 Phosphor bronze D-, 1940 0 295 Aluminum bronze J 1.576 1810 0.278 Aluminum silicon brorlee (7 A I , 2 Si, 91 Cu)
91,.G r . 8.92 8.94 8.75 8.67 8.47 8.39 8.41 8.44 8.41 8.36 8.53 8.94 8.53 8.73 8.86 8.80 8.78 8 16 7.69
Bureau of Standards ( 3 7 ) . Copper and Brass Research Association ( I d ) , Hoyt (23), and Wilkins and Burin (39). The tensile strength of copper and the copper-base alloys drops off a t elevated temperat,ures much more than steel. This generally limits thr use of copper and copper-base alloys to tempcratures belon- 550 600" F. On the other hand, Gillet,te (19) and Mchdam, Geil, and Mebs (g6) showed that the mechanical propwties of copper a i d its alloys are retained a t subatniospheric temperature$, rvhercamany ferrous alloys tend to become brittle (lower impact values). This is of particular importance in selecting materials for haitdling solvents and gases at, suhat~mosphrrictemperatures. Tahll. V summarizes data on thi. auhjcct, taken from Gillette's reporl
(1B). The design engineer must be able t o predict the amouiit uf dvformation which will occur in copper alloys as a function of s t r w and time. The most important properties in this connection a n t.hose relating to creep. Burghoff and Blank (11) rccently COIItributed data regarding the creep characteristics of copper anti some copper alloys a t 300 ', 400", and 500" F. Their data showetl a marked superiority of arsenical copper over the other copper,. tested. The stress for a creep rate of 0.017; per 1000 hours ai 500" F. was 2600 pounds per square inch for arsenical copper as compared with 350-900 pounds for the other coppers. The data presented on the creep strengt,h of admiralty, aluminum brass, red brass, naval brass, phosphor bronze, and 3';1 silicon bronze indicates that the creep behavior of these copper alloys is relatcd with the soft,ening and recrystallization characteristics at, f t i t . testing temperature. The 3 3 silicon bronze and grade ;1phosphor bronze shoTred the highest creep st s i n this group of alloys. T w o new age-hardenable copper-base alloys (Cu-Si-P and CuXi-P-Te) vihich have high resistance to creep are also described. Additional information regarding the creep strength characteristics of copper and copper alloys is given in the Sational Bureau of Standards circular ( S T ) . Vessels complying Lvith the Boiler Code of the American Societ,y of Mechanical Engineers are designed in accordance with the maximum allowable stresses for copper and copper-base a l l o y set up by the .%.S.Sl.E.Boiler Codtl Committee ( 1 ) . Gough and Sopwit,h (20) found that phosphor bronze and aluminum bronze tested under various corrosive conditions showed excellent resistance to corrosion fatigue and compared favorab1)with the stainless steels. More recently Burghoff and Blank (11 ) described the fatigue characteristics of copper and some copper alloys tested in air at room temperature. The fatigue strength for these materials (polished specimens) ranged from 13,000 to 34,000 pounds per square inch a t 100,000,000cycles. The ratios of the fatigue strength to teniile strength rangrd from 0.26 to 0.25. They :tlso showed that the notch sensitivity incrrascd with the notch iharpneGz. .idditicinnl iiiforinxtion (111the fatigw. Qtrengthof cop-
Coefficient of Thermal Expansion per F. f r o m 68-572' F. Y.8 X l o - ' 9 . 8 x 10-6 10.4 x lo-' 1 0 . 6 X 10-6 1 1 . 3 X 10-6 1 1 . 6 x 10-c 1 1 . 6 X 10-6 1 1 . 6 X 10-6 1 1 . 8 X 10-6 1 1 . 8 X 10-5 1 1 . 2 x 10-1 9 . 0 x 10-5 1 0 . 0 x 10-0 9 . 9 x 10-2 9 . 8 x 10-( 10.1 x 10-6 10.2 x 10-0 1 0 . 0 x lo-! 9 . 2 x lo-^
Vol. 39, No. 10
Therlnltl Electrical Properties Conductivity . at 680 F. (.Innealed) a t 68' F., Hesistivity, ConductivB.t.u./B Ft.,' ohms ity, Yo Fr.iHr.?b 1'. :mil ft,.) [..I.C.S. 226 10.3 101 146 12.2 85 42 .~ 28,O 37 81 32.0 :3 2 38.0 67 27 71 87.0 28 71 38.0 28 69 38.0 27 67 40.0 26 61 -13.0 24 64 42.0 25 17 225.0 4.6 21 150.0 7.0 33 S6.0 12 47 18 n8.0 36 13 80.0 29 94.0 11 61.0 46 17 20 130.0 7
pi'[' a r i d i ~ o ~ i p i ~ - l i~a l*l(i~~ hits ys .C, tl.9).
