•
EQUIPMENT
Stick Tight fo Titanium Remove the oxide, replace with fluoride — k e y to better bonding of titanium to coating metals
JTXDHEBEÏ^T PROTECTIVE COATINGS have
been successfully electrodeposdted onto titanium b y National Bureau of Standards. The process may well lead to the further use of titanium in many equipment applications, particularly at high temperatures, the bureau feels. These electrodeposited coatings are aimed at overcoming the two major disadvantages of titanium—its tendency to seize or gall in loaded contact with itself or other materials and its oxidation at elevated temperatures. Coatings of such metals as nickel or chromium could reduce these problems; up t o now, though, scientists could not get the metals to stick to titanium. This lack of adhesion has been blamed on the presence of an oxide film on the titanium surface. However, attempts to remove this film by the con-
ventional acid etch or anodic film approaches did not improve t h e bonds. C. L. Stanley and A. Brenner of NBS staff, still believing that these oxide films were the source of adhesion troubles, set to work to prove it. First they placed a small piece of titanium in a glass tube, added silicon carbide and ceramic balls, evacuated the tube, and sealed it. They then tumbled the tube for several hours to abrade the titanium surface. Next the tube -was placed in a chromium plating bath and crushed under the bath surface—preventing contact of the titanium with the atmosphere. A control specimen was carried along, the only difference between it and the test being that the control tube was left open to the atmosphere. The adhesion of t h e two specimens
was measured. The specimen held without air showed distinctly better adhesion than the control. The film theory was upheld. The next step was to develop some practical means of removing the oxide film and preventing its being reformed during handling. After they had examined a number of methods, Stanley and Brenner came up with a pretreatment procedure which formed a coating of titanium fluoride on the titanium surface. This procedure led all others in bond strengths obtained. The method provides a coating which prevents formation of the oxide film, according to Stanley and Brenner. And, when the specimen is placed in the chromium plating bath, the fluoride film dissolves away, leaving the clean titanium surface and allowing the chromium to bond directly to the base metal. A two-minute heat treatment at 800° C. in an inert atmosphere further improves the bond. Tensile strength tests on heat treated * specimens show that the strength of the bond between chromium and titanium ranges from 4000 to 18,000 p.s.i., somewhat less than the tensile strength of heat treated chromium itself. However, in all these tests, the bureau says, the fracture occurred in the chromium plate and not between the two metals, which is indicative of the bond strength obtained. Similar procedures have been developed for depositing nickel and copper on titanium. However, the nickel and copper deposits have not adhered as well as chromium and have frequently blistered.
Single Crystal Puller In keeping with the increasing demand for germanium and silicon (C&EN, Nov. 19, 1956, page 5766), Precision Tool & Engineering has designed and is manufacturing a machine for pulling single crystals of these materials. Production rates as high as 3 0 0 gr is of single crystal silicon and 1000 grams of single crystal germanium per 8-hour day have been reported, the company claims. The crystal puller is equipped with several controls for improved operation. Hence, after the charge of silicon or germanium has been prepared, only about 10 minutes are needed to position the charge crucible, close the system, flush it with an inert gas, and position the induction coil. When the crystal has been pulled, the crystal and seed can be removed after about 15 minutes * for cooling and three minutes for dis- This scale model demonstrates Griseom-RusselTs design of a liquid metal heated assembly. steam generator for nuclear power generation system. The heat exchanger feaFor silicon, a 10-kw. heater is tures double tube construction to separate molten metal from steam and water. * "ed; for germanium, only a 5-kw. Intermediate space is monitored for leaks. Ε 1 heater is needed. Water requirement 6330
C&EN
DEC. 24.
1956
Visible economies at Standard Oil Company of California's n e w ammonia slant include the high pressure reforming un£r, which greatly reduces compressor costs/ skeleton-type, economical outdoor construction; and permanent, labor-saving dmrrkk for handling] catalyst.
CHEMICAL
S
New 711
T H I R D
A V E N U E ,
N E W
DIVISION
Text Y O R K
17. Ν.
Υ.
A SUBSIDIARY OF PULLMAN INCORPORATED T h e Canadian Kellogg Company Limited, Toronto · Kellogg International Corporation, London Companhia Kellogg Brasileira, Rio de Janeiro · Com pa nia Kellogg d e Venezuela, Caracas Kellogg Pan American Corporation, New York · Société Kellogg, Paris
New Text
SPRING S T E E L CLIPS
TANK
STAINLESS S T E E L N U T
LININ(
TITANIUM
New Text thermowell SAVES «10,000 A thermowell, used in a chemical reaction vessel at DuPont, wras failing about every nine months from severe corrosion, even when fabricated from one of the best of the standard corrosion-resistant metals. The en vironment was dilute nitric acid and nitrogen oxide at temperatures exceeding 400F. Titanium was suggested as a material of construction. But, since such a unit would cost $300 against $95 for the existing installation, a careful total cost analysis was made. T h e findings were startling: DuPortt corrosion engineers discovered that each time a thermowell failed, it cost the company $1500 in lost production and replacement labor. They estimated a service life for the titanium ther mowell of a t least five years (five to ten times as
long as the other corrosion resistant material) re sulting in a saving of about $10,000.
