Tin and Its Alloys ROBERT J. NEKERVIS Tin Research Zmtitute, Znc., Columbus, Ohio
P
ERHAPS the most significant development since last year’s summary was the removal of tin from the U. S. Department of Commerce’s restricted list on August 26, 1949. Accordingly, new developments requiring tin, such as alloy coatings and electrically conductive glasses, now have more than just academic interest. In the established fields also, particularly in tin plate, solders, and bronzes, there has been a considerable amount of development.
several new addition agents patented for various tin electrolytes (96,98, 40, 46) and several patents on improvements in tin electroplating apparatus (36,46, 68). Calculation procedures for electrical requirements for electrotinning steel strip have been developed (74). Methods of determining coating weights on electrolytic plate have been published (64). HOT TINNING
Because hotrdip tin plate accounts for about 45% of tin-plate production, it too has received attention. Hot-tinning problem which confront the industry have been discussed by Crombie ($9). Two potential substitutes for palm oil used in hot tinning, a dimer acid and a modified tallow, have been developed (30). Home (44) has written a practical handbook on hot tinning for article and wire tinners. A method for hot-dip tinning zinc die castings permits their use in food and beverage handling (8).
TIN ALLOY PLATING
The Tin Research Institute has come forward with some interesting results with tin-copper, tin-zinc, and tin-cadmium electroplated alloy coatings. Bright speculum (40% tin, 60% copper) defiosita have been obtained (10). Factors influencing bright 01 dull h i a h have been determined by x-ray investigations (89). Electron-diffraction studies of thin copper-tin films have been made in Germany ($7). Production experience and economies obtained in the electrical industry with tin-zinc alloy coatings (tin 75 to SO%, zinc 20 to 25%) have been described by Miller and Cuthberteon (7,9), Excellent steel protection was obtained with coatings in excess of 0.0003 inch. Resistance welding of coated steel with tin-zinc alloy has been evaluated (43). No difficulties were encountered in flash welding; properties were comparable to uncoated sheet. Tin-zinc alloy coats were better suited to spot welding than plain tin coatings. Bennett’s investigation of tin-cadmium alloys (9) has shown that bright deposits may be obtained. Corrosion tests, which are not complete, show that tin-cadmium deposits are a t least equal to equivalent thicknesses of cadmium. Deposits of all ranges of composition were readily solderable. A study of the solderability of electroplated tin-lead alloy coatings has shown that they remained in excellent soldering condition for 9 months, the maximum length of time the tests were run (03). Other tin-lead alloy plating developments include and addition agents for patents on a sulfamic acid bath (%I), both fluoborate and sulfamate baths (28). Methods of plating tin-lead alloys from fluoborate baths have appeared in the German literature (m).
If one considers that 65% of all tin mill products are used for cans, perhaps references to two comprehensive books on canning technology (47, 81)would not be amiss. Britton (16, 16) of the Tin Research Institute has shown that the use of tin coatings on steel as a base for paints increases considerably the time elapsing before rust appcars and delays very strikingly the spread of rust from areas of damage to the paint. Means of determining the protective effect of lacquer films on tin plate have also been described in the German literature ( 7 1 ) .
TIN ELECTROPLATING
SOLDERS
There has been a considerable amount of development in this well established field. The spectacular tin electroplating line now in operation a t the Weirton Steel Company has been described in many places (5, 63). This line, illustrated on page 1951, coats, melts, and chemically treats tin coatings on strip a t 2000 feet per minute. Not to be outdone, other producers have introduced novel features on their own lines. The CarnegieIllinois Steel Company is using a “coating thickness meter” on its electrotinning lines t o control coating thickness (19‘). The meter combines the electrical values of plating current, strip speed, strip width, and plating efficiency in a precision circuit to record thickness of coating. The equipment may be set to control coating weights. In the alkaline tin-plating process, which is used by many commercial tin-plate producers, a tin anode of high efficiency containing 1%aluminum has been developed (87). Eleotrodeposition of tin from stannous fluoborate baths has been studied by the Tin Research Institute (80). A t present, the advantages of high rates of deposition of the fluoborate bath are overshadowed by the sludging problem. There have been