het.ri
hlodulur of Elasticity in Tension, Lb./Sq. In. 17 X 10' 106 17 X 108 16 X 10' 15 x 106 16 x 106 15 X 10' 16 x 1 o e 15 X 106 15 X 106 16 X 10' 22 x 10'. 15 x io& 17 X 10' 16 X 108 16 X 10': 16 X 10' 1 7 . 5 X 10; 1 6 . 5 X 10
prhliehed elsewhere ( 2 4 , 2.i.
FABRICAT103 PR0PF:K'TIES
'Lh; easc: n ith which copper ami various copper alloys C:$IL t ) t " liot'- and cold-vorked, niachincd. welded, brazed, and solderd i,. described in Table I\-. KhiIe copper can be welded by either r h t :trc or oxyacetylene method. tinoxidized or oxygen-free iwpper nliould be used. (Rmluchg gases at elevated temperat,ure lt.;td Io emhrittlement of tough pit,ch copper since it contains cul)i'~)u. oxide IT-hich can be rwluced by hydrogen.) Clauser (1.3) report I on the progress made during the war years in connection x i t h ihl iriert-gas-shic,lded arc ~ e l d i i i gprncchs. Helium \vas originall!iised, but novi argon gas is generally utilized fi;nce it is availa1)lc i ii commercial quantities and shields the d d puddle more c+fei.tively. K i t h the argon gas shield, various brasses, silicon broilat'. cupronicliel, and phosphor bronze can he welded without any f l n u . Copper, hon.ever, cannot bt. \velded hy this process. Priest and G r o w (31) discuawti thP possibilities of the fluoiiiit-hydrogen torch. Thcy reported that its flame welds copper wirll since copper fluoride meltr at a lov,--ertemperature than CUI)per and is therefore self-fluxing. By increasing the fluorine hul). ply a t the moment wlien the copper fused, a cutting action similar to that on steel results in a clean, uniform, knifelike cut on the copper. This is t,he first successful a,ttempt at flame cutting coppvr. Stwl and cast iron equipment can be joined or broken section. repaired more economically and tdYectively by bronze welding. This is done by brazing, since tlrr parent metal is heated to redne.. only and the melted bronze adherr. to it. It avoids expensivt. preheating and possible warping. The combined mechanical a,nd fabrication properties of c0p1)t'i and copper alloys has result e i l in iimicrow applications of thc,il, materials in a wide variety rif form. in chemical plants su1~11 a, those shoivn in Table TI. ( 2 ,
COKROSIO.11 RESISTANCE
'Thr use of metal i n variow media is influenced by a lay'" number of factors 01' c,)uditiona. These factors may function ilk an adverse manner t o shorten tht: useful life of a piece of equipment, or t,hey may lie beneficial in lengthening the service life. Many of the conditions influencing the rate of corrosion or usi' 111 metals in the chemical industry are given in Table VII. Consideration of all of these conditions or factors will aid in the selectioi, of the proper material to use. In addition, consideration of theatfactors may help in explaining mid ovrrc,omiiig difficulties iyhvrr premature failure orctir.~. AQT-IWT-~ C O R R U S I ~ Si.) : i i i : i ~ i ~ :inti Cross ( 1 7 ) demoiistial~~ti ihxt t h r cwrrosion of wipl)t~ri r i :iqueouu sulfuric acid solutirrri~i-
L