As this case history shows, titanium's corrosion-resist ance often makes it by far the most economical material. Yet, this versatile metal offers additional outstanding advantages . . . each sufficiently important t o recom m e n d it to designers and engineers, For example, tita nium is unusually resistant to erosion by high-velocity fluids and to stress-corrosion cracking . . . withstands abrasion, shock and fatigue . . . has a uniquely high strength-weight ratio that means substantial reduction in weight and cost of material needed for a given use. When the going is tough for ordinary metals — try REM-CRU titanium. For specific recommendations, call or write REM-CRU today. To keep abreast of the latest develop, tents on this vital metal* tcrite to DepU CIS-12 for the Rie m-Cru Review—a free periodical presenting the latest technical data on ti tanium alloys.
TITANIUM
REM-CRU TITANIUM, INC., MIDLAND,PENNSYLVANIA
Sales Offices: 3338 South Malt Avenue, Los Angeles 22, California
6332
C&EN DEC. 24, 1956
·
4501 W. Cortland Street, Chicago 39, Illinois
405 Lexington Avenue, New York 17, Ν. Υ.
EQUIPMENT
for the puller is 1 gal. per min. at 30 p.s.L; for the industion heater, a supply of 6 gal. per min. at 4 0 to 8 0 p.s.i. is necessary. About 6 liters of inert gas per minute are required during pull. E2
• Allis-Chalmers has extended its line of paper stock pumps to include a 72in. model. A-C's 20-in. pump is rated at 15,000 gal. per min. at 50-ft. head. E3 • Electrophoresis apparatus, available from American Instrument, separates protein mixtures and records absolute concentration of components with a maximum error of 2 % , Aminco says. E4 • Thermistor-actuated
temperature
controller has been developed by As sembly Products to act on a tempera ture change as small as 0.075° F. Practical temperature limits are —75° t o 300° C , according to the company.
regulator is available in sizes from V 4 in. t o 4 in. and in temperature ranges between 2 0 ° and 455° F. E9 • Microscope slides, distributed by Sci entific Products, are n o w packaged in a tilt-top box for easy removal of indi vidual slides. 110 • Tarpaulin material of improved abra sion resistance has been a d d e d to D u Pont's line of neoprene coated fabrics. Abrasion resistance is obtained b y a coating of Hypalon on t h e under side of the fabric. Ell • Sight How indicator, designed for indication of leakage flows or other small flow requiring constant checking, is n o w available from T h e George W . Dahl Co. in flow ranges of 0 to 2 cu. ft. per hr. Ε 12 • Explosion-proof
pressure-vacuum
control, by United Electric Controls, is designed for use in Class I, Group C
and D locations. Ranges of pressure between 0 and S0O p.sJ. with on-off differentials between 2 and 3 0 p.s.i. are obtainable. Ε 13 • Mixer for blending catalysts and ad ditives without entrainment of air is now available from Pyles Industries. There are five models, w i t h capacities from 1 quart to 5 quarts. Ε 14 • Deaerators with redesigned head sec tions are now in production b y LA Water Softener. Tîie new design features accessibility for cleaning, improved venting, better baffling of vent discharge, t h e company says. Ε 15
I
Further useful înformafton on keyed Equipment mentioned is readily available . . .
• Use handy coupon on page 6334
^
December 2 4 , 1 9 5 6
E5
ί Testing oven with controlled tem perature and humidity has been de signed b y Electric Hotpack for testing of chemicals, plastics, and other ma terials under controlled conditions.
U s e this h a n d y s e l f m a i l e r to o b t a i n f u r t h e r i n f o r m a t i o n o r literature. Simply mark, dip coupon, fold, and
E6
Every week C&EN's editors survey a l a r g e volume of valuable scientific, technical, a n d business Information issued in the form o f product announcements, booklets, catalogs, d a t a sheets, etc. This material is digested and presented in several departments. For your convenience this coupon is provided t o facilitate requests f o r further information on these items as well as on products and services mentioned in advertisements.
• Fume h o o d with an air scrubber to remove acid vapors and other watermiscible vapors and fumes has been developed b y Hamilton Mfg. Because the exhaust gases are scrubbed, ducts need not be made of corrosion resistant materials and air pollution problems are reduced, the company says. Ε7 • Temperature regulator of stainless steel is being offered by RobertshawFulton Controls for applications where corrosion resistance is needed. The
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φ Elecfropolarizer Initial voltages rrom —3 volts to —1 volt and polarization through any span from 0.25 to 3 volts can be obtained with Patwin Instrument's G-l Record ing Electro-Polarizer. Ε8
Chemical a n d Engineering News 4 3 0 Park A v e n u e N e w York 2 2 , Ν . Υ.
