posits are brittle but become ductile w h e n heated. These are harder than the o r dinary electro-deposited nickel, a n d u p o n heating their hardness is still further i n creased, in contrast to the behavior * >f " h a r d " elect rodeposited nickel.
Products and Processes Electraless
Plating
an
Metals
Λ new method for plating' nickel and cobalt on metal surfaces without the use of electric current has been developed by Abner Brenner and Cîrace Κ. Hiddell of the National Bureau of S t a n d a r d s . T h i s proc ess, known as elect roless plating, is brought about by chemical reduction of a nickel or cobalt salt with hypophosphite in hot solution. T h e reaction is catalytic, and under the prescribed conditions of concentration and pIT, no plating occurs unless certain metals, such as steel or nickel, are in troduced in the b a t h . T h e reduction then occurs only on the surface of the immersed metal with the production of an adherent coating of 93 to 9 7 % purity. Photomicrographs of deposits obtained in this way show both a laminar and a columnar structure, similar to bright nickel electrodeposits. The» electroless deposits are of good quality -sound though brit tle, and usually bright. Since they can be made as hard as tool steel, the method may prove useful when? hard, wear-resist a n t surfaces are required, as in bearings. T h e process is particularly applicable to the plating of recesses, irregular-shaped ob jects, and enclosed areas such as tubes, where a centered internal electrode with special current leads would be needed in electroplating. T h e equipment is simple a n d more easily assembled than t h a t required for electro plating. Xo generators, rheostats, special racks, or contacts are necessary. Small p a r t s which cannot be barrel-plated eco
by
Chemical
Wax from Reduction
nomically are readily plated by t he electroless process if suspended by a string or in a bag affording a m p l e exposure of t lie metal surface of the solution. There is no nrcil of constant motion, as in barrel plating, since current distribution is not involved. While electroless deposits of cobalt and cobalt-nickel alloys have been obtained only from a m m o n i a c a l solutions, nickel can be deposited from either acid or alka line solutions. T h e reactions, requiring a t e m p e r a t u r e above V)0° C , are given in the following equations (in which cobalt may be written for nickel): XiCT, + NaH 2 P(> 2 + li,() >• ΝΊ + 2HOI + XaHoPOa or XalloPO, + H 2 o >• X a H 2 P 0 3 + Η« T h e first reaction is the important one, resulting in t h e deposition of nickel; the second reaction tends to lower t h e effi ciency of the process through oxidation of the hypophosphite. A unique feature of the elect roless proc ess is the catalytic initiation of t h e reac tion by t h e following metals: iron or steel, nickel, gold, cobalt, palladium, and a l u m i n u m . ' Unless one of these metals is introduced into t h e solution, no reaction takes place. Once started, the reaction continues a t t h e metallic surface a n d only rarely occurs in other parts of t h e b a t h . For this reason, the containing vessel should be of glass, plastic, or other noncatalytic material. As formed, the electroless nickel de
Sugar
Cane
A practical starting point for r e c o v e r i n g the valuable hard wax t h a t forms a t h i n coating on growing sugar cane has b e e n found by the Γ . S. Department of Agricul ture. Scientists working at the l l o u n i a , La., laboratory of the Bureau of Agricu.1tural and Industrial Chemistry h a v e worked out an «. rronomical solvent process for the recovery of the crude wax and f u r ther solvent t r e a t m e n t s for s e p a r a t i n g fats from.the wax and purifying the w u x . T h e process for recovering the wax a n d other by-products is now being d e v e l o p e d commercially on a small scale. En general, sugar-cane wax resembles carnauba wax, the basic ingredient of higziigrade wax polishes, which for years has b e e n an important import item and was in special d e m a n d during the war. A ton of sugar-cane betirs only 2 or 3 l b . of wax, making direct recovery of the w a x too expensive by any physical or chemical method. Working at t h e Houina l a b o r a tory, R. T. Balch and C. 13. Broeg a t tacked the wax problem a.t the point w h e r e the wax is concentrated i n the waste filterpress cake that remains after clarification of the cane juice. In making sugar, t h e juice is treated with lime and is settled a.xid the sediment is filtered. The r e s u l t i n g waste press cake is used for fertiliser. Removal of the wax a n d fat would nif*.ke it a better fertilizer. Tn the view of investigators, t w o courses of development are possible. Large s u g a r mills m a y find it practical and profitable to process their own press cake just a s it comes from the sugar mill without need for
Photornicrograplis of electroless nickel deposits from acifl solution. A. IWickel as deposited, showing laminations and columnar structure: hardness 500. B. After annealing at 400 ° C. for 30 minutes producing maximum hardness of 800. C. After annealing at 600 ° C. for 30 mi η utes, showing precipitation. D. After annealing for 30 minutes at. 800° C , showing excessive precipitation; hardness 470 (Krioop scale). Right. Nickel plating on a steel strip. Electroless plating equip ment consists of glass vessel * solution, and immersion heater 2222
C H E M I C A L
A N D
ENGINEERING
NEWS
drying. Or, it m a y prove more practical to develop wax recovery as a centralized industrial undertaking operating the year round and using dried press cake from m a n y mills. In either case, the products from the establishment would be: t h e extracted cake having improved fertilizer value; the wax, which would be refined to t h e degree required by the use for which it is intended; the by-products from, t h e fatty fraction; and the dark wax or " p i t c h . " I n the main, the last two items are still of speculative value but have interesting possibilities as a basis for further research. The sterols from t h e fatty fraction, for example, have possibilities in the vitamin field and in cosmetics. If all t h e filter-press cake from sugar mills in t h e United States, Hawaii, Cuba, a n d P u e r t o Rico were processed for wax recovery, it is estimated t h a t the recovered wax would a m o u n t to considerably more t h a n the total q u a n t i t y of hard waxes used annually in the United States in t h e prewar years.