dqxndent upon the concentration of dissolved oxygen. Confirming tests conducted on copper in wlfuric acid solution (at room temperature) freed of air by boiling prior to immersion of the test roupons show that practically no corrosion occurred during a period of six months (6). High conccritrations of oxidizing agents, such as ferric and dichromate ions, are coneideral)l>. more active osidiziny agenrs than dissolved osygen in acid solutions. Dissolvrd sulfur d i o d e i u I i i I J r ~ 'tlcrivr' t iiari osygen since it a irig ageni in a riiaiin of carbon diositlv iii :+rid. The pi~i.wncc~ N qucous solutions niay iiicreasc the aoluioii 1;rciducts iv1iic.h USprr-haw alhy-: so that the!- do not. have ail opportunity to stifle tlir corr,)sivcL action. Thr prcsencc 01' hydrogen sulfitli~ in rtqueous solutiom (fresh arid salt waters) acceleratcs the rorrosion of copper and some copper-baw alloys n-ith the formation of voluniinous nonprotective corrosion products (although the sulfides :+re onlj- .lightly .soluble in aqueous solutions). KATURAL K.ITERB. The corrci4vc.nria ~f natural fresh water deperidP iii a CIJIIIplicated iiianner upon the conci.iit ration or mineral matter, gases, organic matter. sand, and debris. TIw sum of all the i ~ions ~ arid t anious give+ the total mineral cwntent of the iratcr 'i~hictiwill vary frorii :iI)prosimately 0.003 u p to 3.5'; for sea \vat PI'. K h c n lieatpd, certwiri water? )Till dcponit thick miner:il w i l r i of variables c.ompositioii 011 t111- iiii..tal surfacw~wit 11 xhirli the ivarvr coiiieh into cc,ritai'l. Tiic. most coninion 1iiiner:il5 1 d e found t i n Ilrat transfer surfaces consists essent islly of c:tlciuni carbonate. Frequently th se mineral scalcs arc very protective t q the miderlyinp tlit.tal. La ~igclirr'sralcium mrhonatt. saturatiori index ( 2 4 ) is a u v fu! ii-w::wr'C: of t l i r h t m d m c y toward sriilirig or corrorion. Rj-zIiar (SS) propci+d R niotiificatioii of Lmgelier'p exprt4oii v a l i i d tlir "atai)ility iiidrs," wliirli lit. - t d tltrough a rtudy of thirt>--Piu fie!d Pon-ell. Racon, and Lill (30) rcvicn-ed the reccnt devclopment in rorrcirion prevention l ~ ycontrolled calritim c.:trbonate scales. I3ulorv ( 9 )sumiiiarized the outctanding corroe :ic.teristics of copper-))a , .ea water and fresh ~vaier. Soft nonsca!e-forniiiig w i t crs arid ,>ea water may lead to cnrrwion failures from lacalizctl ciclzincificatioii C J gcncra! ~ dezincification in the brasses ~:oxttainirig niucli zinc, such as 3Iuntz metal (60 copprr-40 zinc), ~ioninhihitedalumitiuni brass (76 copper-22 zinc-4 aluminuni), and ye!lo\v brass (67 copper-33 zinc.) containing no dezincification inhibitors. Red brass (85 copprr -1.5 zinc.), admiralty (70 coppc.1-29
1208
INDUSTRIAL A N D ENGINEERING CHEMISTRY
TABLEV. PROPERTIE~ OF’ COPPERAND COPPERBLLOYS AT BIJRA’MOSPHBRIC TEMPERATURES (19) -0, A
Copper
Manganese Bronze
.4lunimum Bronze
70-3L Bras.
32,500 50,500
51,500 74,000
72,500 94,500
77,500 96,000
Bl,5OU 73,5@@
8,500 11,500
27,000 32,500
24,000 29,000
26,500 29,000
28,OOL; 30,OOC
48 57.6
25.5 35.5
28
26 28.5
49 t
37
76.5 77
77.5 72
44 41
29 30
7i 75
43
77 85
20 20 5
14 20 5
78.6
80-20 Tensile ,strength, Ib. sq. in. Room temp. -300’ F. Proof stress, lb./sq. in. Room temp. -300’
F.
Elongationin 2 i n . (0.26in -diam. bar), % Room temp. -300’ F. contraction of area, % Room temp. -300’ F. h o d impact value, it.lb Room temp. -300’ F.
