Molten lead-antimony and lead-antimony-tin alloys were spiat quenched in the spinning wheel sel up

under overhead pressure of 703 g/sq.cm. for preparation of ribbons. Physical properties of ribbons such

as density, microhardness, thickness, electrical resistance and melting point were determined. The

corrosion resislance properties of the ribbon and bulk alloy were delermined by weight loss after

immersion in corrosive electrolyte. The potenlial-lime and galvanoslatic measurements of these ribbons in

3 % NaCl solulions were carried ou

Guruviah, S.

Mukherjee, D.

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Bulletin of Electrochemistry 1 (6) Nov. - Dec. 1985. pp. 539-541 PHYSICAL AND CORROSION - RESISTANT PROPERTIES OF RAPIDLY QUENCHED LEAD-ANTIMONY AND LEAD-ANTIMONY-TIN ALLOYS D MUKHEWEE and S GURUVIAH Central Electrochemical Research Institute, Karaikudi - 623 006 ABSTRACT Molten lead-antimony and lead-antimony-tin alloys were spiat quenched in the spinning wheel sel up under overhead pressure of 703 g/sq.cm. for preparation of ribbons. Physical properties of ribbons such as density, microhardness, thickness, electrical resistance and melting point were determined. The corrosion resislance properties of the ribbon and bulk alloy were delermined by weight loss after immersion in corrosive electrolyte. The potenlial-lime and galvanoslatic measurements of these ribbons in 3 % NaCl solulions were carried oul. Key words : Lead-antimony alloy, leadantimony-tin alloy, rapld quenching method INTRODUCTION L ead-antimony alloys are widely used in batteries. The metastable alloys are finding application in many industries like electronics and electrochemicals, etc. Rapidly quenched metallic ribbons are normally associated with metastable phases. Lead-antimony alloy ribbon is reported [ I ]  to show metastable phases at mom temperature. Some of the metastable phases in Pb-Sb and Pb-Sn systems have also been reported [2-61 to be retained at room temperature. It is to be noted that the metastable phases do  not have low free energies, but owe their existence to a process of kinetic inhibition. Such phases, stable at room temperature, have also been observed in Pb-Bi system [7,8]. Earlier studies 19-lo] on Pb-Sb and Pb-Sb-Sn ribbons have shown that rapid quenching increases the corrosion-resistance properties considerably. It has also been shown that thermal ageingat alow temperature increases the corrosion-resistance properties due to certain precipitation effects IlO]. The role of alloying addition on the physical and chemical properties of the ribbons is further investigated here. EXPERIMENTAL a) Materials Pure metals like Pb, Sb, Sn, Cu, Ni, Cd, Fe, Si, Al, Cr used in the study were of 99.9% purity. Bismuth nitrate, sodium hypophosphite, sodium borohydride, which were used as impurity sources during melting were of L.R. quality. Small specimens of ribbons coated on top and bottom cross sectional area with bees wax resin so as to expose one sq. cm. area were used for both the potential-time study and galvanostatic anodic polarization in 3 %  NaCl solution. b) Corrosion tests Coupons were immersed for 45 mins. in 50 ml of HCI : HNOB mixture, where the concentrations of both HCI and HNO,, are kept at 5 %  (v/v), and the corrosion rates determiner' on weight loss basis after cleaning them in distilled water. c) Melting of massiue/bulk alloy Four Eers of alloys (Table I) had been prepared using the ingredients, mentioned under materials. Melting was conducted in an electric furnace with flux. The alloys were subsequently remelted for further homogenization, before rapid quenching on rotating wheels [IO]. d) Electrochemical menrurements The one sq. cm. area of rapidly quenched alloy was immersed in 3 %  NaCl solution in a beaker and the change in potential with time is recorded with the help of VTVM under galvanostatic anodic polarisation conditions. e) De t e rmi~ t ion  of physical properlies The structure of the alloy was determined by X-ray diffraction. The surface characteristic property was examined by SEM (200 to 10000). The composition of the alloys was determined by atomic absorption spectrophotometry. The thickness of the ribbon was determined by digital micrometer. The density and m.p. of the alloy were also determined. The microhardness measurements were done using Vickers Hardness Tester at a test load of 5gm. RESULTS AND DISCUSSION Table I shows the chemical composition of the lead alloy ribbons and the corrosion rate in HCI : HNO:, mixture in the bulk and ribbon states. It is seen from the Table that there was a marked decrease in corrosion rate values in the case of Pb-Sb ribbons while those containing alloying additions revealed marginal reduction. The 80  Pb : 20 Sb ribbon showed lower corrosion rate than other alloys. Table I : Percentage composition of the alloys and their corrosion rate values as cast  (bulk or  massive alloy) and ribbon state Corrosion rate values (g/cm2) x 10-* No. P xentage  composition of the alloy -- Bulk/ Ribbon Massive 1 .  80 P b - 2 0 S b  0.229 0.050 2. 85 Pb - 1.5 Sb 0.22.5 0.100 3. 