Finish for Polystyrene
Plastics
Development of a successful line of clear a n d colored surface finishes for polystyrene plastics has been reported by t h e M o n s a n t o Chemical Co., Everett, Mass. Coating chemists a n d plastic technicians h a v e reported t h a t t h e lacquers overcome the tendency of solvents to produce crazing in polystyrene. T h e lacquers are either clear or pigmented, resistant to oil, a n d will protect the polystyrene. T h e y were developed t o m a k e possible the coating of the face or the back of the clear moldings in color a n d to provide wipe-on colors for dials, t r a d e - m a r k s , a n d decorations. T h e lacquers can be spra3 r ed onto t h e polystyrene surfaces a n d will d r y rapidly to a hard, adherent, a n d mar-resistant finish of high gloss suitable for a n exterior finish. T h e wipe-on coatings or coatings applied t o inlays, such as dial numerals, letterings, and designs, are usually applied with a brush.
Durable
Electric
2 5,
NO.
Copies of the following reports can be obtained at the prices indicated from the Office of Technical Services, Department of Commerce, Washington 25, D. C. Orders should be accompanied by check or money order, payable to the Treasurer of the United States. A supersonic testing method developed in Germany during the war can locate bubbles in sheet metal which are too minute for detection by x-ray or magnetic techniques according to report P B 25,556 (photostat, SI.00; microfilm, $1.00; mimeographed, 25 cents; 8 pages). Sheet metal is tested by comparing the energy of supersonic vibrations before and after passage through the metal. Any more than the normal drop in transmission indicated the presence of a fault. Tests show that a bubble only 0.00001 mm. in diameter can increase the drop a hundredfold. Though a bubble filled with slag or rust does not cause so great a drop, it is nonetheless easily détecter I. F o r generating supersonic vibrations the lleichs-Roentgenstelle uses a 15-wattquartz crystal sender operating a t 1,000 kilocycles and "wobbles" the frequency 100 cycles per second to avoid standing waves in t h e test metal as well as between the sender and receiver. T h e vibrations are transmitted by means of a metal block
to a narrow chamber of running water. The water makes contact with one edge of the test metal, thereby passing on the vibrations. A similar water contact at the opposite edge of the; metal picks up the vibrations and forwards them to the receiver. The sending a n d receiving units are mounted on opposite ends of a long pair of tongs. In operation, t h e tongi* straddle the test metal a n d move along its edges. Hand pressure or springs in the tong handles keep the ton»· ends in contact with the met ai. ( iernian anodic oxidation methods for forming a protective oxide film on aluminum and aluminum alloy products are described in report P B 49,275 (photostat, §3.00; microfilm, $1.00; 33 pages including diagrams). Seven companies used an anodizing process requiring a sulfuric acid b a t h as the electrolyte and a direct current source as the power supply. Seventy per cent of all anodizing work in Germany involved the use of this process. A company a t S t u t t gart favored using alternating current with sulfuric acid in anodizing porous sand eastings which t r e a t m e n t helped reduce, pitting and produced a soft ductile film. For a ductile oxide coating on aluminumcopper alloy castings, the company used oxalic acid for the electrolyte a n d alternating current of relativel\ r high voltage.
DEPENDABLE FOR HIGH VACUUM PUMPS
Specially
Processed
For H i g h V a c u u m
Cords
T h e wire and cable d e p a r t m e n t of U. S. R u b b e r C o . has introduced a line of portable electrical cords featuring a heavyd u t y neoprene rubber jacket t o provide increased protection against abrasion a n d damage. T h e thickness of the new jacket h a s been increased 30 to 6 0 % without increasing t h e over-all diameter of the cord. Laytex is applied b y a dipping process which produces a thinner insulation with superior physical and electrical properties. T h e new cords are designed to withstand extreme flexing, constant movement a n d surface abuse, and are intended for use on tools, washing machines, portable lamps, sound equipment, refrigerators, heaters, a n d other electrical equipment. V O L U M E
OTS Reports
31
»
»
New C e n c o l l y v a c Oil is specially processed to assure maximum vacuum p u m p ing speed a t low pressures when using Cenco and other mechanical vacuum p u m p s . It is the result of'exhaustive tests made in the Cenco laboratories on the physical properties of a wide variety of vacuum-pump oils. D a t a taken from these tests show a n increase in pumping speed of more than 10% over that obtained from the former Cenco Hyvac Oil, a n d as much as 3 5 % over t h a t obtained from most other oils ο île red for vacuum p u m p use. Obtain maximum pumping speed a t low pressures in your newer models of Cenco llypervac-20, Cenco Mega vac, Cenco l l y v a c , and other vacuum pumps by specifying t h e new Cenco l l y v a c Oil. N o . 93050B N o . 93050C
C e n c o My v a c Oil iii q u a r t c o n t a i n e r s Each. C e n c o l l y v a c Oil i n g a l l o n c o n t a i n e r s . . . E a c h
. . C E N T R A I , y*
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ί &ienttâc' Newjork , BOStOI* - SanJ*an