/L
Cupronickel
50
74 6
b5.5
zinc-1 tin-O.O5% arsenic or antimony), arsenical aluminum bras? (76 copper-22 zinc-2 alumir1um-O.O5% arsenic) and other copper base alloys generally resist these corrosive waters very well Bulow (10) showed the effect of alloy additions or modificarionk on the corrosion resistance of copper and copper-base alloys toward flowing sea water. According to Tracy and Hungerford (W), addition of iron improves the corrosion resistance of cupronickel alloys markedly toward rapidly moving sea salt solutions. Cuthbertson (16) reported on the corrosion resistance of tit. bronzes and tin-aluminum bronzes toward sea water. ~
FACTORS MFLUENCING CORROSION RATE
Data available from a large number of sources show that in various media and under certain conditions of service, certain factors tend to become very prominent in affecting the suitability of an alloy. For best results it is necessary to consider the possible effect of these various factors (Table VII) when making a finai choice. CAVITATION.Occasionally the hydraulic phenomenon called “cavitation” occurs in centrifugal pumps, hydraulic turbines, and propellers, in the form of pitting in the wake of gates or on the loa pressure side of blades near the trailing edges. This phenomenori applies to the action of water vapor a t a critical temperature and pressure in an enclosed space which is suddenly condensed t o liquid form by increasing pressure with the creation of vacuun: cavities. The collapse of such cavities has been calculated a: producing pressures from 10,000 up to 40,000 pounds per square inch. Russell (32) suggested that the term “implosion,” the opposite of “explosion,” would be a more suitable term to describe cavitation. Vater (38) reported that a propeller bronze (55 copper-35 zinc-3 nickel-2 manganese-1 iron-1 aluminum) and an aluminum-silicon-bronze (90 copper-7 a l u m i n u m - 3 silicon > showed good resistance to cavitation in laboratory tests conducted in fresh water.
CORROSION PRODUCTS, CREVICES,AND POINTSOF CONTACT. Frequently the corrosion products, crevices, and points of contact between materials of construction function in the same manner-namely, in the setting up of a concentration cell, which encourages localized corrosion or pitting. Wyche, Voigt, and LaQw (40) described the nature of corrosion in crevices and suggested various means of preventing crevice corrosion in commercial installations. Bulow (8) also discussed the causes and prevention of crevice corrosion in copper alloys. ELECTRICAL CORONA. In humid atmospheres occasionallv electrical corona may lead to the formation of nitric acid and similar substances which will attack copper-base alloys. The attack is similar to that which occurs in ducts and hoods handling acid vapors. Schilling (54)examined the Mouthal-Iberg high-voltage
Vol. 39, No, 10
transmission line and found that corrosion had reduced the hldre! cable to half its original cross section at the tension towers. He concluded that the difficulties had increased as a result of an increase in operating voltage from 8 to 15 kilovolts, and that thr corrosion was probably due to the intense corona a t the defective insulators which continued to give service since they were s u p ported on wooden toxers. The situation was remedied through overvolt,age protection, etrengt,hened insulators, and replacemeni of defective insulators. ELECTROLYSIS. Eliassen and Goldsmith (18) showed thai aiternating or direct current flowing through a water pipe hae only slight, if any, influence on the extent of corrosion occurring on the inside of the pipe. On the other hand, much informatior, has been published which indicates that deep pitting will occur a t those points where the electric current leaves a metal structure, such as a pipe passing through a wet corrosive soil or a corrosivr solution. Research on external corrosion of pipe lines has resulted in the development of good working theories which have tlided in the development of remedies or means of overcoming iuch corrosion. hiorral and Bray (28) showed that the anodic corrosion of aluminum bronze, silicon bronze, and copper in 2137~ sulfuric acid solution is quite high compared with other mat,erials they investigated the anodic corrosion resistance of sixty-eighi metals and alIoys. EROSION.The presence of the sand, salt, or hard particles i L churning aqueous solutions may cut through corrosion films and lead to high rates of penetration of the metal. The effect may br purely mechanical or a combination of mechanical and corrosior. effects working simultaneously. FRETTISO. Where metal parts are rubbing against one another in such a manner that high tensile or shear stresses result, fretting corrosion may occur, To date the only reported instances of suck corrosion are in leaf type springs, but it, may be more widespread than is conimonly realized. GALVANIC COUPLES. The coupling of copper-base alloys ti each other generally does not lead to a significant increase in corrosion rate. On the other hand, the galvanic coupling of coppei alloys with less noble metals, such as aluminum, steel, zinc, etc.. may lead to serious corrosion of the less noble materials in man) corrosive environments. The seriousness of such a galvanic couple depends not only on the potential difference existing between the two dissimilar materials, but also upon the resist,ivity of the cor-
T ~ B L E1’1.