Solders are, next to tin plate, a most important user of tin. Both the National Bureau of Standards and British Standards Institute have recently published bulletins on solders (14, 76-77). Soldering by induction heating methods has become an established method for a wide range of applications, particularly where small lot production is involved (63, 78). Barber (7) has not only covered a method of evaluating solder but has shown that the joint strength increases to a maximum at 60% tin. He has shown that, contrary to general belief, a small amount of silver is not equivalent to a large amount of tin. Similarly, antimony is not a substitute for tin but might, with certain restrictions, serve as a substitute for lead. Cadmium might also be similarly considered. He found that bismuth in appreciable amounts cause8 brittle joints. Cady (17) has scotched a popular belief by showing that soldering does not affect the properties of cold-rolled copper. Information on creep strength of solder have a p peared in the German literature ($7). Methods of analysis for tin-lead solders have recently been published (84). Other developments include an anojired aluminum soldering iron
GENERAL TIN PLATING
Donelson (24) has developed a unique device, the “hydrophil balance,” which measures the amount of oil on tin plate quickly, thus getting around what has been an elaborate and costly control method. The American Iron and Steel Institute has issued a revised edition of the “Tin Mill Products Manual” (2). Fundamentals of tin-plate production have been recently brought up to date (66) and an economic survey of the tin-plate industry in Western Europe has been made (2.9). TIN PLATE APPLICATIONS
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October 1950
INDUSTRIAL AND ENGINEERING CHEMISTRY
tip which does not pit (88),new aluminum solders (87), and soldering methods (1). TIN BRONZES
Although tin bronze is considered a copper alloy, and rightly SO, because the tin content rarely exceeds lo%, i t is a major use for tin. Accordingly, the Tin Research Institute has done a considerable amount of investigation on improved casting methods. Pell-Walpole and Kondic (81) have investigated semicontinuous cmting. The objective is a machine which produces chill-cast solid or cored rod in much the same manner as the Asarm (8496) continuous process, but is of simpler construction to permit quick and economical changes of alloy and section. Other work directed toward the improvements of bronze cmting includes that Frear (Sf?), and Lepp (68). of Bond-William ( f d ) , Glaisher ($4, O’Keefe and Taylor (78) have devised a simple fracture test which not only indicates unsoundness but is unique in that it shows whether the unsoundness is caused by shrinkage, improper melt quality, or gas pickup from wet or unsatisfactory molds. Showell (94) has examined the influence of various factors on the hot working of phosphorized tin bronzes. CERAMICS
A unique use for tin has stemmed from the electrical conductivity properties of stannic oxide. Electric conductive glass useful for heating applications is being marketed commercially by two companies (70). Such glass is heated by a transparent film of stannic oxids fused to the glass surface, which acta as a resistance heating element. An analogous development is the use of stannic oxide with uranium oxide in electrically conductive glass electrodes (73). Conditions for producing a good chrome-tin pink underglaze have been noted (13). MISCELLANEOUS TECHNOLOGICAL DEVEWPMENTS
In this difficult-to-classify category may be found such diverse items as a comprehensive publication covering fusible alloys (97), replacement tin coatings on aluminum using fluoride baths (48), and the use of tin undercoats to prevent spotting out in brassplated aluminum castings (48). BASIC RESEARCH
The distinction between technological development and basio research is sometimes hard to make. The objective of technological development is the immediate improvement of man’s material condition. The touchstone for determining what is basic research is whether or not the objective is the better understanding of natural laws. The following fit into this category. Campbell, Wood, and Skinner (18) have studied the liquidus of the iron-tin system and have found that the solubility of iron in molten tin at various temperat,ures is not nearly so great as the present handbooks would have us believe. This is an important finding from the practical standpoint of control of bath purity in hot tinning. There has been a considerable amount of investigation on the phase diagrams of tin alloys (64,86, 90-98, 96). In addition to this, Hedges (41) has collected equilibrium data for 36 binary tin alloys. Tin nonmetal systems have also been investigated (98, 89, 108). Kondic and Kozlowaki (69) have used tin and tin-lead alloys in their study of the fundamental characteristics of casting fluidity. Dunkerley (96)and his m c i ates have continued their investigations of the low-temperature properties of tin binary alloys. Studies of the crystal structure of tin (6, 11), of the surface tension of tin and tin-sodium alloys (8S),of tin corrosion (N),and of electrocapillary phenomena of tin alloys (68) have been undertaken. Tin as a supraconductor (81, 33, 61, 66, 101) has received considerable attention. The magnetic momenta of Sn116 have been measured using the nuclear induction spectrometer (86).