80Pb- l9Sb-0 .17Cu-0 .13Ni-O.O9 Cd - 0.0 1 Fe - 0.004 A1 - 0.02 Si - 0.002 Cr - 0.07 P - 0.07 B - 0.004 Bi 0.180 0.130 4. 80 Pb-  I0 S b -  10 Sn 0.250 0.200 Mukherjee and Guruviah- Physical and corrosion resistant properties of rapidly quenched PbSb and Pb-Sb-Sn alloys Table II : Physical properties Density Hardness Melting Thickness Alloy No. (g1c.c.) (kdmm2) point (OC) ( m )  (See Tablef) Bulk Ribbon Bulk Ribbon Bulk Ribbon Ribbon 1 6.55 3.365 12.25 12.25 250 Slightly affe- cted at 4W°C 29.4 2 6.75 3.925 9.25 12.25 240 Becamebrittle 36.25 at 4W°C 3 6.025 4.1 15 14.25 8.25 250 Not affected 33.4 at 4W°C Table I1 shows the physical properties of the Pb-Sb  bulk alloys and ribbons. It was seen that density differs marginally in the ribbon state. Reduction in density was more in the case of ribbons of 80 Pb : 20 Sb  and 85  Pb : 15 Sb. Ribbon containing impurity elements decreased in hardness while it was only marginal in the case of 80  Pb : 20 Sb and 85  Pb : 15 Sb  ribbons. In the case of Pb : Sb : Sn ribbon, there was considerable increase in hardness, probably due to some intermetallic formation of tin. The reduction in the hardness of the impurity-doped ribbonsmight beattributed to the layer formation tendency and consequent segregation of impurity and Sb  in the layer zones. It was also seen that the introduction of alloying elements like Sn, Cu, Fe, Ni, Cd, Sr, Al, P, B, Bi, Cr etc. in P b - S b  matrix improved the high temperature resistance of these ribbons. These ribbons were not affected even at a temperature of 400°C. It had also been observed that the appearance of layer structure became more pronounced as the Pb-  Sb  matrix was being doped with various impurity elements (Table 111) (Figs. 1 and 2). Table 111 : SEM Microstructure of R. Q. Ribbon Alloy No. Microstructure/ R. Q. Ribbons (See Table I) 3 Homogeneous matrix is observed. layer structure is prominent. It reveals segregated impurity doped zones (Fig. 1) 1000 x 4 Homogeneous matrix is observed. Layer structure is prominently displayed. It reveals zones enriched in the third alloying element (Fig. 2) 200 x Fig. 2 :  Lead-Antimony-tin alloy Ribbon x 200x The potential-time graph of these alloys and ribbons immersed in 3% NaCl solution are given in Fig. 3. A- '-2j/ - cr bLLOV A Y RIBBON 1 MbSSNC I l? - 1  - b L L O Y R l B W M  1 ALLOY R l b W N  s - A L L O V R l B W N  4 Fig. 3 : Potential vs times in 3 %  NaCl solut~on It was seen that the 80  Pb : 20 S b  ribbon shows more positive value to the bulk alloy. Out of all the ribbons, the 80 Pb : 20 Sb  alloy showed more positive potential than other alloys. The addition of impurities in the Pb : Sb matrix did not change the potential values appreciably. The galvanostatic anodic polarisation studies of the ribbons and alloys in 3 % NaCl solution are given in Fig. 4 and it may be seen that all the alloys showed very little polarisation. Fig. 4 :  Galvanostatic anodic polarization In 3 %  NaCl solutton The Pb-Sb-Sn ribbon revealed much'higher negative potential than the Pb : Sb ribbon having no impurity. The 80 Pb : 20 Sb  ribbon showed positive potential and the change of potential with current w.a little. Fig. 1 : Lead + Antimony + Impurity doped. 1000 x 540 Bulletin of Electrochemistry 1 (6) Nov.-Dec. 1985 . Mukherjee and Guruviah- Physical and corrosion resistant properties of rapidly quenched PbSb and PbSbSn alloys The study revealed that impurity doping in the bulk alloy of 80 Pb : 20 Sb did not result in appreciable improvement in the corrosion resistance of these ribbons except the increase in layer formation tendency after splat cooling. The 80 Pb - 20 Sb ribbon appeared+o be the most corrosion-resistant of the four ribbons prepared and studied. Rapid quenching increased corrosion resistance of bulk 80Pb: 20Sb alloy. The thermal stability of the ribbons were increased as a result of impurity doping. Acknowledgement The authors thank Sri N. Rangarajan, Scientist, for his help in the study. Reference. 1. C B Guitier, B C Git-wen and N J Grant, J Chem Phys, (1 968) 1905 2. BC Giessen, M Moms and NJ Grant, Trans Mat Soc, AIM& 239 (1 967) 883 3. t R Anantharaman, H C Luo and W Klement, Jr, Trans Mat Soc, AIM& 2! (1965) 2014 4. R C Ruhl, B C Giessen, M Cohen and N J Grant, Acta Met, 15 ( 1  967) 19( 5. H V  Hofe and H Hanemann, Z Mat, 32 (1940) 112 6. W Klement, Jr, J Chem Phys, 38 (1963) 298 7. C S Barret and T Massalski, Structure of MetaL, Mc Graw Hill Book C New York, 3rd Edition (1966) p. 233 8. V Heine and D Weaire, Phys Rev, 152 (1966) 603 9. D Mukhe rjee, S Mohan, R Arghode, S Gumviah, R Radhakrishnan ru KS Rajagopalan, Proc Symp Advances in Corrosion Control, Karaiku (1982) p. 2 10. D Mukherjee, R Arghode, S G u ~ v i a h  and KS Rajagopalan, Trd SAEST, 19-2 (1984) 160 Use SPIC UREA DAP for Bumper Harvests Southern Pertrochemical Industries Corporation Ltd. Principal Office : 97. Mount Road MADRAS - 600 032. Factory Site : Spic Nagar. TUTlCORlN - 628 005. 

Physical and corrosion resistant properties of rapidly quenched lead-antimony and lead-antimony-tin alloys

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