.~PPLICATIONS OF
COPPER-BASE ALLOYS15
CHEMICAL PLANTS ibsorptlon columns
.igi tators
Air conditioning Air lines Anchor screwn Anodes hutoclares Beater bars .~ Bellow8 Bolts (and nuts) Bourdon tubing Brazing rod Brushes (wire) Bubble caps and trays BUEbars Bushings :slee\e) Butts Cables Castings Chemical hardware Chemical process equigment Cleinps Columns Condenser shells Condenser tubes Condenser tube plates Condenser tube supports Conduits, electrical Conveyers Coolers Dephlegmators Diaphragms Digesters Distiller tubes ~~~
Electrical conduitE Electrodes Evaporator rubes Extractors Fasteners Ferrules Filters Flexible ~~~. hose Forgings, various shapes Fractionating colcruns Gas lines Gasoline lines Hardware (chemical, Heat exchanger tubea Hinges Hose (flqxible) Hydraulic lines Instrument tubing Kettles (plain, j,acketed, and mixing) Lock washers Mixers Sails N u t s (and bolts: Oil coolers Oil lines Pans Perforated plates Pickling baskets Pins Pipe lines Pressings (forgings) Pressure vessels Process equipment, special ~~~
Pulp and paper line? Pump lines, parts, ano rods Radiators, heating Reboilers Refrigerators Retorts Rivets s i r e i n plates Screws Shafting Sleeve bushings Springs Steam lines Stills Structural part6 Tanks Tie rods Towers Trays and bubble cape Treater drums Truss wire Tubing (condenser. heat exchanger, and instrument) Vats Valve bodies I‘alve stems U-bolts Unions and oouplingr Water lines Welding rod Wire Wire brushes Woven wire screen or cloth
October 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE VII. CONDITIONS ISFLUENCING THE RATEOF CORROSION OR USE OF METALS IN CHEMICAL INDUSTRY Catalytic effect on process Cavitation Contamination of product (taste, color, etc.) Composition of gas (pure or mixture, impurities, etc.j Composition of solution (pure or mixture). If a mixture, concentration uf the iollowing items is important: Specific ions Imp& ties Oxygen, oxidiiing agents, hydrogen acceptors, etc. Corrosion inhibitors or accelerators Entrained solids (crystals, debris, sand. etc.) Entrained liquids or gases (second phase) Corrosion-product distribution Crevices or points of contact Electrical corona in gaseous atmospherea Electrolysis Erosion Frerting Galvanic couples Impingement or impact of gas or liquid Pressure Stress Supersonic waves Temperature Yelocity of liquid orgae (rate of supply and distribution of oxygen and oorrosive agents Vibration (corrosion fatigue) welds (soundness, potential, composition a n d structure, etc.).
rosire liquid, the relative areas of the metals involved, and the actual current flowing between two or more parts of the galvanic ceil. The resistivity of fresh water is sufficiently high so that if galvanic corrosion occurs, the attack is usually localized quite near the junction of the two metals. Tracy (86)reported on the corrosion resistance of soldered joints on copper and brass tubes in tap water. In solutions of salts, acids, bases, and sea water of higher electrical conductivity than fresh water, pitting may occur close t o the junction of the two metals or a t some dist'ance away from the point of actual electrical contact. The coupling of copper alloys with iron is quite common in equipment handling fresh water and slightly corrosive liquids. For example, copper and brass t'ubes are frequently used in conjunction with thick, steel tube sheets in heat exchangers where river or lake water is the cooling medium. Steel tubes joined by bronze brazing are used in fresh water. Steel and copper are aoupled together in locomotive boilers. Copper rivets and aluminum, in contact with salt water or marine atmosphere, may cause considerable difficulty. During the war cadmium plating of copper alloy aircraft parts was widely used t o prevent trouble of this kind. Steel couplings, nipples, etc., in contact with long runs of brass piping, may fail in a comparatively short time and should therefore be avoided. IMPISGEYENT OR IXPACT OF GAS OR LIQUID. Localized corrosion of copper and copper-base alloys may sometimes occur at those points where a liquid or gas impinges or strikes the metal, such as in tube and pipe bends, in flow through screens, in area:. where the cross-sectional area of the system is suddenly reduced (from water box to tubes in heat exchangers) and where incoming gases strike against baffles or tubes in heat exchangers. If anot>herphase is present in the stream, such