2021
REFINING AND RECLAMATION
Jones (66)has written what is probably the most inlormative paper on the purification of tin and tin alloys to appear to date. New fire refining (6069,68) and electrorefining processes (SI, 49, 100) have also appeared in the literature. Tin reclamation continues from residues (4,6) and from tin-plate scrap (6’7,60,69) to receive attention. LITERATURE CITED
Aktien-Gesellschaft Brown. Boverie & Cic, Swiss Patent 241,717 (Aug. 16,1946). -4merican Iron 8E Steel Inst., “Steel Products Manual. Tin Mill Products, Section 14,”August 1949. Anon., Iron Age, 165, 106-7 (April 27, 1950). Arend, A. G.,Can. Metals Met. Id.,12,18-19.36 (June 1949). Arend, A. G.,Mine & Quamy Eng., 15,23-6 (1949). Aust, K. T., and Chalmers, B., Proc. Roy. SOC.,201A,210-15 (March 22, 1960). Barber, C. L., Am. Machinist, 93, 110-13 (May 5, 1949). Barton, H. K.,Die Castings, 7,43-4,46,68 (June 1949). Bennett, P. S.,J . Electrodepositors’ Tech. SOC..26,No. 6 (1950). Ibid., No. 7. Boas, W., and Fensham, P. J., Xature, 164, 1127-8 (Dec. 31, 1949). Bond-Williams, N. I., J. Inat. Met&, 75, 349-53 (1949); Tin Research Institute publication, January lQ49. Bose, H. N.,Trans. Indian Ceram. SOC.,7,28-31 (1948). Brit. Standards, 219 (1949). Britton, S.C.,Oil & C o h r Chenista’ Assoc., 33,125-34 (March 1950). Britton, S. C., Paint Munuf., 19,95-6 (1949). Cady, E. L.,Materials & Methods, 30,75-6 (August 1949). Campbell, A. N., Wood, J. H., and Skinner, G. B.,J . Am. C h m . SOC.,71, 1729-33 (1949). Carnede-IllinoisSteel Corp., Iron & Steel E w . , 27,No.1, 1612 (January 1950). Clifton, F. L., U. 8. Patent 2,489,523(Nov. 29, 1948). Condon, E. U., and Maxwell, E., Phys. Rm.. 76, No. 4, 578 (1949). Crombie, J. N., “Tin Plate. Part 1. A Glance at Hot Dipped and ElectrolyticTin Plate. Part 11. Coating of Hot Dipped Tin Plate,” American Iron and Steel Inatitute, “Technical Committee Activities,” pp. 129-71, 1949. Damiron, Paul, Iron Steel Eng., 26,76-81 (August 1949). Donelson, J. G., Modern Packaging, 23, 126-6 (March 1950). Dunkerley, F. J., Hunter, H. B., and Stone, F. G., Metals (Trans.),1 (Trans. Am. Inst. Mining Met. Eng., 185,1005-16 December 1949). DuRose, A. H., and Little, J. D., U. S. Patent 2,460,252(Jan. 26, 1949). Efendiev, G. A,, Zhur. Tekh. Fiz., 18,1159-65 (1948). Eng. Mining J., 150, 146 (July 1949). Erdmann, R., MetalloberfEache,76,No. 2,293-5 (1949). Ference, G. E.,et al., J. Am. Oil Chemisto’ SOC.,27, 122-7 (April 1950). Ferrante, Corrado, Metallurgia italiana, 41, 190-8 (JulyAugust 1949). Frear, C. L., F o u d r g , 78, 126-7. 288-92 (May 1950). Fritz, J. J., Gonzaler, 0. D., and Johnston, H. L., Phys. Reo., 76, No. 4, 580-1 (1949). Glaisher, W . H., J. Inst. Metals, 76, No. 4,377-87 (December 1949). Glayman, Jacob, Fr. Patent 866,947(Sept. 18,1941). Glock, C. E., U. S. Patent 2,460,608-9(Oct. 6, 1948). Grassmann, P., Z . Metallkunde, 40, 156 (1949). Gray, A. G.,Gresham, W. F.,and Loder, D. J., W. S. Patent 2,461,607(Feb. 15,1949). Haase, L. W., Metalloberfl(lch6,2, 166-8 (August 1948). Harris, E. F.,U. 6 . Patent 2,450,794-6(Aug. 5, 1948). Hedges, E.S.,“Equilibrium Data for Tin Alloys,” Greenford, Middlesex, England, Tin Research Institute, 1949, TN793 T49e. Heiman, Samuel, J. Elaotrochem. SOC.,95,206-26 (1949). Hipperson, A. J., and Teanby, P. M., Welding Research, 3 (bound with Trans. Inst. Welding, 12), 86r-92r (October 1949). Hoare, W. E., “Hot Tinning,’’ Middlesex, England, Tin Research Institute, 1948. Hoff, C. M. (to National Steel Corp.), U. S. Patent 2,490,055 (Dec. 6,1949). Hoffman, R. A,, Ibid., 2,467,152(Dec. 28,1948). Howard, A. J., “Canning Technology,” Washington 13,D. C., Sherwood Press. 1950.