as sand, salt crystals, various debris, gas bubbles, or droplets in a gas stream, the effect of impact on t,he metal surface frequently becomes considerably more serious. Bengough and May ( 4 ) described the appearance of impingement corrosion pits which form in certain copper alloys subjected to impinging streams of water containing bubbles of air. Buloiv (10) reported on the impingement corrosion resistance of thirty copper-base alloys in sea water flowing a t 2 to 3 feet per second, and on the effect of steam impingement' on copper tubing ( 7 ) . PRESSURE.The effect of pressure on corrosion reactions is similar to its effect on other chemical reactions-namely, to increase
1209
ihe mpply of the reacting materials. The increase in the presnurt on such gases a8 oxygen, ammonia, and sulfur dioxide generall? leads to a n increase in the rate of attack on copper in cert,;ain cor. rosive media. A decrease in pressure over a corrosive liquid ma! aid in the removal of the corrosive agent. and a reduction in the rate of attack of the metal. STRESS. The effect of applied (external) stresses or residual 'resulting from cold working) stresses upon copper-base alloy? varies considerably, depending upon the composition of the allo. ttnd the corrosive environinent. It' is evident from the extensive literature on the st,ress corrosion or season cracking of brass& that the presence of ammonia- and nitrogen-bearing materiais 'amines, ammonium sulfate, etc.) plays an importmt part in prd. ducing stress corrosion cracking. Moore, Beckinsale, and Xai. linson (27) have shown that severely stressed brass d l not crack ,. exposed to air from which the common contaminating suhatances had been removed. Croft (16) published an extensivy bibliography on stress corrosion cracking, and additional information \vas presented by several authors at, the Symposium OL Stress-Corrosion Cracking of Metals ( 2 ) . The value of the stresh relief anneal has been known and used in the mpper alloy industry :or many years (26). SL-PERSOSIC WAVES. Hedvall (28) showed that the S U ~ W K . Donic waves generated by yuart.a oscillators markedly increaser: !he corrosion of copper exposed t.0 iodine vapor or sulfur fumes, The effect of temperature on corrosion ratt TEMPERATURE. varies considerably, depending upon the environment, because of che overlapping effect of other factors. I t has been reported (8 Lhat the depth of corrosion occurring under deposits in 3% sodiun. ':hloride solutions will double every 20' over the temperaturrrange 20" to 78" C. On the other hand, if the temperature btamrnes high enough, sufficient air may be expelled from the so!^ rion to l o w r the corrosion rate markedly. When heated, certain waters deposit' thick mineral scales I J I . The hot metal surface. These mineral scales may completsl: protect the underlying metal. Specimens of copper-base alloy? have been examined which were so well protected by carbonat,V xnd siliciltp type scales that they have resisted attack for gent3i-a. tions. The build-up of a thick mineral scale on the surface of a heater lube may icriously interfere with heat transfer. This loss in hea; :r msfer may result in considerably higher metal surface temperarims, with the result that the metal surface facing the fire or hoi \'xpors may rapidly oxidize. Failures resulting from this cause are usually described as failing from overheating or actual burning. Sometimes localized corrosion or pitting occurs on ho., metal surfaces where bubbles of gas separate from t'he liquid The bubbles hinder the water or liquid from cooling the met& burface! and allow local hot spots to form on the metal surface The importance of this factor was brought to light many years agc ay Benedicks (3), who found that submerged, electrically heat& &-iresivould melt locally under bubbles of gas. Various met,horfhave been suggest,ed for overcoming this type of attack. Situations are occasionally encountered where a drop in tenlparature accelerates corrosion more than a rise in temperature this is due to the condenmtion of water vapor on cold metal surfaceb?, The contamination of the condensate by ammonia or nitrogen compounds mag lead to stress-corrosion cracking O: highly stressed brass. The seriousness of this depends upon [ a the amount of ammonia or similar nitrogen compounds preseni in the condensate, (b) the magnitude of the stresses, ( c ) the inherent susceptibility of the alloy t o this specific type of attack. i:di the amount of water vapor, and (e) the amount of air. IL certain types of equipment it is possible to raise the temperat'ure sufficient,lyto prevent condensation or coritamination of t,he condensate and thereby materially lengthen the life of the equipment VIBRATION.The effect of vibration on corrosion is of increasing importance because of the more widespread use of high speed machinery where numerous cycles of stress occur in a very short
1210
INDUSTRIAL AND ENGINEERING CHEMISTRY
-.me. Khile metals subject to repeated stress in air a t rooni ternijerature show a critical value of stress (endurance limit, or fatigue liriiit) below which cracking does not take place over an enormous ,lumber of cycles of stress, this critical value frequently does not appear when the metals are exposed to corrosive environment.. \[-hen alternating stresses are applied in corrosive environments. -he stresses necessary to produce corrosion-fatigue cracking are :iliich loa-er than those needed to produce fatigue cracking. The 4 imiage produced by the simultaneous action of alternating htresc 111 a corrosive agent greatly exceeds that produced by t,he indeIwiidrnt action of these two factors. Haigh (21) found that tlic (itcmaging effect of anininnia on brasses \vas producrd only \vticn 1 he ammonia and alternating stresses Irere simultaiieoudy ap:)lied. I n other media, such as fresh and salt water, the endursi!re limits for brasses and bronzes frequently are only slightl?. ll liver than those found during tests in air. iIeat exchanger or condenser tubes are sometiines subject t o ;,orrosion-fatigue cracking. The design of the unit in which thew Lubes are installed is of prime import,ance. Such failures can l w rccognized from their location. Circumferential crac!;s develop ruidivay between the tube support plates or within 2 inchea [Jft,he -1ibe sheets. Such tube failures generally occur at thow points $:here the steam or vapors enter the heat, exchanger-t,hat is, ill ,iibes facing t,he inlet or vapor lane. While the fatigue c1iarac:.&tics and corrosion resistance of the copper-bast= allo?-s vary, appears that the most satisfactory n a y to conibat corrosion ‘:itigue is through the elimination or reduction of t.hc txstcnt. of ,.ii.lration, rather than through alloy selection. [t is difficult to make sweeping generalizat,ions rrgiirdiiiy tho vrrosion resistance of copper and copper-base alloys since they v:try markedly, depending on the nunierous factors just discussed :,!id the alloy. The rate of attack of all copper-base alloys 111 3trong nitric acid solution is too high to permit their use where,b\.er t,his acid is encountered in moderate to high concentrations. 111 other types of acids the rate of attack is generally asswi:itt=d .\-ith the concentration of oxygen and oxidizing agents. This ~ 1 5 0holds for ammonia-bearing liquors. The copper-base alloys .tiow outstanding resistance to attack by fresh n-ater, sea Imter, ‘iiany acids, bascs, salts, and compounds, numcroui- ga-w, : ~ n d :kif, atmosphere. 1.1
LlTERATURE CITED
Am. SOC. of Mech. Engrs.. Boiler Code, Proc. Am. S O C . J l e c h . Engrs.. 1944. Am. SOC. for Testing Materials-Am. Inst. of Ilining t Met. Ennrs.. on Stress-Corrosion Cracking of Met- “SvmDosium “ . als,” 1945. Benedicks, C., Trans. Am. Inst. J l i n i ~M e t . E’ngrs.. 71, 597626 (1925).
Vol. 39, No. 10
(4) Bengough, G. D., and May, R., J . Inst. Metals, 32, No. 2, 81 256 (1924).
(5) Bridgeport Brass Co., unpublished data. (6) Bulow, C. L., J . A‘eu. England Water Works Assoc., 59, No. 1 163-82 (1945). (7) Bulow, C. L., Metals I% Alloys, Copper Alloy Bull. injert (Dc I 1945). (8) Ibid. (hug., Sept., Oct. 1945). (9) Bulow, C. L., Southern Power and Ind., 64, No. 5 , 54-9, :I\ 11946). (10) Buloq,. C. L., Trans. Electrochem. Soc., 87, 319-52 (1945). (11) Burghoff, H. L., and Blank, A. I., Proc. A m . SOC.Testing J1a1 terials, preprint, June 16-20, 1947. (12) Campbell, William, Ibid.,22, 215-19 (1922). (13) Clauser, H. R., Naterials &. Methods, 25, No. 4, 86-90 (1947). 1
Copper and Brass Research Assoc., “Standard Commerc~,(l Wrought Copper and Copper-Base Alloys,” 2nd ed., 1947. Croft, H. P., Proc. Am. Soc. Testing Materials, 41, 905 (1941, Cuthbertson. J. TT’.. J . Inst. Metals, 72, 317-42 (1946). Damon. G. H . , and Cross, R. C., IXD.E x .CHm.,’28, 231 :< (1936).
Eliassen, R., and Goldsmith, P., J. Sm.
Water W o r k s A4ssoi.., 36, 563 (1944). Gillette, H. W., “Impact Resistance and Tensile Properties
Metals st Subatmospheric Temperatures,” A.S.T.M., 1941 Gough, H. J., and Sopwith, D. G., J . Insf. d f c t a k , 60, 143 (19371 Haigh, B. P., Ibid., 18, 55 (1917). Hedvall. J. .1.,Tek. Tid.,74, 625-6 (1944). Hoyt. S. L., “Metals and Alloys Data Book,” Nerr Yorh. Reinhold Pub. Corp., 1943. Langelier, W. F., J . A m . Water Works Assoc., 28, 1500-1 (1936, McAdani, D. J., Jr., Geil, G. W., and Mebs, It. W., Proc. Am. SOC.Testing Naterials, 45, 448-81 (1945). Moore, H., and Beckinsale, S., J . Inst. Jletals, 23, 225-45 (1920) Moore, H., Beckinsale, S., and Mallinson, C. E., Ibid., 25, 35152 (1921). Morral, F. R., and Bray, J. L., Tram. Electrochem. Soc., 75 427-40 (1939). Pilling. iY.B., and Halliwell, G. P., P r o c . Am. SOC.Testing -If(!temkls, 25, 97-119 (1925). Powell. S.T., Bacon, H. E., and Lill, J. R., ISD.ESG. CHEJ~.. 37, 842-6 (1945). Priest, H. F.,and Grosse, A. V., IbitE., 39, 431-3 (1947). Russell, G. E., J . A‘ew England Water Works Assoc., 99, KC, 6, 295 (1946). Ryznar, J. W., J . A m . Water Works Assoc., 36, 472-83 (1944). Schilling, E., Bull. assoc. suisse elect., 36, 741-4 (1945). Tracy, A. W., Heating, Piping, .4 ir C’onditioning, 14, 5 3 8 - 4 1 (1942). Trac,y, h. IT-., and Hungerford, R. L., Proc. A n . Soc. Testiny dlaterials, 45, 501-612 (1945). U. S. Dept. of Commerce, Xatl. Bur. of Standards, Circ. C-447, 65-160 (Dee. I , 1943). Vater, XI., 3letaiZkunde, 36, 38-43 (1944).
Wilkins, R. 4.,and Bunn, E. S., “Copper and Copper-Basr Alloys,” New York, McGraw-Hill Book Co., 1943. Y’yche, E. H., Voigt, L., and LaQue, F. L., Trans. Electrochem SOC..89, 265-78 (1946).
ASTOMERS
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_ _ I _ _ _
HA41ZRYL. FISHER, I . S. Z r d u s t r i a ! Ch emir&.
rnr.. S t n rnfortl, Coir i t .
VEX before the war the aging arid improved cornpoundiiiy of products of naturalrubber had become so good that rubber was being used by engineers as a durable niateriai of construction and operation. Furthermore, the first conimrrcial synthetic rubber, Thiokol, found early acceptance bccauhe it filled the great need for a rubberlike material n-ith high resistance t o the welling action of gasoline, oils, and fats. Seoprcne followed and quickly found a place for itself because of certain desirable prop-rties, although its price m s several times that of natural rubhcr.
Ikvrlopnierits in the synthetic rubber field came rapidly, :,1!(1 during the Ivar all requirements fort,unately were soon met. Materials that can be stretched to at least double their leiigtil and, when the stress is released, return to ‘their original posit ioii or lcngth quickly or \rit,hina reasonable time-such materials ;?.n rubberlike and in general are included in thc meaning of the tcriri elast,oinc>re. The property of stretching and retraction is :-hu unique characteristic of elastomers, but other properties arc o i interest and use as n-vt~ll. hll these ran be listed as follow:::
